Dwarf planets may be small, but they're some of the most intriguing objects in our cosmic neighborhood.

These icy bodies orbit the sun just like the major planets, yet they follow their own rules, often traveling along elongated paths far beyond Neptune. Their distant homes in the Kuiper Belt and scattered disk make them difficult to study, but every new mission reveals something surprising.

As you dive into this word search, you'll encounter the names of these fascinating dwarf planets.

Think of this quiz as your own mini‑expedition to the outer solar system —no spacecraft required.

See how well you score below!

Scientists have detected methane gas on the dwarf planet Makemake, indicating that the distant body is a dynamic icy world.

The discovery was made by a team led by the Southwest Research Institute (SwRI) using NASA's James Webb Space Telescope (JWST).

Makemake is one of the largest and brightest worlds beyond Neptune, and becomes only the second trans-Neptunian object, after Pluto, found to have a confirmed presence of gas.

"The Webb telescope has now revealed that methane is also present in the gas phase above the surface, a finding that makes Makemake even more fascinating," said SwRI's Silvia Protopapa, lead author of a new paper soon to be published in The Astrophysical Journal Letters, in a statement.

"It shows that Makemake is not an inactive remnant of the outer solar system, but a dynamic body where methane ice is still evolving," Protopapa added.

Makemake is about 890 miles (1,430 kilometers) in diameter, meaning it is two-thirds the size of Pluto. JWST made the methane find by picking up a telltale spectral signature of solar light re-emmitted by methane molecules.

The finding of methane in gas form could be due to either the presence of a tenuous atmosphere on Makemake, or a more transient activity such as that experienced by comets when its volatiles sublimate, or from cryovolcanic plumes, according to the study authors.

The detected atmosphere, if it is indeed a permanent feature of Makemake, is very tenuous. Its surface pressure is only about 10 picobars, or 100 billion times below Earth's atmospheric pressure, according to the authors' models.

The authors produced models for a scenario in which methane is released in plume-like outbursts. These simulations suggest that methane could be released at a rate of a few hundred kilograms per second, making the level of activity comparable to the water plumes on Saturn's ocean moon Enceladus.

"Future Webb observations at higher spectral resolution will help determine whether the methane arises from a thin bound atmosphere or from plume-like outgassing," said Ian Wong, staff scientist at the Space Telescope Science Institute and co-author of the paper.

Earlier observations of Makemake made when the icy world passed in front of a star had shown that it did not harbor a significant atmosphere, but did not rule out a much thinner one.

The paper, titled "JWST Detection of Hydrocarbon Ices and Methane Gas on Makemake," is available on the preprint repository arXiv.

The odd dwarf planet Quaoar might have a brand-new moon. Observations of the tiny world, made by a pair of astronomers in California, suggest it possesses either a second satellite or a third ring.

Quaoar and our solar system's other dwarf planets are generally so far away that they are a challenge to view directly from Earth. (An exception is Ceres, which lies in the main asteroid belt between Mars and Jupiter.) So, to observe them, astronomers rely on stellar occultations — moments when an object passes between them and a background star. The body of the foreground object briefly blocks light from the star, as do any rings or satellites.

Both of Quaoar's known rings were discovered in separate occultations, with the first ring initially identified by a trio of amateur astronomers.

But occultation observations can be tricky. Seeing rings depends on the angle of their orbit, which can miss the star completely. And moons must be in the right position in their journey around their parent object to block the star, so spotting them can be hit or miss. And occultations themselves depend on the viewer's location on Earth, as the viewing angle shifts with latitude.

On June 25, 2025, Rick Nolthenius, an astronomer at Cabrillo College in Aptos, California, and his former student, amateur astronomer Kirk Bender, set out to observe the Quaoar system during an occultation. The roughly 680-mile-wide (1,090 kilometers) dwarf planet would pass in front of the background star at an angle visible only to observers in northern Canada and other parts of the Arctic during daylight hours. But one of the rings might manage an occultation that could be seen from California. It was enough to send Nolthenius and Bender south to the Monterey Institute for Research in Astronomy, where an observing partnership was set up.

With Nolthenius on the institute's 36-inch telescope and Bender on the 14-inch one, they anxiously awaited the potential passage.

"I did decide to start the recording earlier," Nolthenius told Space.com. "I thought, Who knows what we're going to see?"

So they had their separate systems up and running four minutes before the anticipated occultation. Their optimism paid off.

"I said, 'Oh my God, did you see that? The star disappeared,'" Nolthenius said.

It was a brief flicker, lasting just over a second, and Bender hadn't seen it. But both telescopes did. The recordings showed a brief 1.23-second blip.

"The profile of the occultation was most consistent with it being a new satellite — a new moon — going around Quaoar," Nolthenius said.

The results were published this past August in an article in the journal Research Notes of the American Astronomical Society.

'Keep recording'

Quaoar was discovered in 2002. The dwarf planet orbits beyond Pluto, taking 286 Earth years to complete one lap of the sun. Its name comes from the creation mythology of the Tongva people, who are indigenous to the Los Angeles Basin, where the initial observations were made. The name can be pronounced with two syllables (/ˈkwɑːwɑːr/) or three (/ˈkwɑːoʊ(w)ɑːr/).

In 2007, Quaoar's only confirmed moon, named Weywot, was spotted. The dwarf planet's rings are a puzzle. The pair orbit a significant distance from the icy world, farther out in relation to the dwarf planet's size than expected. Their extensive reach required astronomers to revise what they thought they knew about the survival of planetary rings.

It's possible that the new observations by Nolthenius and Bender indicate not a moon but a third ring. The duo have been cautious in their classification, allowing for the possibility that a torus of material could be behind the observations. But Nolthenius doesn't think that's likely.

"As soon as I saw that occultation, I decided, OK, we're going to keep recording," he said.

The pair continued to observe for a full three minutes after the planned occultation time, for a total time of nine minutes. They saw no sign of a second occultation, which they would have expected had a ring been involved. However, the duo still doesn't rule a ring out as a possibility.

Study co-author Benjamin Proudfoot, an astronomer at the University of Central Florida, also thinks that a newfound satellite is the most likely explanation. Proudfoot observed Quaoar in 2024 using NASA's James Webb Space Telescope, work that allowed him to place constraints on the ring system in a paper published earlier this year in The Planetary Science Journal.

"We think we found a new moon," Proudfoot told colleagues in July at the Progress in Understanding the Pluto Mission: 10 Years after Flyby conference in Laurel, Maryland, where he reported the discovery.

Checking the boxes

Rings and moons aren't the only potential explanations for blockages seen during occultations. Nolthenius and his colleagues had to rule out several other possibilities.

Perhaps the easiest was an airplane flying overhead. In addition to Nolthenius and Bender, a handful of other observers were present, and they watched the area of the sky for aircraft; none were spotted in the region during the occultation. A large bird could theoretically block both telescopes, and Nolthenius said that California condors are native to the region. But "they don't hover," he said, and that would be necessary to block both telescopes for more than a second.

What about a drone, which could easily manage the feat? Nolthenius pointed out that such a craft would have to be very large, at least 80 inches (200 centimeters) wide, and would have to be precisely targeted to hover in such a way that it would block both telescopes — in other words, sent to "mess with those astronomers." It would have to move into position, stop on a dime, remain for less than two seconds, and then leave.

"That would take a drone mastery beyond what I think is possible," Nolthenius said.

The team then vetted objects beyond Earth. Satellites orbiting our planet would block out light for less than a second. Interference by known asteroids would have been identified by the International Occultation Timing Association, which provides times to interested parties for occultations around the world.

What about unknown asteroids? An asteroid that has remained undiscovered to date would have produced a shorter event, and it would be unlikely to block light completely, according to the researchers.

The final potential obstructor was the Quaoar's known moon, Weywot. But it was casting its shadow further south, from an observer's perspective; occultations it may have produced would have been seen from Costa Rica, not California.

According to Proudfoot's calculations, the newfound Quaoar moon — if it does indeed exist — is at least 19 miles (30 km) wide. It appears to be moving in a special orbit known as a resonance with the outermost ring, making three trips around Quaoar for every five made by the annulus. Those numbers are rough estimates, because they are based on a single observation.

Full confirmation will come as other astronomers make observations of the moon. But that could be a challenge.

"Right now, we have a pretty good idea of what its orbit should look like, but not where along that possible orbit it could be," Proudfoot told Space.com by email. Observing it again would essentially require a blind search. He said it's likely that the moon is only visible in a telescope like Webb when it is farthest from Quaoar, making it even more challenging to observe.

"It's on the bleeding edge of detectability," Proudfoot said.

Nolthenius hopes that more astronomers – professionals and amateurs – will turn their eyes to the skies to observe Quaoar's occultations. Right now, the dwarf planet is passing in front of a region of the sky filled with stars. Once it moves on, he said, occultations will be much less common for the next 200 years.

If the new moon is confirmed, Nolthenius will have the chance to name it. He indicated that he's considering naming it after "someone special to me," but he's not sure how to make that work with the International Astronomical Union's naming conventions. (Small objects in the outer solar system are generally named after deities associated with the underworld or creation). Regardless, confirmation will likely take some time.

Meanwhile, both Nolthenius and Bender will continue hunting for occultations of Quaoar and other targets. The pair plan to observe more than a hundred occultations this year, roughly the same number they hunted last year.

"It's a little microadventure," Nolthenius said of occultation hunting. "I get to go off and do some science and not think about anything else."

The first interstellar object to visit the solar system may have been a fragment of an icy exoplanet, research suggests.

When 1I/'Oumuamua was first spotted in 2017, astronomers quickly determined that it came from outside the solar system. But although it was initially classified as a comet from another star system, it may actually be the skin of an "exo-Pluto," a completely unexpected class of Pluto-like objects anticipated to visit the sun.

"Everything about this object is consistent with it being a slab of nitrogen ice like you see on the surface of Pluto," said Steve Desch, an exoplanet researcher at Arizona State University. Desch presented his findings in July at the Progress in Understanding the Pluto Mission: 10 Years after Flyby conference in Laurel, Maryland.

Instead of being a mix of water ice, rock and carbon-rich material left over from the formation of the solar system, 'Oumuamua appears to be almost pure nitrogen ice. And rather than being a compact ball, the visitor is more elongated than any known body in the solar system and starkly different from the interstellar Comets 2I/Borisov and 3I/ATLAS, the only other known interstellar visitors.

"'Oumuamua is in a different category of object," Desch told Space.com by email. "It's much harder to find, but there are a lot more of them."

"We weren't expecting objects like this"

Planets arise from the cloud of gas and dust left over after a star is born. The first few million years are chaotic as the growing worlds jostle for their place around the young star.

In the solar system, the dance of the giant planets cast out a wealth of material. Most of the icy stuff was ejected; scientists think the icy bodies in the Kuiper Belt beyond Neptune today make up only a small portion of the original ejecta. Early on, there may have been enough material to create as many as 2,000 Pluto-like objects, along with 6,000 other, larger dwarf planets, according to Desch.

"Each Pluto would have been pummeled with a Vesta-mass of material," Desch said at the conference, referring to the second-largest object in the asteroid belt. (The largest, Ceres, is also classified as a dwarf planet.)

These collisions would have carved out some of the outermost layer of the wannabe planets. Observations made by NASA's New Horizons spacecraft during its 2015 flyby suggest that most of Pluto's surface is made of nitrogen ice, with some water ice acting as "bedrock." Although some of this base layer was likely ejected as well, Desch and his colleague Alan Jackson, also of Arizona State University, used simulations to determine that most of the material scraped from the baby Plutos was nitrogen.

During the shake-up of the solar system, these objects would have been redistributed. Passing by the sun too often would have caused many of them to evaporate quickly. Some would have been hurled inward, toward the sun. Others would have been tossed outward by Jupiter’s gravity. A handful of that group may have been captured in the Oort cloud at the very edge of the solar system, but most would have ended up adrift in interstellar space.

If planetary dances are common around other stars — and a growing number of observations suggest that they may be — then fragments of exo-Plutos may be ejected alongside comets and full-size planets.

There are hints that some objects classified as comets may actually be chunks of Pluto. In 2018, a separate research team reported that the unusual chemistry of Comet C/2016 R2 hints that it might be a collisional fragment from a Kuiper Belt object. Two other comets, C/1908 R1 Morehouse and C/1961 R1 Humason, have similar nitrogen-rich compositions that could classify them as scrapings from a proto-Pluto.

In a pair of papers published in 2018 and 2021 in the Journal of Geophysical Research: Planets, Desch and Jackson more fully explored how the unusual properties of 'Oumuamua would be better explained by a fragment of a Pluto-like object than by a comet.

"Because we had hardly seen such objects in the solar system, we weren't expecting objects like this," Desch told Space.com. "But we should have. Fragments of icy surfaces from Pluto-like dwarf planets were almost certainly ejected from our solar system, and 'Oumuamua made us come to grips with how much material must have been ejected."

An unlikely comet

When astronomers first spotted 'Oumuamua, it didn't quite meet their expectations of an exocomet. Although its rapid speed was one of the first signs of its extrasolar origin, it was moving much more slowly than anticipated. Solar system comets are made of water ice, silicates and carbon-rich material, while 'Oumuamua was nitrogen-rich. At about 330 feet (100 meters) in diameter before the sun began to melt its ice, 'Oumuamua was also far smaller than most comets, which typically range from about a few kilometers to tens of kilometers in diameter.

Finally, the object had an unusual shape that puzzled astronomers. Eventually, they determined that 'Oumuamua didn't have the roughly spherical core typically seen in comets; instead, it was elongated, or "pancake-shaped," Desch said.

'Oumuamua's low speed could be explained by its ejection from a young star. As stars age, gravitational interactions with their neighbors provide an occasional speed boost. If a fragment from an icy world was ejected early, the star would be traveling relatively slowly, imparting that reduced speed to its expelled material.

The nitrogen-rich material also suggested a youthful lifetime. Exposure to cosmic rays erodes the nitrogen ice, leaving behind water-ice objects that are likely more plentiful. Desch and Jackson estimate that 'Oumuamua is less than 2 billion years old, and perhaps as young as 500 million years old. They suspect it came from a young system, perhaps in the Perseus arm, the closest spiral in the Milky Way to the sun's location in the Orion arm.

The short-lived nitrogen is what made 'Oumuamua so easy to detect. While the water-ice leftovers may be more plentiful, nitrogen ice shines more brightly. But it also evaporates easily; Desch and Jackson estimate that by the time 'Oumuamua was observed, it had lost more than 90% of the mass it had brought into the solar system.

Altogether, it looks as though chunks of exoplanets may be quite plentiful.

"I think these objects are strong support for the idea that fragments of Pluto surfaces are part of the population of things ejected from the solar system," Desch said.

Indeed, the prompt discovery of 'Oumuamua suggests that interstellar objects may be an order of magnitude more abundant than formerly thought. Desch said he expects astronomers will find many more interstellar visitors using the Pan-STARRS and ATLAS surveys that found 'Oumuamua and ATLAS, as well as the newly operational Vera Rubin Observatory. By studying objects from beyond the solar system, researchers may be able to understand more about the outermost dwarf planets.

"More observations of 'Oumuamua-like objects … would tell us a lot about the composition of Plutos," Desch said.

He pointed to observations from New Horizons that suggest our own Pluto may have had a thick coat of nitrogen ice that was lost by impacts and other processes over the 4.5 billion-year life of the solar system.

Ceres, the largest object in the asteroid belt between Mars and Jupiter, has long been cast as a frozen relic of the early solar system — quiet, airless, and lifeless. But new research suggests that billions of years ago, this dwarf planet may have harbored the right ingredients to support simple microbial life.

That's according to a new study using data from NASA's Dawn spacecraft that opens the door to reevaluating the habitability of similarly small, icy bodies in the solar system, scientists say. If Ceres ever was habitable, its window to potentially sustain life likely closed billions of years ago. Today, its surface is bitterly cold, with most of its underground water frozen into a thick shell of ice, with some remaining as a salty brine trapped below.

Yet data gathered by Dawn revealed hints of a more dynamic, complex past. Bright, reflective patches on the surface turned out to be salt deposits left by briny liquid that once seeped upward. Organic molecules, discovered in Ceres' soil, suggest the ingredients for life were also present. Until now, though, one piece was missing: a source of energy to sustain life.

A world gone cold

Ceres is small by planetary standards, measuring just 600 miles (960 kilometers) across, or about one-third the width of Earth's moon. Unlike icy moons such as Jupiter's Europa and Saturn's Enceladus, which are kept warm by the gravitational tug of giant planets, Ceres has no external energy source to prolong its habitability.

The new study fills that gap, scientists say. Using computer models, researchers simulated Ceres' interior over billions of years and found that, between 2.5 and 4 billion years ago, radioactive decay in the dwarf planet's rocky core could have generated enough heat to drive hydrothermal activity.

Circulating water within the planet would have reacted with hot, altered rock, carrying gases and minerals into a global ocean, creating chemical "food" for microbes — much like the hydrothermal vents that teem with life on Earth's sunless seafloor, according to the new study.

"On Earth, when hot water from deep underground mixes with the ocean, the result is often a buffet for microbes — a feast of chemical energy," Samuel Courville, a researcher at Arizona State University who led the new study, said in a statement. "So it could have big implications if we could determine whether Ceres' ocean had an influx of hydrothermal fluid in the past."

Even if life never took hold on Ceres, the discovery could help broaden the range of environments that could potentially be habitable. Unlike many ocean worlds orbiting giant planets, Ceres isn't powered by tidal heating, making it a simpler and more revealing case study of how small, icy bodies evolve. Because so many objects in the solar system are similar in size, researchers suggest they could have represented a common type of habitable environment in the solar system's early days.

The study also points to other candidates: icy worlds roughly the size of Ceres, including some moons of Uranus and Saturn, may have followed comparable evolutionary paths and hosted temporary oceans capable of supporting life before cooling into the frozen landscapes we see today.

A study of potential past habitability on Ceres was published on Aug. 20 in the journal Science Advances.

Beyond the familiar planets lies a fascinating frontier filled with icy worlds, mysterious orbits, and cosmic curiosities. These are the dwarf planets—small but mighty members of our solar system that don’t quite fit the mold of the eight major planets.

From the icy reaches of the Kuiper Belt to the mysterious depths of the asteroid belt, dwarf planets come in all shapes and sizes.

This quiz will test your ability to name them all—and maybe even learn a few fun facts along the way.

Whether you're an astronomy buff or just curious about space, this quiz will challenge your knowledge and spark your imagination. So grab your telescope (or just your brain), and let's see how many dwarf planets you can name!

Try it out below and see how well you score!

A potential new dwarf planet has been discovered in the outer reaches of the solar system, and its existence poses the greatest challenge yet to the hypothesis that a ninth planet lurks far from the sun.

"We were very excited to discover 2017 OF₂₀₁ because it was not expected at all," study leader Sihao Cheng of the Institute for Advanced Study in Princeton, told Space.com. "It's very rare to discover an object both large and with an exotic orbit."

"The object's aphelion — the farthest point on the orbit from the sun – is more than 1,600 times that of the Earth's orbit," Cheng explained in a statement. "Meanwhile its perihelion — the closest point on its orbit to the sun — is 44.5 times that of the Earth's orbit, similar to Pluto's orbit."

The outer solar system

We're learning more and more about the outer solar system. Beyond Neptune is the Kuiper Belt; a ring of icy cometary nuclei and planetesimals dominated by Pluto and Charon. The Kuiper Belt begins about 30 astronomical units (AU) from the sun (one AU is the distance of Earth from the sun), its inner edge guarded by Neptune, and extends out to 50 AU. NASA's New Horizons spacecraft is currently exploring the Kuiper Belt.

Meanwhile, the twin Voyager spacecraft have already sped through the Kuiper Belt and have entered a realm called the Scattered Disk, which is thought to go all through way out to more than 1,000 AU and is home to icy bodies on highly elongated and highly inclined orbits. These objects were literally scattered in the region through gravitational interactions with Neptune, and have had their orbits further modified via torques induced by the gravity of passing stars, or the "galactic tide" (the overall gravitational field of the Milky Way galaxy). Beyond the Scattered Disk is the Oort Cloud, which is an immense volume of space that possibly stretches up to a light-year from the sun and is the source of long-period comets.

However, much about the Scattered Disk is still unknown, and besides those long-period comets that venture this way every now and then, no Oort Cloud object has ever been seen — they are too far away and too small. This is why every discovery of a trans-Neptunian object (TNO) on a greatly elongated orbit is vital for piecing together the mystery of the outer solar system.

A new dwarf planet

Around 5,000 TNOs have been discovered until now, but the latest discovery may be one of the most important. Known as 2017 OF₂₀₁, it is currently 90.5 AU away from the sun, but its orbit brings it as close as 4.14 billion miles (6.66 billion kilometers) from our star and as far away as a whopping 157 billion miles (244 billion kilometers). from the sun. For the vast majority of its 24,256-year orbit, 2017 OF₂₀₁ is too far away to be seen with current telescopes; it could only be discovered because its last perihelion came in 1930, and that it's still relatively close.

The object's last perihelion also came, coincidentally, during the same year that Clyde Tombaugh discovered Pluto with a 13-inch (330mm) telescope at Lowell Observatory in Arizona. Would it have been possible for Tombaugh to have also found 2017 OF₂₀₁? Probably not — at magnitude +20.1, this object would have been four magnitudes fainter than Pluto, and it is even fainter today.

Fortunately, telescopic technology has come a long way in the past 95 years, with deep surveys that can capture the passage of a faint object. For example, the Dark Energy Survey (DES) has identified about 800 TNOs — and that's even though DES is ostensibly a cosmological survey. In the same vein, Cheng, along with Jiaxuan Li and Eritas Yang of Princeton University, have been scrutinizing observations made by the Dark Energy Camera Legacy Survey (DECaLS) on the Victor M. Blanco 13-foot (4-meter) telescope at the Cerro Tololo Inter-American Observatory in Chile. They discovered 2017 OF₂₀₁ in archive data going back to 2017 from DECaLS, and also spotted it in old data dating from 2011–12 captured by the 11.7-foot) (3.58-meter) Canada–France–Hawaii Telescope on Mauna Kea.

Based on its brightness and its expected albedo of 0.15 (meaning it would reflect just 15% of the sunlight incident upon it), Cheng's team calculated that 2017 OF₂₀₁ is probably about 435 miles (700 kilometers)) across. This would make it the second largest object found on such an elongated orbit. Although it is substantially smaller than Pluto, which is 1,477 miles (2,377 km) across, 2017 OF₂₀₁ is nevertheless large enough to be classified as a dwarf planet.

Problems for Planet Nine

However, 2017 OF₂₀₁'s existence contradicts the Planet Nine hypothesis, based on our best guess as to Planet Nine's orbit. Planet Nine is a concept that was introduced in 2016 by Caltech astronomers Michael Brown and Konstantin Batygin to explain a perceived clustering of the orbits of many extreme TNOs. The gravity of Planet Nine, which is speculated to be a super-Earth or modest ice giant, would be influencing the orbits of extreme TNOs — or so the hypothesis goes. Yet, the orbit of 2017 OF₂₀₁ is not clustered with the others.

"Many extreme TNOs have orbits that appear to cluster in specific orientations, but 2017 OF₂₀₁ deviates from this," Jiaxuan Li said in the statement.

In our e-mail interview with Cheng, he laid out the repercussions that this could have for the existence of Planet Nine's orbit.

"Planet Nine does allow for extreme TNOs to have unclustered orbits, but those orbits are not stable," he said.

The timescale in which Planet Nine would render 2017 OF₂₀₁'s orbit unstable, and kick it out of the solar system, is in the region of 100 million years. However, the process of placing 2017 OF₂₀₁ in its current orbit, through gravitational interactions with Neptune that pushed 2017 OF₂₀₁ out of the Kuiper Belt — followed by nudges from the galactic tide — takes billions of years. It's possible that 2017 OF₂₀₁ has only recently arrived in its current orbit, which would mean Planet Nine might not have had time to disrupt its orbit yet.

"One important thing is to see if the orbit of our object is stable," Cheng said. "I think, based on analytical criteria, our object is at the boundary between stable and unstable, so further investigation with more comprehensive simulations is needed to definitively rule out the Planet Nine hypothesis."

Intriguingly, 2017 OF₂₀₁ is probably not alone in the outer solar system. It's purely by chance that it happens to be close enough to be detectable — for 99% of its 24,256-year orbit it is too far away to be seen.

"2017 OF₂₀₁ spends only 1% of its orbital time close enough to us to be detectable," said Cheng. "The presence of this single object suggests that there could be another hundred or so other objects with similar orbits and size; they are just too far away to be detectable now.

Just think of that: There could be hundreds of dwarf planets in the outermost reaches of the solar system.

"Even though advances in telescopes have enabled us to explore distant parts of the universe, there is still a great deal to discover about our own solar system," said Cheng.

A pre-print of a paper describing the discovery is available on arXiv.

A surprising chemical difference between Pluto and Sedna, another dwarf planet in the distant Kuiper Belt, is helping scientists nail down their respective masses, a new study reports.

The Kuiper Belt is a region in space beyond the orbit of Neptune that's home to Pluto and most of the known dwarf planets, as well as some comets that are thought to be relics of the solar system's planet-formation era.

"Kuiper Belt objects are icy worlds [that] can tell us what conditions were like billions of years ago," explained study lead author Amelia Bettati, a researcher at Elon University in North Carolina. "Studying them helps scientists understand how planets formed and evolved."

Recent near-infrared spectroscopic studies carried out by the James Webb Space Telescope (JWST) found that Pluto contains both methane and ethane on its surface, key volatile molecules often found in the outer solar system and thought to be remnants from the time when the planets were forming. Sedna, which is less than half as wide as Pluto, was found to have only methane.

Related: What is the Kuiper Belt?

"We hypothesized that the reason for this difference is that Sedna is much smaller than Pluto, so its gravity is weaker," Bettati told Space.com. "This weaker gravity allows methane to escape into space over billions of years, while ethane, which is a heavier compound, stays behind."

While previous studies have identified a general boundary between objects that can hold onto these volatiles and those that cannot, the difference between Pluto and Sedna offers a new clue about how specific escape processes might shape the surface compositions of these distant objects. Sedna, being close to the mass threshold at which volatiles are lost, highlights the importance of understanding how certain chemicals are retained or lost, especially when comparing different Kuiper Belt objects.

"By studying how methane and ethane escape from Sedna, we calculated how massive Sedna must be to explain its current surface composition," said Bettati. "To explain the lack of methane but presence of ethane on Sedna, we must raise the minimum mass estimate for Sedna. This is important because it helps refine our understanding of Sedna's structure and history."

In their study, Bettati and co-author Jonathan Lunine, of NASA's Jet Propulsion Laboratory and the California Institute of Technology, modelled the levels of methane and ethane on Sedna. They verified their model's accuracy using two analogues: Comet 67P/Churyumov-Gerasimenko and Saturn's moon Enceladus.

Europe's Rosetta probe studied Comet 67P up close, and NASA's Cassini spacecraft gathered a wealth of data about Enceladus during the probe's time in the Saturn system.

"Both objects have well-defined measurements and are outer solar system objects, which justifies considering them analogues," said Bettati.

To figure out if enough methane and ethane escaped from these objects to no longer show up in their surface spectra, the scientists needed to estimate how much of these chemicals were originally trapped inside.

They did this under two different scenarios. One assumed that the ratio of methane and ethane to water ice is similar to what was measured on Enceladus, while another looked at the ratio found on Comet 67P during the winter. These comparisons helped them understand how much of these compounds may have been lost over time.

"[We used the] Jeans escape model, [which] is a kind of thermal escape driven by the atmospheric temperature, in which the fastest-moving molecules exceed the escape velocity, but the bulk of the molecules do not," Bettati said.

They also used another model known as hydrodynamic escape, which occurs when the bulk of the molecules are able to escape, rather than just those at the high-velocity end of the distribution. "Much of the atmosphere is in motion, escaping to space," said Bettati.

The models demonstrated that methane has remained stable on Pluto but escaped from Sedna due to its lower mass. Ethane, however, has stayed stable on both objects, even when using two different outgassing rates — 100% (indicating full release of volatiles) and 10% (a smaller release).

This result aligns with the observed surface spectra and provides a more accurate mass estimate for Sedna. The model also explains the absence of methane on another Kuiper Belt object known as Gonggong.

Related: Our solar system map may need an update — the Kuiper belt could be way bigger

"Like Sedna, Gonggong also lacks surface methane," said Bettati. "Since Gonggong is similar in size to Sedna, we believe methane must have escaped from it in a similar fashion. This suggests that smaller Kuiper Belt objects lose methane over time, while larger ones, such as Pluto, can hold onto it.

"If scientists know which gases are likely to be present on different Kuiper Belt objects, their loss rates, and their past compositions, they can better plan future missions."

These findings, in conjunction with JWST observations, will help scientists understand how atmospheres and surface compositions change in the Kuiper Belt and beyond.

"It highlights how JWST is revolutionizing our understanding of the most distant solar system bodies," Bettati said.

The new study was published in February in the journal Icarus.

Using AI to comb through data gathered by NASA's Dawn spacecraft, scientists have conducted a detailed scan of the dwarf planet Ceres to map regions rich in organic molecules to determine whether these "building blocks of life" originated from within the planet or were delivered by external sources.

Ceres boasts a fascinating history. Located in the asteroid belt between Jupiter and Mars, it was once classified as an asteroid. However, its size (Ceres makes up 25% of the asteroid belt's total mass) and distinct characteristics set it apart from its rocky neighbors, leading scientists to reclassify it as a dwarf planet in 2006. Ceres is a cryovolcanic world, where ice and other volatile substances are expelled by volcanic activity instead of molten rock.

It is this volcanic activity that led scientists to previously assume that the organic molecules on the dwarf planet were generated and transported from the dwarf planet's interior, but this new AI-powered study suggests a different explanation. "Of course, the first assumption [was] that Ceres' unique cryovolcanism has transported the organic material from the interior of the body to the surface," said Andreas Nathues from the Max Planck Institute for Solar System Research (MPS) in Germany in a statement. "But our results show otherwise."

Ceres was explored by NASA's Dawn mission, which arrived there in March 2015 and orbited the dwarf planet for about three and a half years. During this time, the spacecraft's scientific camera and onboard spectrometer mapped its entire surface.

At the time, scientists identified potential patches of organic material by observing that the amount of light reflected from certain areas on Ceres' surface was higher in longer wavelengths. Organic materials, especially those with complex molecules like hydrocarbons, often reflect more light from longer wavelengths due to their molecular structure, which influences how they absorb and scatter light.

Based on their initial analysis, researchers believed that the deposits they identified could contain organic compounds with a chain-like structure, known as aliphatic hydrocarbons. However, their remote data couldn't pinpoint the exact types of molecules with any certainty.

Now, using AI, scientists have reanalyzed the entire surface of the dwarf planet Ceres. While previous studies identified organic compounds in specific regions, AI allowed for a systematic examination of the Dawn mission's full dataset, uncovering patterns that had previously been overlooked.

By cross-referencing spectral data with geological features, AI helped the team confirm that organic materials were in fact not associated with sites of cryovolcanic activity. "Sites of such organic molecules are actually rare on Ceres, and devoid of any cryovolcanic signatures," commented one of the study's scientists, Ranjan Sarkar from MPS, in the statement.

These findings help rule out the possibility that the organic molecules originated from Ceres' interior. Conversely, where organic compounds were reliably detected, there were no signs of deep or surface activity.

"At none of the deposits do we find evidence of current or past volcanic or tectonic activity: no trenches, canyons, volcanic domes or vents. Furthermore, there are no deep impact craters nearby," said Martin Hoffmann, also from MPS.

The vast majority of deposits were located along Ceres' large Ernutet crater in its northern hemisphere. Only three are located at a greater distance from it. Two patches were not previously known.

"Unfortunately, Dawn can't detect all types of organic compounds," said Nathues. "However, the organic deposits that have been reliably detected with Dawn so far likely do not originate [from] Ceres itself."

One plausible explanation researchers propose is that organic material was delivered to Ceres by the impact of one or more asteroids from the outer asteroid belt — a theory supported by computer simulations. These simulations show that such asteroids frequently collide with Ceres, but because they originate from the same general region, their relative velocities are low. As a result, the impacts generate little heat, allowing organic compounds to survive without being destroyed.

This is significant, as it suggests that organic molecules could have been present on asteroids and comets in the outer solar system early in its formation and may have only reached the inner solar system much later, potentially playing a key role in the development of life here on Earth.

A brand-new group of frozen objects, orbiting the sun out beyond the distant Kuiper Belt, has been spotted by the Subaru telescope, working with NASA's New Horizons mission to find new targets for the spacecraft to investigate.

"If this is confirmed, it would be a major discovery," said Fumi Yoshida, from the University of Occupational and Environmental Health Sciences and the Planetary Exploration Research Center, Chiba Institute of Technology, in a statement.

Subaru, which is an 8-meter (26-foot) telescope atop Mauna Kea in Hawaii, has been working with New Horizons since its 2006 launch toward Pluto, which the spacecraft flew by in 2015. Since then, New Horizons has been blazing a trail through the Kuiper Belt, which is a ring-shaped region of icy cometary bodies beyond the orbit of Neptune at distances between 33 and 55 astronomical units (AU). An astronomical unit is equivalent to Earth's average distance from the sun, which is 149.6 million kilometers (93 million miles). 

When Subaru began searching for Kuiper Belt objects in 2004 as potential targets for New Horizons to either visit up close or to watch with its cameras from a distance after encountering Pluto, the telescope was faced with a problem. At the time, Pluto and the area of the outer solar system to which New Horizons was headed was in the constellation of Sagittarius, which has the dense center of the Milky Way as a backdrop, making it hard to pick out Kuiper Belt objects from all the background stars. At the time, Subaru identified just 24 Kuiper Belt objects, all of which were too far away for New Horizons to reach or view with its cameras after leaving Pluto. (Arrokoth, a Kuiper Belt object that New Horizons visited on New Years' Day 2019, was found by the Hubble Space Telescope.)

Related: What is the Kuiper Belt?

Now, however, Pluto and that part of the solar system has moved away from the backdrop of the Milky Way into a sparser region of the night sky. With its Hyper Suprime-Cam (HSC), Subaru has discovered 239 Kuiper Belt objects since 2020. Most of these are regular Kuiper Belt objects, but a smattering seem to be very special indeed.

"The most exciting part of the HSC was the discovery of 11 objects at distances beyond the known Kuiper Belt," said Yoshida.

This new group of objects isn't a mere extension of the Kuiper Belt. There appears to be a gap between 55 AU and 70 AU where no objects have yet been found, and then a second belt — let's call it "Kuiper Belt 2" — between 70 and 90 AU, which is as far out as 13.5 billion kilometers (8.4 billion miles) from the sun. For comparison, Neptune lies at 30 AU and New Horizons is currently 60 AU from the sun, while NASA's Voyager 1 and Voyager 2 probes are 164.7 and 137.6 AU from the sun, respectively — out in interstellar space.

Related: Solar system planets, order and formation: The ultimate guide

The architecture of the solar system, including the asteroid belt and the Kuiper Belt, was determined by the processes that formed the planets, including how the young Jupiter migrated through the system, scattering smaller bodies far and wide.

"I think the discovery of distant objects and the determination of their orbital distribution are important as a stepping stone to understanding the formation history of the solar system, comparing it with exoplanetary systems, and understanding universal planet formation," said Yoshida.

The discovery of this new population of bodies is not entirely out of the blue. The Student Dust Counter instrument on board New Horizons keeps detecting impacts from dust particles, though the rate of impacts should be decreasing as New Horizons departs the Kuiper Belt. The continued presence of dust suggests that it is being produced by a population of bodies farther out. In addition, New Horizons has witnessed unexplained stellar occultations — when an object passes in front of and briefly blocks the light of a distant star — that could be the product of objects in this newly discovered, more distant 'Kuiper Belt 2.'

Furthermore, observations of protoplanetary disks around other stars, such as those seen by ALMA, the Atacama Large Millimeter/submillimeter Array in Chile, clearly show extended regions and numerous belts and gaps in the region beyond where the Kuiper Belt is in our solar system.

"Our solar system's Kuiper Belt long appeared to be very small in comparison with many other planetary systems, but our results suggest that idea might just have arisen due to an observational bias," said Wes Fraser of the National Research Council of Canada, who led the new findings. "So maybe, if this result is confirmed, our Kuiper Belt isn't all that small and unusual after all compared to those around other stars."

Because the Kuiper Belt had seemed small, one theory had been that the solar nebula that formed our planetary system had also been smaller than normal. The discovery of this Kuiper Belt 2 suggests that was not necessarily the case.

"The primordial solar nebula was much larger than previously thought, and this may have implications for studying the planet formation process in our solar system," said Yoshida.

Astronomers will continue to use Subaru to track the 11 objects in this new belt to better define their orbits. Given they were found in a small region of space, they probably are only the tip of the iceberg and hint at a much larger population. Their discovery is further evidence that there is still much to be discovered in the extreme depths of the outer solar system, including the possibility of more dwarf planets and even the hypothesized Planet Nine.

"This is a groundbreaking discovery revealing something unexpected, new and exciting in the distant reaches of the solar system," said Alan Stern, who is the principal investigator on the New Horizons mission. "This discovery probably would not have been possible without the world-class capabilities of the Subaru Observatory."

The findings are set to be published in the Planetary Science Journal, and are currently available as a preprint.  

Pluto may have lost its status as a full-fledged planet in 2006, but that doesn't mean it's a joke of a world this April Fools' Day and the folks behind Pluto TV want to make that clear. 

On April 1, the free Pluto TV streaming service will host a "sit-in" to revisit the Pluto planethood debate while also celebrating the 10th anniversary of the live TV streaming service. The event, dubbed "Pluto TV's Rally for Pluto! Make Pluto A Planet!," runs from 11:30 a.m. to 1 p.m. Pacific Time at the University of California Los Angeles' Bruin Plaza. 

You can follow along live online via Pluto TV's Instagram, X (formerly Twitter), Facebook, Threads and TikTok channels. And if you can't make it in person, you can sign a Change.org petition for Pluto's planethood to make your voice heard.

Related: Why is Pluto not a planet?

"Join the citizens of Pluto for a rally to spark the conversation around Pluto's planetary status," Pluto TV said in a statement. "It's been 18 years since Pluto was demoted and we think it's time for Pluto to have a vote in its own destiny. "

Pluto TV has enlisted Pluto pioneer Alan Stern, principal investigator for NASA's New Horizons mission (which made the first Pluto flyby in 2015) to speak on Pluto's behalf. Space.com has confirmed with Stern that's it's no April Fools prank. He actually will speak at the event. 

A video message from astrophysicist Neil DeGrasse Tyson, director of the Hayden Planetarium at the American Museum of Natural History in New York City, who supported Pluto's demotion, is also expected to be played at the rally during the debate. Tyson recently launched his StarTalk TV streaming channel on Pluto TV.

Related: What is a planet?

Pluto is currently classified as a dwarf planet after losing its planethood status in 2006 during a vote by astronomers with the International Astronomical Union. The vote came amid a larger debate over what makes a planet, and if being round with moons (like Pluto is - it has five moons) is enough to qualify. Ultimately, scientists opted to demote Pluto to a dwarf planet rather than raise other dwarf planets in our solar system (like Ceres, the largest asteroid in the asteroid belt) up to planetary status. 

Since then, Pluto supporters and naysayers have been vocal about the decision, but that hasn't stopped true Pluto planet lovers from continuing their fight for its status. 

Pluto TV's Pluto rally aims to both celebrate the streaming service's 10th birthday while supporting what it calls a planetary underdog.

"The sit-in will feature high-profile guest speakers, fun chants, snacks and more all in the name of scientific fun!" Pluto TV event organizers wrote. "If you’re a believer in Pluto’s right to planet-hood, sign the petition online to show your support."

Close to 18 years ago, astronomers spotted a miniature, icy world named Eris billions of miles beyond Neptune. But unlike its dwarf planet cousin Pluto — which New Horizons promoted to a rich, dynamic world after its visit in 2015 — Eris has not had any robotic visitors. It is so far away from Earth, in fact, that it shows up in observations just as a single pixel of light. 

All in all, scientists know very little about what happens on Eris.

Though what we do know is Eris is known to have an atmosphere that freezes and snows onto the surface below, thanks to its place near the edge of the solar system. It's about 68 times farther from the sun than Earth is. And now, new models based on data from an array of radio telescopes in Chile have revealed more about Eris. Heat leftover from the dwarf planet's birth seems to be oozing out and slowly flexing its icy surface.

Related: Dwarf Planet Eris is 'Almost Perfect' Pluto Twin

The process is causing Eris to behave less like a solid, rocky planet and "more like a soft cheese or something like that," study co-author Francis Nimmo of the University of California Santa Cruz said in a statement. "It has a tendency to flow a bit."

While a lot still remains unknown about Eris, it is considered an "almost perfect" twin of Pluto — both dwarf planets are nearly exactly the same size. Actually, when it was first spotted in 2005, it appeared to be slightly bigger than Pluto, triggering a debate among scientists. This had led the International Astronomical Union (IAU) to clarify its definition of a planet and demote Pluto to a dwarf planet. It was thanks to this contention in the scientific community that the IAU in 2006 named the dwarf planet Eris, after the Greek goddess of discord.

For the latest study, Nimmo and his colleague Mike Brown, a Caltech astronomer who had led the discovery of Eris in 2005 and is best known as the man who killed Pluto, estimated the mass for Eris' very small moon Dysnomia. Eris and its satellite are mutually tidally locked, which means both face the same way toward each other. Scientists think this is because the tiny moon "raises" tides on Eris, causing the dwarf planet to spin down over 4.5 billion years.

The new findings show Eris likely has a rocky core enveloped by a convecting icy shell. 

"The rock contains radioactive elements, and those produce heat. And then that heat has to get out somehow," said Nimmo. "So as the heat escapes, it drives this slow churning in the ice."

He and Brown suspect the surface of Eris should be "pretty smooth" as any surface features will likely be erased by flowing ice. 

"So it would be nice to get some measurements of what shape Eris is because if it's very irregular, that would not agree with our model."

This research is described in a paper published Nov. 15 in the journal Science Advances. 

Numerous asteroids that have punctured the surface of dwarf planet Ceres also appear to have influenced its reservoir of precious organic molecules.

In 2017, scientists studying data sent home by NASA's Dawn spacecraft initially spotted organic compounds known as aliphatic molecules near a 32-mile-wide impact crater on Ceres. Since then, they have been trying to pin down the origin of these molecules; few studies suggested asteroids delivered them to the dwarf planet while others concluded they were formed on Ceres itself.

"We are finding that organics may be more widespread than first reported and that they seem to be resilient to impacts with Ceres-like conditions," Juan Rizos, an astrophysicist at the Instituto de Astrofisica de Andalucia in Spain and a co-author of the new study, said in a statement.

Related: Astronomers spy new class of dark, water-rich asteroids like dwarf planet Ceres

To arrive at their conclusions, Rizos and his colleagues carried out a series of experiments mimicking the impact conditions expected on Ceres at NASA's Ames Vertical Gun Range in California, a facility dedicated to simulating the physics and mechanics of impact cratering and asteroid strikes. The team also merged data from the camera and imaging spectrometer on Dawn, and the two datasets together allowed the team to map organic-rich areas on Ceres in greater detail than previously done. 

The findings collectively show a "good correlation" of organics with areas hosting older impacts, researchers say, showing that asteroid strikes did indeed influence the presence and abundance of organics across billions of years.

"While the origin of the organics remains poorly understood, we now have good evidence that they formed in Ceres and likely in the presence of water. There is a possibility that a large interior reservoir of organics may be found inside Ceres," Rizos said in the same statement. "So, from my perspective, that result increases the astrobiological potential of Ceres."

The 2023-2032 decadal survey for planetary science and astrobiology earmarked Ceres as a high priority target for a sample return mission, which might occur several decades into the future. 

In the meantime, another NASA probe called Lucy will soon explore 10 trojan asteroids thought to hold clues to the creation of our solar system and even Earth, thanks to hosting material from the early solar system. 

"We will likely find differences, as the Trojan asteroids have experienced very different impact histories from Ceres," said Rizos, "and because there are two compositionally different types of Trojan asteroids." Comparing data from the Lucy mission to that gathered by Dawn will help us better understand how these organic molecules are sprinkled throughout the outer solar system, she added.

This research was presented Tuesday (Oct. 17) at the Geological Society of America's GSA Connects 2023 meeting. 

If you've never heard of the dwarf planet Haumea, tonight's a pretty good night to become familiar with the football-shaped celestial body. 

Located in the Kuiper Belt beyond Neptune, this frigid dwarf planet reaches both opposition (the point directly opposite the sun from the perspective of Earth) and perigee (the point in its orbit closest to Earth) tonight. And it'll be visible in the night sky in the constellation Boötes.

From New York City, per In-the-Sky.org, Haumea will become visible in the night sky at 8:49 p.m. EDT (0049 GMT on April 21) and will remain so until dawn, when the sun's light will overpower the dwarf planet. Look to the east some 24 degrees above the horizon, which will correspond to just over two widths of your fist held at arm's length.

Related: NASA seeks origin of 'weird' fast-spinning dwarf planet Haumea

Haumea was first spotted by two different groups of astronomers looking at observations made between 2003 and 2004, earning it the name 2003 EL61. Until 2008, it was classified as a Kuiper Belt Object (KBO) — a reclassification by the International Astronomical Union deemed it a dwarf planet, joining, Pluto, Eris, and Makemake in the Kuiper Belt and Ceres in the asteroid belt. At that time, it was given the name Haumea after the Hawaiian goddess of fertility.

The dwarf planet, which is roughly the size of Pluto, takes about 285 years to orbit the sun, and its distance from Earth varies from 34 to 51 astronomical units, or AU (one AU is the distance between the Earth and the Sun). As it's reaching perigee, that puts it at a distance of 34 AU tonight.

Though its orbit might be quite slow, Haumea rotates extremely fast — it takes just four hours to complete one rotation. Because of the centrifugal force it experiences due to this rotational speed, Haumea is stretched out like a football instead of round like most other planets and dwarf planets. Haumea is also the only known dwarf planet to have rings, and it also has two small moons, Namaka and Hi'iaka, which are the daughters of Haumea in Hawaiian mythology.

If you'd like to get a closer look at Haumea, dive into our guides to the best telescopes and best binoculars. And if you'd like to photograph the night sky while you're stargazing, our guides to the best cameras for astrophotography and best lenses for astrophotography might be helpful.

Editor's Note: If you take an image of Haumea at opposition and would like to share it with Space.com's readers, send your photo(s), comments, and your name and location to spacephotos@space.com.

Follow Stefanie Waldek on Twitter @StefanieWaldek. Follow us on Twitter @Spacedotcom and on Facebook. 

As the moon reaches its new phase on Tuesday (March 21), the dwarf planet Ceres will lie opposite the sun in Earth's sky, in an arrangement astronomers call "opposition." 

Ceres will be visible for most of the night with no moonlight to drown it out, but don't expect mind-bending views: The dwarf planet will be a star-like point of light, even through a telescope, according to In the Sky.

Located in the main asteroid belt between Mars and Jupiter, the dwarf planet officially known as 1 Ceres will be in the constellation of Coma Berenices. While in opposition, Ceres will also be in perigee — its closest approach to Earth during its orbit around the sun — meaning the dwarf planet will be at its brightest. 

Related: March 2023 skywatching guide

From New York City, In the Sky added, Ceres will become observable from around 8:35 p.m. EDT (0035 GMT on March 22) when it will rise to 21 degrees over the horizon to the east. Ceres will reach its highest altitude at around 1:31 a.m. EDT (0531 GMT) on March 22, when it will be 64 degrees over the horizon to the south. Ceres will disappear when the sun's light washes it out at around 5:51 a.m. EDT (0951 GMT) as it sits at around 28 degrees over the horizon to the west. (For perspective, your clenched fist held at arm's length spans about 10 degrees of sky.)

During the close approach, Ceres will still be around 147 million miles (237 million kilometers) from Earth. It will reach a peak brightness magnitude of around 6.9, meaning that, even through a telescope, it will appear as no more than a point of light. 

Ceres is the largest object in the main asteroid belt and has the distinction of being the only dwarf planet in the inner solar system. Most of these objects are located in the Kuiper Belt, a band of icy bodies out beyond the orbit of Neptune.

Spotted in 1801 by Giuseppe Piazzi, Ceres was initially believed to be an asteroid but was eventually found to be much larger than other bodies in the asteroid belt, receiving its dwarf planet designation in 2006.

Though Ceres comprises a quarter of the mass of the entire asteroid belt, the solar system's most famous dwarf planet Pluto is still 14 times more massive than Ceres, which is just 592 miles (953 km) wide. If Earth were the size of a nickel, NASA said, Ceres would be no larger than a poppy seed.  

In 2015, Ceres, which takes 4.6 Earth years to orbit the sun, became the first dwarf planet to be visited by a spacecraft. NASA's Dawn mission studied Ceres from orbit from 2015 to 2018, after circling another of the asteroid belt's largest objects, Vesta. 

Though Ceres lacks an atmosphere and a magnetosphere, planetary scientists are keen to explore it, as it may be composed of around 25% water, a key ingredient for life. 

If you're hoping to catch a look at the new moon or Ceres during the dwarf planet's opposition and close approach, our guides to the best telescopes and best binoculars are a great place to start. If you're looking to snap photos of the night sky in general, check out our guide on how to photograph the moon, as well as our best cameras for astrophotography and best lenses for astrophotography.

Editor's Note: If you snap Ceres or the new moon and would like to share it with Space.com's readers, send your photo(s), comments, and your name and location to spacephotos@space.com.

Follow us on Twitter @Spacedotcom or on Facebook. 

Astronomers are slowly shining light on the dark objects hovering in a narrow part of the asteroid belt between Mars and Jupiter.

In a new study, researchers found that 10 well-known asteroids have features much like the belt’s largest object, the dwarf planet Ceres, including minerals on their surfaces that formed through reactions with liquid water. They estimate these Ceres-like asteroids formed just 1.5 million to 3.5 million years after our solar system's birth, which makes them important remnants of complex chemical and physical processes that occurred in the early solar nebula.

"These asteroids are almost as old as our solar system," Driss Takir, a planetary scientist at NASA's Astromaterials Research and Exploration Science and the study's lead author, told Space.com in an email.

Related: Facts and information about the asteroid belt

The newly studied objects belong to a family of dark asteroids that's one of the oldest in the asteroid belt. Their reflectivity, or albedo, is less than 0.09, and their diameters are more than 62 miles (100 kilometers). Over 200 such objects are known to exist in the asteroid belt, so the ongoing research will likely reveal more Ceres-like asteroids, Takir noted. 

The current group includes 24 Themis, the first nearby asteroid to sport signs of water ice on its surface, and 65 Cybele, which came in second. Although their history and spectral features are similar to that of Ceres — whose interior has revealed hints of organic material — researchers do not yet know why most of them are located at or beyond 3 astronomical units (AU) or 278,867,421 miles (448,793,610 km), which is outside of Ceres' orbit. (One AU is the average Earth-sun distance — about 93 million miles, or 150 million km.)

Takir's team used NASA’s Infrared Telescope Facility telescope in Hawaii to study the 10 asteroids in near-infrared wavelengths. They employed an observational technique called near-infrared reflectance spectroscopy, which allowed them to calculate how much sunlight reflected from the surfaces of asteroids. In turn, this helped researchers study the mineral and chemical compositions of the surfaces, which are unlike "any meteorite in our terrestrial meteorite collections," Takir told Space.com.

This could be because volatile-rich materials ejected from asteroids' surfaces do not tend to survive the journey through Earth's atmosphere, Takir noted. The closest category researchers found for the latest asteroid group is that of Ceres — the carbonaceous chondrite class.

Takir’s team also found that these Ceres-like asteroids are highly porous, thanks to low temperatures far from the sun that have prevented them from morphing into compact rock-like structures.

"They maintained the porous and primitive character typical of the outer ice planets located far from the sun," Wladimir Neumann, a co-author of the study, said in a statement.

To better understand how these dark asteroids came to be at their current home in the outer reaches of the asteroid belt, researchers used computer models to trace their evolution. They found that these asteroids likely formed farther out in the solar system and were pulled into their current home by Jupiter's or Saturn's gravity. 

Next, researchers plan to explore if there are any more Ceres-like large asteroids in the main belt. They say high-resolution and high-sensitivity instruments onboard the James Webb Space Telescope (JWST) will help them better characterize the mineralogy and composition of these asteroids. 

Also of interest is a possible sample-return mission to Ceres to retrieve a sample of evaporites evolved from deep brines, Takir told Space.com. Such a mission is recommended in the 2023-2032 NASA Planetary Science Decadal Survey.

The research is described in a paper published (Feb. 20) in the journal Nature Astronomy.

Follow Sharmila Kuthunur on Twitter @Sharmilakg. Follow us on Twitter @Spacedotcom or on Facebook. 

A mini-planet orbiting in the frigid outer reaches of the solar system has a Saturn-like ring of dust and debris that defies the rules of physics, a new study has revealed. 

The planet in question is called Quaoar and it's the seventh largest of the known dwarf planets of which Pluto is the king. Discovered in 2002 and about 697 miles wide (1,121 kilometers), Quaoar is one of the so-called trans-Neptunian objects, small planets orbiting beyond the solar system's outermost planet Neptune. 

Residing in the Kuiper Belt, the doughnut-shaped ring of rocky and icy debris in the outer solar system, Quaoar is a proud owner of its own moon, the 100-mile-wide (160 km) Weywot. And a recent observation campaign revealed that it also has a ring of material in its orbit. 

That by itself wouldn't be so special. The gas giant Saturn is known to possess a whole series of rings. Jupiter, Neptune and Uranus also have some. One other trans-Neptunian object — Haumea — has been found to have a ring, and the space rock Chariklo that orbits between Saturn and Uranus also has one. So what exactly sets Quaoar's ring apart? 

Related: Dwarf planets: science & facts about the solar system’s smaller worlds

Quaoar's ring is at a very unusual distance from its parent body. In fact, before astronomers discovered Quaoar's ring in observations from several telescopes conducted between 2018 and 2021, they had thought that it was impossible for a ring to exist at such a distance. With a radius of about 2,420 miles (3,885 km) from Quaoar's center, the ring is too far away from the dwarf planet that its gravity should no longer be able to keep the material dispersed. Instead, it should coalesce under its own gravity and form another moon, just like Weywot. By not having done that, the ring has breached what astronomers call the Roche limit, the first known ring around a celestial body to have done so. 

"What is so intriguing about this discovery around Quaoar is that the ring of material is much farther out than the Roche limit," Giovanni Bruno, an astronomer at Italy's National Institute for Astrophysics (INAF) and one of the authors of the paper, said in a European Space Agency (ESA) statement. "As a result of our observations, the classical notion that dense rings survive only inside the Roche limit of a planetary body must be thoroughly revised."

The ring was discovered during a series of occultations, essentially eclipses, when Quaoar passed between Earth and several more distant but much brighter stars. When an occultation occurs, the light of the background star temporarily dims. The effect is only visible to very sensitive telescopes and is frequently used to detect exoplanets orbiting stars in our Milky Way galaxy, which is why ESA's exoplanet hunter Cheops was among the telescopes watching these Quaoar occultations. 

When astronomers analyzed the data, they realized that apart from the main dip in the background stars' brightness, they could detect two smaller drops. Since drops occurred before and after the main occultation, respectively, the researchers thought that Quaoar must be surrounded with a ring. 

Several Earth-based telescopes also observed the occultations with similar results, but Cheops' data were particularly valuable as they proved that the odd dimmings were not caused by the effects of Earth's atmosphere.

"The Cheops data are amazing for signal to noise," Isabella Pagano, also of INAF and a member of the Cheops Board, said in the statement. "The signal to noise is a measure of how strong the detected signal is to the random noise in the system. Cheops gives a great signal to noise because the telescope is not looking through the distorting effects of Earth’s lower atmosphere."

Now astronomers have to either rethink the Roche limit or come up with another explanation for the existence of Quaoar's ring. 

The study was published on Wednesday (Feb. 8) in the journal Nature. 

Follow Tereza Pultarova on Twitter @TerezaPultarova. Follow us on Twitter @Spacedotcom and on Facebook. 

The origins of a dwarf planet that lurks at the outer edge of the solar system that has become one of its strangest objects may have been revealed by NASA scientists.

Haumea is around the size of fellow dwarf planet Pluto and is located in the Kuiper belt, a collection of icy debris and cometary bodies out past the orbit of Neptune — the solar system's outermost planet.

Haumea is notable because it spins faster than any other solar system object of a similar size, completing a rotation around its axis — or a 'day' — in just four hours. 

This rapid spin has resulted in Haumea developing a shape that resembles a deflated football rather than a sphere. Its shape isn't the only unusual thing about this dwarf planet, however. 

A strange ice mystery

Haumea also has a surface that is mostly made of a kind of water ice unlike most of the other bodies in the Kuiper Belt. 

This water-ice surface is shared by some of Haumea's siblings that also appear to share the same orbit as the dwarf planet. This has led scientists to conclude Haumea and these icy bodies share the same origin and that they form the only ‘family’ of related objects found in the Kuiper Belt — the 'Haumean family.'

Using computer simulations, NASA scientists including Goddard Space Flight Center in Greenbelt, Maryland, post-doctoral student Jessica Noviello investigated the question "How did something as weird as Haumea and its family come to be?"

Computer simulations are necessary to achieve this due to the fact the dwarf planet is too far away to measure precisely using an Earth-based telescope, and Haumea is yet to be visited by a space mission.

These simulations allowed the team to 'take apart' Haumea and then rebuild it from scratch. The aim of this was to understand the chemical and physical processes that shaped the dwarf planet. 

"To explain what happened to Haumea forces us to put time limits on all these things that happened when the solar system was forming, so it starts to connect everything across the solar system," team member and Arizona State University in Tempe, professor of astrophysics, Steve Desch said in a statement. "There are a lot of odd, 'gee whiz' parts to Haumea, and trying to explain them all at once has been a challenge."

The model developed by the team started with the input of just three pieces of data about Haumea; its estimated size, its estimated mass, and its short four-hour-long "day."

This delivered a revised prediction of the dwarf planet's size and mass, and its density. It also delivered a prediction of Haumea's core size and density. 

Using this information Noviello was able to determine how the dwarf planet's mass is distributed and how that distribution has influenced its spin. From here the researcher set about simulating billions of years of evolution for Haumea searching for the right set of features that would result in the dwarf planet astronomers observe today.

"We wanted to understand Haumea fundamentally before poking back in time," Noviello said. 

 Haumea family values 

The team made the assumption that the infant Haumea was around 3% larger than its current size with this difference accounting for the creation of its Kuiper belt siblings. 

The scientists also assumed the young dwarf planet rotated at a different speed and that its volume was larger than it is today. 

Altering the features of Haumea in the models they developed allowed the team to run dozens of simulations viewing how small changes like increasing or decreasing the size of the dwarf planet changed its evolution. 

Arriving at a model that delivered a simulated Haumea just like astronomers observe today told the team they had hit on the right early features and the current evolutionary path for the Kuiper belt dwarf planet. 

Noviello and her colleagues' modeling revealed that in its early years and during an epoch of the solar system that was marked by chaotic conditions Haumea collided with another body in a powerful impact.

This resulted in pieces breaking away from young Haumea, but these fragments didn't go on to become the Haumean family objects. This is because such a large impact would have knocked the pieces into far more scattered orbits than that possessed by the Haumean family bodies. 

Desch said the objects that comprise the Haumean family likely would have actually formed later in the dwarf planet's existence as its structure was developing. In this later period of its evolution dense, rocky material was sinking to the dwarf planet’s center while lighter-density ice was rising to its surface. 

"When you concentrate all the mass towards the axis, it decreases the moment of inertia, so Haumea ended up spinning even faster than it does today," Desch said. This would result in rotational speeds fast enough to throw off surface ice which went on to become the Haumean family.

This moment of inertia would have further increased, decreasing the dwarf planet's rate of spin as a result of radioactivity from the rocks of the Haumea melting surface ice. This water soaked to the center of the dwarf planet caused rocky material there to swell to a large but less dense clay core.

The team's research was published in the Planetary Science Journal on Sept. 29.

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Plutonium is radioactive, but it doesn't seem that harmful at first glance. It looks like any other metal, with a silvery sheen that turns dull in contact with the air. Queen Elizabeth II held a piece during a visit to Britain's Atomic Energy Research facility at Harwell in 1957. It was warm to the touch, but it didn't hurt. 

According to the World Nuclear Association, even eating it doesn't really do any harm, although it's definitely not recommended.

Plutonium atoms fall apart through a process called alpha decay. They release particles made from two neutrons and two protons (essentially a helium nucleus). They're so bulky that they can't pass through human skin. Left to its own devices, plutonium decays slowly. The real danger comes when humans interfere. 

Related: What is the Standard Model?

An isotope of plutonium named plutonium-239 is fissile, which means that it can start a nuclear chain reaction. The United Nations lists it as one of only two radioactive isotopes used to make atomic bombs. When you hit a plutonium-239 atom with a neutron, more neutrons will spill out. When those neutrons hit other plutonium-239 atoms, the same thing happens again. And again. This releases an enormous amount of energy.

Under the right conditions, the energy from nuclear fission can be harnessed for good. The heat released can boil water, which can make steam, which can spin turbines. According to the World Nuclear Association, a third of the energy made by nuclear power plants comes from plutonium. 

But it can also be used as a weapon. In 1945, the United States developed a bomb containing a small sphere of plutonium and then used it to devastate the Japanese city of Nagasaki.

Where does plutonium come from?

The International Panel on Fissile Materials estimates that there are now 140 tons of weapons-grade plutonium worldwide. It forms part of the so-called 'nuclear deterrent' in countries like the USA, the UK, and Russia. 

According to the National Nuclear Security Administration, you only need a bowling-ball-sized amount of plutonium to make a pit, the core of an atom bomb. But, getting hold of the raw materials isn't easy. 

Plutonium doesn't really exist in nature; it only comes from nuclear reactors. The International Atomic Energy Agency says that there's one place in Africa, called Oklo, where the conditions were just right to create the element naturally. But most plutonium is completely human-made. 

Plutonium power

A radioisotope thermoelectric generator, RTG for short, is a nuclear battery. It captures the heat from decaying plutonium and turns it into electricity using wires called thermocouples. When one end of a thermocouple gets hot, a current starts to flow.

RTGs are used to bring power to the remotest of places, from lighthouses on hazardous coastlines to probes in outer space. But you can't use any old radioactive element to make them.

NASA has a strict list of criteria for nuclear batteries. The fuel must be safe, in case of a launch accident. It mustn't release too much beta, gamma, or neutron radiation, because they interfere with equipment. It must be stable because you don't want it to explode. It must have a long half-life because you can't change a battery in space. And it must be light because it needs to get off the launch pad. 

The World Nuclear Association says that, of the 2,900 known radioactive isotopes, plutonium-238 is one of just 22 suitable for the job.

The discovery of plutonium

Plutonium is a relatively new addition to the periodic table. 

According to the Los Alamos National Laboratory, scientists first encountered it during World War Two. In 1940, scientists at the Berkeley Radiation Laboratory were experimenting with uranium, firing heavy hydrogen atoms at the element to see what would happen. 

Uranium is radioactive, and the bombardment caused it to split apart, releasing another radioactive element, neptunium. That element was unstable, and it decayed into yet another, unknown radioactive element. Following the planetary theme, the scientists called it plutonium. Its potential as a nuclear weapon was immediately evident and within two years top-secret production had started at the Metallurgical Laboratory in Chicago. 

Plutonium uses

Nuclear weapons

According to the Royal Society of Chemistry, a kilogram of plutonium can produce a blast equivalent to 10,000 tonnes of chemical explosives. Nuclear treaties aim to prevent the use of these devastating weapons.

Space heaters

The electrical components on spacecraft operate best at certain temperatures. Plutonium-238 releases a lot of heat when it decays, helping to warm these delicate instruments in deep space.

Thermal energy

The heat generated by decaying plutonium can be captured and turned into electricity. According to the World Nuclear Association, one kilogram of plutonium can make 8 million kilowatt hours of electricity.

Nuclear pacemakers

A handful of people in the United States have plutonium-powered pacemakers. These devices are not dangerous inside the body, but the Los Alamos National Laboratory disposes of them carefully when they're removed.

Additional resources

To learn more about the details of Plutonium, you can visit the Royal Society of Chemistry website. Additionally, to find out about the use of Plutonium-238 for space exploration, read this article from the American Chemical Society.

Bibliography

"The drama of plutonium". Nuclear Engineering International (2005).

"Plutonium". World Nuclear Association (2021). 

"Alpha decay". Atomic Archive (2022). 

"Fissile material". The United Nations.

"Fissile material stocks". International Panel on Fissile Materials (2022). 

"Plutonium Pit Production". National Nuclear Security Administration (2022). 

"Meet Oklo, the Earth's Two-billion-year-old only Known Natural Nuclear Reactor". International Atomic Energy Agency (IAEA) (2018). 

"Thermocouple sensor". OMEGA (2022). 

"About Plutonium-238". NASA Radioisotope Power Systems.

"Atomic number 94". Los Alamos National Laboratory (2021).

"Metallurgical Laboratory at the University of Chicago". Office of Legacy Management. 

Strange hexagonal diamonds may have been jettisoned into space when a dwarf planet collided with a large asteroid around 4.5 billion years ago. 

New research identified the hexagonal diamonds, also called lonsdaleite,  in a rare class of meteorites that might come from the mantle of a dwarf planet. Like graphite, charcoal and diamond, lonsdaleite is a particular structural form of carbon. Where diamond's carbon atoms are arranged in a cubic shape, the carbon atoms in lonsdaleite are arranged in hexagons.

"This study proves categorically that lonsdaleite exists in nature," Dougal McCulloch, a microscopist at RMIT University in Australia, said in a statement. "We have also discovered the largest lonsdaleite crystals known to date that are up to a micron in size  —  much, much thinner than a human hair."

Related: How many meteorites hit Earth every year?

Lonsdaleite was first discovered in the Canyon Diablo meteorite in 1967 and was named after British crystallographer Dame Kathleen Lonsdale. The new research predicts that the hexagonal shape of lonsdaleite makes it harder than regular diamonds with a cubic structure, which might pen new manufacturing techniques to make ultra-hard materials.

The researchers studied lonsdaleite in ureilite meteorites, a rare class of space rocks that scientists think may contain material from the mantle of dwarf planets. The team analyzed slices of these meteorites under the microscope to identify the lonsdaleite and predict its origins, and also studied regularly shaped diamonds found in the rock. 

"There's strong evidence that there's a newly discovered formation process for the lonsdaleite and regular diamond, which is like a supercritical chemical vapor deposition process that has taken place in these space rocks, probably in the dwarf planet shortly after a catastrophic collision," McCulloch said. "Chemical vapor deposition is one of the ways that people make diamonds in the lab, essentially by growing them in a specialized chamber."

The scientists think that lonsdaleite in the meteorites formed from a supercritical liquid at high temperatures and under increased pressures. This extreme environment allowed the lonsdaleite to retain the shape and texture of graphite. Eventually, as the environment cooled and the pressure reduced lonsdaleite was partially replaced by diamond. 

The team thinks that industry could mimic the process to produce the unusual mineral.

"Nature has thus provided us with a process to try and replicate in industry," Andy Tomkins, team leader and a geologist at Monash University in Australia, said in the same statement. "We think that lonsdaleite could be used to make tiny, ultra-hard machine parts if we can develop an industrial process that promotes the replacement of pre-shaped graphite parts by lonsdaleite."

The team's research was published Monday (Sept. 12) in the Proceedings of the National Academy of Sciences.

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Radioactive matter within the dwarf planet Ceres may help drive geological activity there, a new study finds.

With a diameter of about 585 miles (940 kilometers), Ceres is by far the largest member of the asteroid belt located between Mars and Jupiter. Although Ceres is the closest dwarf planet to Earth, for more than two centuries after its discovery in 1801, much remained unknown about it, as its surface features are barely visible to even the most powerful telescopes on Earth.

Then, in 2015, NASA's Dawn spacecraft became the first orbiter around Ceres. The probe revealed the dwarf planet's surface was covered in features resembling those from tectonic activity, such as a continent-like plateau and criss-crossing fractures.

These signs of geological activity on Ceres were surprising because they suggested the world's interior might still be warm. The collisions between the rocks that end up forming worlds can generate heat, but previous research suggested that a body as small as Ceres should have cooled off and lost any such heat a long time ago. 

Related: Biggest mysteries of the dwarf planet Ceres

Now research suggests heat from the decay of radioactive elements within Ceres might help keep it geologically active. The scientific team detailed their findings in the June issue of the journal American Geophysical Union Advances.

The scientists analyzed the interior of Ceres using computer models previously applied to bigger planets. Their results suggested that because Ceres is relatively small, it lacked a gravitational pull strong enough to result in powerful collisions to heat it up. As such, Ceres may have started off cold, instead of getting born hot like Earth, and similar larger worlds.

Over time, the decay of radioactive elements such as uranium and thorium within Ceres may have heated up the dwarf planet, until its interior became unstable.

"What I would see in the model is, all of a sudden, one part of the interior would start heating up and would be moving upward and then the other part would be moving downward," study lead author Scott King, a geoscientist in the Virginia Tech College of Science, said in a statement.

 Such instability might explain some of the surface features the Dawn mission saw on Ceres. For example, its large plateau formed on just one side of the dwarf planet, with nothing similar on the other side, and its criss-crossing fractures were clustered around the plateau in a single location. The concentration of these features in one hemisphere suggested instability concentrated on just one side of the asteroid.

"It turned out that you could show in the model that where one hemisphere had this instability that was rising up, it would cause extension at the surface, and it was consistent with these patterns of fractures," King said in a statement.

These findings suggest Ceres did not follow a planet's typical pattern of hot first and cool second, but a pattern of cool, hot and then cool again. "What we've shown in this paper is that radiogenic heating all on its own is enough to create interesting geology," King said in a statement.

King sees similarities between Ceres and the small icy moons of Saturn and Uranus. He looked forward to researching the interiors of those moons as well.

"Some of these moons are not too different in size from Ceres," King said in a statement. "I think applying the model would be really exciting."

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A new computer simulation suggests that dwarf planet Ceres may have been flung by the gravity of gas giant Jupiter toward the sun during the volatile era of planet formation 4.5 billion years ago. 

There has always been something out of place about Ceres. At 600 miles (1,000 kilometers) wide, Ceres is by far the largest body in the asteroid belt, the region between the orbits of Mars and Jupiter where space rocks (most of them only tens or hundreds of meters in size and oddly shaped) gather. 

Round like a planet, Ceres also contains some odd chemical compounds, such as ammonia, that are not present in its neighbors. Ceres' strange nature has long led scientists to believe that the dwarf planet is an intruder in the asteroid belt. A new simulation led by researchers from Sao Paulo State University in Brazil has now revealed a mechanism that may have displaced Ceres from its original birthplace in the distant past.

Related: Biggest mysteries of the dwarf planet Ceres

"In our article, we propose a scenario to explain why Ceres is so different from neighboring asteroids," Rafael Ribeiro de Sousa, a physics professor at Sao Paulo State University in Brazil and lead author of the new study told Universe Today. "In this scenario, Ceres began forming in an orbit well beyond Saturn, where ammonia was abundant. During the giant planet growth stage, it was pulled into the asteroid belt as a migrant from the outer solar system and survived for 4.5 billion years until now." 

While unseen in ordinary space rocks, ammonia is common in comets, the dirty snowballs that originate in the much colder outer reaches of the solar system and come to visit us from time to time, providing spectacular views to astronomers with their stunning tails of evaporating gas.

Cometary tails appear as comets arrive closer to the sun where temperatures are high enough to melt their ice. Something similar is going on with Ceres, which is the only object in the asteroid belt to have a thin atmosphere of evaporating water and ammonia ice, according to Universe Today.

But if Ceres formed where comets form, how exactly did it end up in the asteroid belt?

The key, the study suggests, is the powerful gravity of the gas giant Jupiter, which emerged as a major force during the formation of the solar system 4.5 billions of years ago. 

"Our simulations showed that the giant planet formation stage was highly turbulent, with huge collisions between the precursors of Uranus and Neptune, ejection of planets out of the solar system, and even invasion of the inner region by planets with masses greater than three times Earth's mass," Ribeiro de Sousa said. "In addition, the strong gravitational disturbance scattered objects similar to Ceres everywhere. Some may well have reached the region of the asteroid belt and acquired stable orbits capable of surviving other events." 

During this cosmic billiard period, there may have been up to 3,600 mini-planets the size of Ceres bouncing around the protoplanetary disk of dust and gas from which planets emerged. 

"With this number of objects, our model showed that one of them could have been transported and captured in the asteroid belt, in an orbit very similar to Ceres's current orbit," Ribeiro de Sousa said.

The study is not the first to have come up with such conclusions, according to Universe Today, but it contributes to the growing understanding of the early violent years of the solar system's formation.

"Our scenario enabled us to confirm the number and explain Ceres' orbital and chemical properties," Ribeiro de Sousa said. 

Astronomers know quite a lot about Ceres thanks to NASA's Dawn mission, which orbited first the dwarf planet, then asteroid Vesta, the second largest object in the asteroid belt, in the 2010s. The Dawn spacecraft ran out of fuel in 2018 while in orbit around Ceres. 

The study was published in the journal Icarus on May 17.

Follow Tereza Pultarova on Twitter @TerezaPultarova. Follow us on Twitter @Spacedotcom and on Facebook. 

This article was originally published at The Conversation. The publication contributed the article to Space.com's Expert Voices: Op-Ed & Insights.

Vahe Peroomian, Professor of Physics and Astronomy, USC Dornsife College of Letters, Arts and Sciences

"What is a dwarf planet?" — Myranda, age 8, Knoxville, Tennessee

The word "planet" came from the ancient Greek words that mean "wandering star." That makes sense, because for thousands of years, people have watched planets change position in the night sky — unlike stars, which appear fixed and unmoving to the naked eye.

That's how the ancients discovered five of the planets: Mercury, Venus, Mars, Jupiter and Saturn. Astronomers using telescopes found Uranus in 1781, Neptune in 1846, and Pluto in 1930.

Solar system leftovers

I'm a space scientist with a passion for astronomy and the exploration of the solar system. I received my Ph.D. in physics in 1994, about the time astronomers began to find more and more objects beyond Neptune, in the Kuiper belt. That's a place in space that holds the "leftovers" of the solar system — particularly small icy bodies.

Three of those icy bodies — Eris, Haumea and Makemake — were discovered in the early to mid 2000s. They seemed large enough to be planets; all of them are roughly the same size as Pluto.

Astronomers then surmised that there were likely many more of these icy bodies in the Kuiper belt. They began to wonder: How many planets might we end up identifying in our solar system? Twenty? Thirty? A hundred? More?

Dwarf planet defined

In 2006, and after much debate, the International Astronomical Union came up with a new definition for a planet. And for the first time, the term "dwarf planet" was used.

Here's what the IAU said: A planet has to orbit the sun directly. It also must be large enough to have a round, or spherical, physical shape.

And the planet must "clear its neighborhood." That means, aside from any moons it might have, the planet can't share its orbit with other objects of comparable size.

An object that satisfies only the first two criteria — but not the last — is now called a dwarf planet.

Pluto is demoted

That's why Pluto lost its status as a planet and is now classified as a dwarf planet. It failed the final item on the checklist — other icy Kuiper belt bodies are within its orbital path. The decision, a controversial one to be sure, is debated by scientists to this very day.

At the same time Pluto got demoted, another solar system object was promoted. Ceres, once considered an asteroid, is now classified as a dwarf planet. It's nowhere near the Kuiper belt; instead, Ceres is in the main asteroid belt, orbiting between Mars and Jupiter.

Add them up — Pluto, Ceres, Eris, Haumea and Makemake — and that brings the number of dwarf planets in our solar system to five. But that list is sure to grow. Already, hundreds of candidates, nearly all in the Kuiper belt, potentially satisfy the criteria to be a dwarf planet.

About the dwarf planets

Dwarf planets are nothing like Earth.

As their name implies, they are much smaller. Pluto and Eris, the largest of the dwarfs, have less than one-fifth the diameter of the Earth.

They have less mass, too. For example, Earth has about 6,400 times more mass than Ceres. That’s like comparing two killer whales to a guinea pig.

And dwarf planets are cold. Pluto's average temperature is around minus 400 degrees Fahrenheit (minus 240 Celsius).

Could life exist on a dwarf planet?

Three things are needed for life: liquid water, an energy source and organic molecules — that is, molecules containing carbon.

More than 100 miles (161 kilometers) below Pluto's surface, an enormous ocean of liquid water may exist; this might also be true for other Kuiper belt worlds. Ceres also has subsurface water, remnants of what might have been an ancient global ocean.

Organic molecules, in abundance everywhere in our solar system, have been found on Ceres and Pluto.

But the one missing ingredient for all the dwarf planets is a source of energy.

Sunlight won't work, particularly for the Kuiper belt dwarfs; they are simply too far away from the sun. To reach the belt, the light must travel more than 2.7 billion miles (4.4 billion km). By the time the sunshine arrives at these distant worlds, it's too weak to significantly heat any of them.

And all the dwarf planets are too small to hold the inner heat that remains from the solar system's formation.

Yet scientists have discovered life on Earth in the most hostile places imaginable – near the bottom of the ocean, miles deep in the soil and even inside an active volcano. When it comes to life in our solar system, never say never.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Follow all of the Expert Voices issues and debates — and become part of the discussion — on Facebook and Twitter. The views expressed are those of the author and do not necessarily reflect the views of the publisher.

Paul M. Sutter is an astrophysicist at SUNY Stony Brook and the Flatiron Institute, host of "Ask a Spaceman" and "Space Radio," and author of "How to Die in Space." Sutter contributed this article to Space.com's Expert Voices: Op-Ed & Insights.

Ceres, the most dominant member of the asteroid belt, doesn't look like the other asteroids. Most notably, it has a lot of ammonia on its surface, which other asteroids tend to lack. The only place to get a lot of ammonia is in the outer regions of the solar system in the early days of its formation. 

In a new paper, researchers propose a possible explanation for why Ceres is so different from its neighbors: Perhaps the dwarf planet began in an orbit beyond Saturn and, during a massive reshuffling of the outer planets, got planted into the asteroid belt, where it has remained to this day.

A Ceres matter

With a radius of 296 miles (476 kilometers), Ceres is by far the largest object in the main asteroid belt, the loose collection of rocks between the orbits of Mars and Jupiter. The vast majority of asteroids are far smaller than Ceres; in fact, by itself, Ceres accounts for over one-third of the entire mass of the belt.

And Ceres is weird.

Related: Biggest mysteries of the dwarf planet Ceres

NASA's Dawn spacecraft spent several years in orbit around Ceres, mapping and studying its surface. That mission found that the surface is a mixture of water ice minerals bound with water, like clay and carbonates. Beneath that is a mantle rich in water ice surrounding a core of mainly solid rock.

Ceres has a relatively low density (2.2 grams per cubic centimeter) and a rather low albedo, meaning it's not very reflective. This makes Ceres very similar to the most common kind of asteroid, the C-type — or carbonaceous chondrite — asteroids. Indeed, Ceres' location within the main asteroid belt puts it close to other C-type asteroids.

But most C-type asteroids don't have that much water and don't have so many clays. And Ceres also has a lot of ammonia on its surface, which almost all other asteroids lack. Ammonia isn't common in the inner solar system, where the intense heat of the sun evaporated it in the early days of the system's formation. Instead, ammonia survived only beyond the "ice line," the distance from the sun where volatile elements like ammonia could survive.

Indeed, Ceres doesn't really look, smell or act like an asteroid. Instead, the dwarf planet has more in common with the most distant objects in the solar system — the members of the Kuiper Belt, like Pluto, Charon and Eris.

Scientists have proposed explanations for each strange trait. Maybe Ceres formed inside the asteroid belt, in a really weird way that allowed it to maintain a lot of water. Maybe it formed without disrupting the rest of the main belt. Maybe over the course of billions of years, a lot of ammonia floated in from the outer solar system and found itself on the surface of the dwarf planet (and not the other asteroids).

Or maybe, the authors of the new paper propose, Ceres was born beyond the orbit of the giant planets and got sent into the asteroid belt long ago.

A song of ice and also ice

The early solar system was a chaotic place. Thousands of small celestial bodies called planetesimals jostled and fought for dominance, aggregating into planets only to be smashed apart again. Among these multitudes was a vast population sitting outside the giant planets, according to the new paper, posted to the preprint database arXiv.

The most common model of the early solar system, called the Nice model (named for the city in France where a conference on solar system formation took place), states that the giant planets of the solar system formed closer to the sun, and closer to one another, than their present-day locations. Some versions of the Nice model also

When those planets began to migrate to their modern positions, it shook things up a lot. The large population of Kuiper Belt objects were disrupted, their orbits perturbed by the motions of the giant worlds. Some of them were ejected completely from the solar system. Some crashed into each other and were obliterated. Some were captured, as in the case of Neptune's moon Triton.

And perhaps others made their way into the inner solar system.

Homeward bound

But even if Ceres-type worlds made it into the asteroid belt, it wasn't smooth sailing from there. Astronomers already knew that the disturbances of the outer system affected even the asteroids, causing the belt to lose up to 80% of its objects. So it was a serious challenge for something like Ceres to end up in the asteroid belt and persist to the present day.

It required a lot more objects like it. The researchers estimated that if at least 3,500 Ceres-size objects existed beyond the orbit of Saturn in the early solar system, at least one of them would make it into the asteroid belt and stay there. Those estimates are based on computer simulations that tracked the evolution of planetary orbits during the disruptive phase of the outer-planet migration. Thousands of Ceres-size objects sounds like a lot, but it's actually well within the range that other models suggest for populations of the outer system. 

The conclusion: The most likely explanation for Ceres is that it was born in the icy edges of the solar system and was the luckiest member of a group of objects that were displaced when the giant planets shifted their positions.

The asteroid belt and the Kuiper Belt remain some of the best laboratories for understanding the formation of the solar system. Any model of planetary formation and evolution must include their effects on the smallest objects orbiting the sun. And so Ceres just may be the major clue we need to understand what happened in the solar system over 4 billion years ago.

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Ceres might be spewing cryovolcanoes in yet another spot on the dwarf planet's surface.

Close-up pictures from NASA's Dawn mission that orbited Ceres between 2015 and 2018 revealed salt deposits in a crater known as Urvara, spotted for the first time in a new study. The salt deposits may be associated with icy volcanoes, the research team says, whose brine rose to the surface over time.

Given there are multiple zones on Ceres with salt deposits, the implication is there might be a source of salt underneath the asteroid's surface, such as a possible saline ocean. (The salts, however, might have come from the impact that formed Urvara 250 million years ago instead.)

Photos: The changing bright spots of dwarf planet Ceres

The larger implication is what water could mean on a relatively small world that is less than 300 miles (482 kilometers) in diameter, especially in terms of understanding the formation of Ceres and larger dwarf planets like it. This is far from the first study to suggest a possible global ocean hidden inside Ceres and adds to years of speculation about how so much liquid water could be possible in a tiny world far out in the solar system.

"The large impact structures on Ceres give us access to the deeper layers of the dwarf planet," lead author Andreas Nathues, a scientist at the Max Planck Institute for Solar System Research (MPS) in Göttingen, Germany, said in a statement.

Natheus pointed out that the topography and composition of the craters seems to indicate "complex and long-lasting geological processes that have altered the dwarf planet's surface." The 105-mile-wide (170 km) Urvara is an example of this; the asteroid that formed the crater 250 million years ago excavated material from as deep as 31 miles (50 km) below the surface.

The team mostly relied upon images taken by Dawn during its extended mission, which brought the spacecraft to within just 22 miles (35 km) of the surface to take high-resolution photography. MPS' two Dawn Framing Cameras obtained the data that was used in the study.

The images showed a "geologically distinctly diverse landscape" within Urvara, the researchers said in the release, including terraced crater walls, a large mountain range, sharp cliffs and most importantly for the cryovolcano argument, bright material that looks a lot like the salts found in the more famous Occator crater.

The salts are notable not only for their potential for cryovolcanoes, but also because they are close to organic compounds, meaning the carbon-containing building blocks of life as we know it. It's the first time salt deposits and organic compounds were found combined on the surface. They were particularly concentrated on a slope west of the central mountains, researchers said.

The organics find has "important implications for the overall geologic history of Ceres as well as potential links to astrobiology and habitability," noted scientist Guneshwar Thangjam, who is at the National Institute of Science Education and Research in Bhubaneswar, India. 

The team will compare the Urvara organics to those found in another crater, Ernutet, to better answer those astrobiology and habitability links, Thangjam added.

A study based on the research was published Tuesday (Feb. 22) in Nature.

Follow Elizabeth Howell on Twitter @howellspace. Follow us on Twitter @Spacedotcom and on Facebook. 

A rare version of the radioactive element plutonium embedded in Earth's crust below the deep sea is providing new clues as to how heavy metals form in the stars.

The new research finds that the isotope, called plutonium-244, may arrive on Earth in tandem with iron-60, a lighter metal known to form in supernovas, explosions that occur during the death throes of many types of stars. This finding suggests that supernovas may create both heavy metals — although it's possible that other events, such as the mergers of neutron stars, are responsible for at least some of the plutonium-244.

Understanding how heavy elements formed is one of the top three most burning questions in physics, said Anton Wallner, a nuclear physicist at the Australian National University and the Helmholtz Center Dresden-Rossendorf, a research center in Germany. Half of elements heavier than iron are built in the hearts of stars through a fairly well-understood process of fusion. The other half, though, requires a high density of free neutrons to form. This means they must form in a more explosive environment than a typical star core — supernovas, perhaps, or massive events such as a neutron-star merger or a collision of a black hole and a neutron star.

Related: Elementary, my dear: 8 elements you’ve never heard of

Along with collaborators in Japan, Australia and Europe, Wallner was interested in finding out if he could discover fingerprints of these celestial events on Earth. There are some radioactive versions of heavy metals that don't occur naturally on the planet. In particular, the researchers were on the hunt for plutonium-244, a variation of plutonium with a half-life of 80.6 million years. This means it takes 80.6 million years for radioactive decay to eat away at half of the initial plutonium produced. Any plutonium-244 originally present during Earth's formation has long since decayed, so any atoms the researchers could find would have to be extraterrestrial in origin.

"Can we find plutonium-244 on Earth?" Wallner said. "Then we know it's coming from space."

Rare metals 

To hunt for these rare atoms, the researchers turned to samples of Earth's crust from nearly 5,000 feet (1,500 meters) below the Pacific Ocean. These rocks form so slowly that a millimeter of crust records 400,000 years of history, Wallner told Live Science. The sample covered the past 10 million years.

The researchers then probed the samples for iron-60 — the extraterrestrial version of iron that forms in supernovas — and for plutonium-244. They found both. 

It was no surprise to find iron-60, Wallner said, as previous research had already shown fluctuations in iron-60 levels in deep-sea sediments and crust over time. The findings confirmed what researchers had previously suspected: There were two increases in iron-60 — one that occurred between 4.2 million and 55 million years ago, and one that happened sometime before 7 million years ago. These influxes of the metal may have been the result of two fairly nearby supernovas, Wallner said.

"The supernova that happened and produced the iron-60 must have been spectacular at the time," he said. "It must have been similar [in brightness] to the full moon, so you would see it even in daytime."

In the past, the researchers did not have sensitive enough methods to accurately count the extremely rare atoms of plutonium-244 scattered in Earth's crust. But in the new study, using cutting-edge technology and methods, they did. The timing of this extraterrestrial plutonium's arrival on Earth is a bit harder to pin down, as the researchers had to search layers of crust corresponding to between 3 million and 5 million years of history. However, the influx of plutonium-244 did correlate with the influx of iron-60.

"The ratio of plutonium-244 to iron-60 seems to be constant," Wallner said. This suggests that both might come from a common origin.

Forged in stars 

Although the coordinated arrival of plutonium-244 and iron-60 suggests that both could have come from supernovas, a lot of questions remain. Computer models that attempt to mimic the formation of elements within supernovas really struggle to generate heavy-element formation, Wallner said. The ratio of iron-60 to plutonium-244 found in the new study suggests that the plutonium-244 would be a lot less prevalent than iron-60 after the stellar explosion, perhaps just a small percentage of the total elements formed.

It's also possible, Wallner noted, that the plutonium-244 atoms discovered in the deep-sea crust didn't come from a supernova at all. The plutonium-244 could have been formed in an earlier event and may have been floating aimlessly in deep space when a blast of iron-60 whooshed through, pushing the heavier plutonium-244 along with it. In that situation, both elements would have arrived on Earth at the same time, but the plutonium-244 would be a lot older.

To explore that possibility, the researchers want to look at different classes of atoms with different half-lives. The half-lives act like a clock so that scientists can determine a range of estimates for the ages of the elements. If the plutonium-244 were found in concert with an element of a much shorter half-life, for example, it would suggest that both were younger and fresher. It would also suggest that the amount of plutonium-244 produced in a supernova was lower and that more of it may have come from other events, like a neutron-star merger.

The research team is already studying a piece of crust 10 times larger than the one in this research. Having a larger piece of crust will allow researchers to expand their search for plutonium-244 atoms and get a more precise timeline of when those atoms arrived on Earth.

"What is fascinating is that you find some six or 10 atoms which you can identify in the end as not from Earth but from space, and then you get some hints about where it had been produced and when it had been produced," Wallner said.

The research was published today (May 13) in the journal Science.

Originally published on Live Science.

The first known visitor from interstellar space, 'Oumuamua, was likely a pancake-shaped chip off a Pluto-like world, researchers say.

These findings may shed light on the stuff a new class of planet, an exo-Pluto, is made of, scientists added.

Astronomers first detected the mysterious visitor named 1I/'Oumuamua — meaning 'scout' or 'messenger' in Hawaiian — in 2017. 'Oumuamua's speed and trajectory revealed it originated outside the solar system, making it the first known interstellar object.

Related: 'Oumuamua: Solar system's 1st interstellar visitor explained in photos

The second known interstellar object, 2I/Borisov, was detected in 2019. Borisov was very clearly a comet, spewing out gases and possessing a composition much like comets long seen in the solar system.

An interstellar comet? Asteroid? Something else?

In a number of key ways, 'Oumuamua resembled a comet. For example, scientists could not explain its movements through space by the force of gravity alone. This suggested 'Oumuamua was jetting out gas from its sunlit side that was pushing it like a rocket, study co-author Steven Desch, an astrophysicist and planetary scientist at Arizona State University in Tempe, told Space.com.

However, if 'Oumuamua was a comet, it was unlike any previously seen in the solar system. It lacked any detectable escaping gas, unlike the big tails typically spotted streaming from comets. In addition, its shape — resembling either a cigar or a pancake — was unlike any known comet. Moreover, the rocket-like push seen from 'Oumuamua was stronger than what researchers expected from comets.

All these bizarre features 'Oumuamua's even led some researchers to speculate that it had alien origins.

"Everybody is interested in aliens, and it was inevitable that this first object outside the solar system would make people think of aliens," Desch said in a statement. "But it's important in science not to jump to conclusions."

Now scientists find 'Oumuamua might not be a piece of alien technology, but a chip off a Pluto-like world.

A strange new object

Researchers speculated that 'Oumuamua was not made largely of water ice like known comets, but perhaps of other kinds of ices. They calculated how quickly such ices would sublimate — convert from a solid directly to a gas — as 'Oumuamua flew by the sun, and the rocket-like push it would get from these escaping gases. 

The scientists also noted some ices are far more reflective than often assumed. If 'Oumuamua was made from these shiny ices, it might be smaller than previously estimated based on the light that astronomers detected from it. A tinier size for the interstellar visitor would mean any push from sublimating gases would have a larger effect than usually seen with comets, helping explain the unexpected speed with which it zipped away from the sun.

The researchers found one ice in particular — solid nitrogen — could explain all of 'Oumuamua's features and behavior. Solid nitrogen ice is seen on the surface of Pluto and Triton, suggesting this interstellar visitor could be made from the same material. "It was very satisfying to refine our calculations and see everything fall into place," Desch said.

Any nitrogen gas escaping from 'Oumuamua would have proven very difficult for astronomers to detect with the telescopes used to monitor it. "In essence, there was a tail like one would expect for a comet, it is just that because of what it is made of, we didn't detect it," study co-author Alan Jackson, an astrophysicist and planetary scientist at Arizona State University in Tempe, told Space.com.

An interstellar flapjack

These new findings suggest 'Oumuamua was shaped more like a pancake than a cigar. It may also be smaller than previously thought — just 147 by 144 by 24 feet (45 by 44 by 7.5 meters) in size when astronomers first detected it. In comparison, prior estimates suggested 'Oumuamua was about 1,300 feet (400 m) long.

The researchers suggested that 'Oumuamua likely wasn't flat when it first entered the solar system. However, the light from the sun ultimately eroded it to a sliver, wearing away more than 95% of its mass.

"The same thing should happen with water-ice comets, but at a much smaller level," Jackson said. Water ice sublimates much slower than nitrogen ice, Desch explained. In addition, Jackson noted 'Oumuamua may have stayed together as one piece as it sublimated because it was made all of the same material — in contrast, most comets in the solar system are mixtures of rock, water ice and other ingredients, "so they tend to evaporate unevenly. This is partly why comets often break up when they pass very close to the sun."

'Oumuamua origin: How our mysterious interstellar visitor may have been born

These findings suggest interstellar objects such as 'Oumuamua may give us our first view of a hitherto unknown type of planet — an exo-Pluto. All in all, 'Oumuamua may be the first known sample of an exoplanet brought into the solar system, the researchers said. 

"The thought that what we saw could be a chunk of an actual exoplanet is thrilling," Desch said.

Piece of an exo-Pluto

Based on 'Oumuamua's speed and trajectory, the researchers suggested this fragment of nearly pure nitrogen ice was slung away from a young star system about 400 million to 500 million years ago, possibly from the Perseus arm of the Milky Way. When it comes to what to call this potentially new class of objects, Desch suggested exo-Pluto fragments or Pluto-like fragments, whereas Jackson suggested nitrogen-ice comets.

The scientists calculated the rate at which cosmic impacts would have knocked chunks of ice off the surfaces of Pluto and similar bodies over the course of the solar system's history. They estimated such collisions might have generated 100 trillion fragments, about half of which are water ice and the other half nitrogen ice. All in all, "about 1 in 1,000 comets in our solar system must be objects like 'Oumuamua," Desch said. One such example may be the comet C/2016 R2, discovered in 2016, he noted.

The researchers also calculated the chances that a nitrogen-ice comet from another star would reach our solar system. Their findings suggested "the outer reaches of a lot of planetary systems look very much like our own," Jackson said. "It is difficult to get information about the outer reaches of exoplanetary systems with the methods that we usually use to look for planets, so this gives us a unique way to get a sense of what exoplanetary systems are like."

Future telescopes such as the Vera Rubin Observatory in Chile could help regularly scan huge swaths of the sky and detect even more interstellar objects to learn more about them. In addition, "there has also been some work on concepts for space missions that could intercept a future object like 'Oumuamua," Jackson said. "That to me is an incredibly exciting prospect — an up close look at something that originated from outside our solar system."

The scientists detailed their findings online March 16 in a study divided into two papers, which you can find here and here, in the Journal of Geophysical Research: Planets, and at the Lunar and Planetary Sciences Conference.

Originally published on Space.com.

For a few months in 2018, as NASA's Dawn spacecraft used up its last drops of fuel, it gave scientists an incredibly detailed look at one of the strangest places in the solar system: Occator Crater.

That's the name of a massive impact site on the dwarf planet Ceres, tucked away in the asteroid belt. In the mission's last months, Dawn flew just 22 miles (35 kilometers) above the dwarf planet's surface and focused its energies on Occator Crater. Earlier observations from the mission had suggested that some sort of geological activity was bringing saltwater to the surface, and scientists wanted a closer look.

Now, initial analysis of those final months of science suggest that Ceres may have been active much more recently than scientists had dared to imagine, according to an article summarizing seven different research papers published today (Aug. 10) in the journals Nature Communications, Nature Geoscience and Nature Astronomy.

In Photos: The changing bright spots of dwarf planet Ceres

Ceres: A strange dwarf planet 

"Dawn accomplished far more than we hoped when it embarked on its extraordinary extraterrestrial expedition," Mission Director Marc Rayman of NASA's Jet Propulsion Laboratory in California said in a NASA statement. "These exciting new discoveries from the end of its long and productive mission are a wonderful tribute to this remarkable interplanetary explorer."

The new research papers focus on a host of different intriguing findings about Occator Crater, which is about 22 million years old and about 57 miles across (92 km), as well as about Ceres more generally.

One of the new papers, for example, constructs a detailed timeline of geological events at the crater, hypothesizing that cryovolcanism began just 9 million years ago and continued for several million years. A series of bright deposits formed over that time from brine seeping out from Ceres' mantle through the upper layer of rock, with activity continuing as recently as a million years ago.

And this volcanism, the authors argue, is unlike any other in the solar system, since it occurs on a relatively small object that isn't subject to the gravitational tugs experienced by places like Jupiter's ultra-volcanic moon Io.

Another paper identifies a specific form of salt found so far only on Earth and now on Ceres that is particularly short-lived, on the scale of centuries, according to a statement. The combination suggests that the brines that deposited them on the surface must have done so very recently and perhaps continue to move through the asteroid today. These salts could also solve the puzzle of what's keeping Ceres relatively warm without gravitational tugging and could be responsible for maintaining pockets of liquid within the asteroid.

And the impact that created Occator Crater itself may have brought enough heat to the dwarf planet to trigger the brine seepage that left bright deposits at the surface by forcing the brine through older cracks in the rock.

Another paper attempts to identify where the brine in different patches of the crater came from, suggesting that certain areas come from water in the melted subsurface pool created by the impact itself and some from an older and deeper, more global reservoir on Ceres.

Other papers in the new batch of research analyze how Ceres' crust differs in different locations, how the mounds and hills inside the crater may have formed and how the salty deposits compare to activity on the moon and on Mars.

Although Dawn's final months revolutionized scientists' view of the dwarf planet and its large crater, the new research doesn't satisfy curiosity about this ocean world asteroid and may lay the groundwork for a new mission to Ceres, according to an overview paper released with the new findings.

Email Meghan Bartels at mbartels@space.com or follow her on Twitter @meghanbartels. Follow us on Twitter @Spacedotcom and on Facebook.

Two incredibly strange celestial objects whose discoveries trace, in part, to observatories at the summit of Maunakea now carry the peak with them in official names inspired by Hawaiian culture.

Their connection to Hawaii is all these two objects share. One is a quasar, a massive source of energy that scientists believe stems from a distant black hole — in this case, the quasar was born just 700 million years after the Big Bang and could contain the mass of 1.5 billion suns. The other object is much closer to us, a dwarf planet in our solar system that requires 40,000 years to complete a single orbit of our sun.

"We only want to name the really unique things, because there are literally like billions and billions and billions of things out there," Ka'iu Kimura, executive director of the 'Imiloa Astronomy Center, a museum and cultural center based in Hilo, Hawaii, that helps run the naming program, told Space.com in January at the 235th meeting of the American Astronomical Society.

Related: The Thirty Meter Telescope: How a volcano in Hawaii became a battleground for astronomy

The program, called A Hua He Inoa, is dedicated to finding Hawaiian names for astronomical objects discovered using the dozen telescopes atop Maunakea, at the heart of the island of Hawaii and a deeply contested site. But the program doesn't simply slap an existing name onto a discovery.

Instead, it brings astronomers and native Hawaiians — students, teachers or both — together to create a name grounded in traditions but tailored to the details of the discovery and how it resonates with a Hawaiian way of being in the universe. "You have to sit and explain to youth and hear their feedback," Kimura said of the scientists who have taken part. "We also put language and culture experts in that conversation."

An earlier version of the program, which relied more heavily on a specific Hawaiian language and cultural expert, most famously named the first interstellar asteroid to be discovered, now called 'Oumuamua, and the black hole that scientists released an image of last spring, called Pōwehi.

More recently, the International Astronomical Union, which oversees all celestial naming, adopted Hawaiian names developed through the program for two asteroids. Now, with the newly discovered quasar and the dwarf planet, the tally has reached a half dozen objects.

The group of Hawaiian teachers who developed the new name for the quasar, Pōniuāʻena, which would otherwise be referred to as J1007+2115, were inspired by the name Pōwehi to begin with "pō." In both names, the syllable represents the deep darkness of a black hole and derives from the Kumulipo, a native Hawaiian chant which tells the story of the creation of the islands.

But a quasar has brightness as well as darkness, which the teachers incorporated into the name. 

"They were so impressed by the look and the motion of the quasar and how it's spewing out all of these heat and light," Kimura said of the participants. "It's spinning so fast and so radiantly that it glows brilliantly." That's where the latter portion of the name comes from, she said. "The name, Pōniuāʻena, evokes the unseen spinning source of creation, surrounded by brilliance," a statement from 'Imiloa explains.

The discovery was made using data from three different facilities atop Maunakea: W. M. Keck Observatory, the International Gemini Observatory and the University of Hawaii-owned United Kingdom Infrared Telescope.

Scientists first discovered the other newly named object, in 2015 using Japan's Subaru Telescope on the mountain. Before it earned an official name, the dwarf planet was nicknamed The Goblin, inspired by the letters TG in its arbitrary designation based on scientists' first observations of it.

While it's in our solar system, the dwarf planet isn't particularly neighborly. At its closest, the object comes within about 65 astronomical units (AU) — 1 AU is the average distance between the Earth and the sun, about 93 million miles or 150 million kilometers; at the most distant point in its orbit, it strays about 2,300 AU away from the sun. It lies out beyond Pluto and traces a long orbit around the sun, with one year on the body lasting about 40,000 Earth years.

It's that epic journey around the sun that inspired the new Hawaiian name for the object, Leleākūhonua, that a group of students developed through the program. "The kids were inspired by this bird, the kolea," Kimura said, referring to a species also known as the Pacific Golden-Plover.

The plover spends its summers in Alaska and its winters in Hawaii, clocking as much as 2,000 miles (3,200 kilometers) in a single flight, according to the National Audubon Society. For the students in the naming program, that sounded an awful lot like the dwarf planet.

"They only come here once a year," Kimura said of the plovers. "They feed and they get a little chubbier and then they fly back," much like how the dwarf planet gains energy when it is closer to the sun, before migrating back out to the icy reaches of the solar system. The name Leleākūhonua was approved by the International Astronomical Union and announced on June 3.

For Kimura, each of these new names is about recognizing the unique culture and tradition of the Hawaiian islands, and honoring the fact that context can influence the science done in such a place. But names aren't enough for her, even names that are chosen with such a detailed process.

"To me, the win would be we'd see more Hawaiian students getting into science, we would see more and hear more of our language and our culture being spoken at these places of research," Kimura said. "We would promote globally the uniqueness of Hawaii, which really is its people, its language, its culture, and if astronomy can help give Hawaii — and any community that it is being done in across the world — that kind of recognition, honor and promotion, that is I think a big win."

Email Meghan Bartels at mbartels@space.com or follow her on Twitter @meghanbartels. Follow us on Twitter @Spacedotcom and on Facebook.

The asteroid Hygiea may qualify as a dwarf planet — and it could steal the title of the smallest dwarf planet in the solar system!

Astronomers have captured high-resolution imagery of Hygiea, the fourth largest rock in the Asteroid Belt. And low and behold, Hygiea is spherical in shape. That's a pretty important dwarf-planet marker, and the only one Hygiea was missing until now. 

Asteroids boast a variety of shapes, but the rounded shape of dwarf planets shows that they had enough mass for its own gravity to pull it into this round shape. Hygiea already met the other requirements for dwarf-planet classification since it orbits the sun, is not a moon orbiting another planet and has not cleared other objects out of its own orbit.

Video: Asteroid Hygiea May Be Smallest Dwarf Planet in Our Solar System
Related: Meet the Solar System's Dwarf Planets

So, how big is this potential new member of the dwarf planet family? The team of astronomers, led by researcher Pierre Vernazza of the Laboratoire d'Astrophysique de Marseille in France constrained Hygiea's size, and estimated its diameter is just over 267 miles (430 kilometers). For comparison, Hygiea is less than one-fifth the width of its most famous cousin, Pluto, which has a diameter of about 1,491 miles (2,400 km). 

Ceres held the title of smallest dwarf planet until now, with a diameter of almost 590 miles (950 km). 

Before Hygiea can be officially upgraded to dwarf planet status, the International Astronomical Union — the same group of astronomers who were responsible making Pluto a dwarf planet — must review all the evidence and take a vote. 

Video: Where is Hygiea in Our Solar System?

"Thanks to these images, Hygiea may be reclassified as a dwarf planet, so far the smallest in the solar system," Vernazza said in a statement from the European Southern Observatory (ESO), which manages the SPHERE instrument that produced the high-resolution imagery in the study. SPHERE (which stands for Spectro-Polarimetric High-contrast Exoplanet Research) sits atop the Very Large Telescope at ESO's Paranal Observatory in Chile.

"Thanks to the VLT and the new generation adaptive-optics instrument SPHERE, we are now imaging main belt asteroids with unprecedented resolution, closing the gap between Earth-based and interplanetary mission observations," Vernazza added.

A study detailing the new findings was published today (Oct. 28) in Nature Astronomy. 

• Dwarf Planets of Our Solar System (Infographic)
• The Asteroid Belt May Be a 'Treasure Trove' of Planetary Building Blocks
• Why Isn't Pluto a Planet Anymore?

Follow Doris Elin Urrutia on Twitter @salazar_elin. Follow us on Twitter @Spacedotcom and on Facebook. 

Eris was one of the first dwarf planets to be discovered in the solar system. It is almost the same size as Pluto, and its discovery directly led to the former ninth planet's demotion. Eris also has a moon, Dysnomia, which was discovered not long after Eris.

Is Eris a planet or a dwarf planet?

When Eris was first discovered in 2005, astronomers thought it was significantly larger than Pluto and even considered whether or not Eris could be the 10th planet in our solar system. Ultimately, however, Eris' discovery and learning it was such a small planet was why astronomers wound up demoting Pluto to dwarf planet status in 2006. That decision remains controversial to this day, making Eris' name fitting.

"Eris is the Greek goddess of discord and strife," astronomer Mike Brown, a member of the Eris discovery team, said in a statement from the California Institute of Technology. "She stirs up jealousy and envy to cause fighting and anger among men. At the wedding of Peleus and Thetis, all the gods were invited with the exception of Eris, and, enraged at her exclusion, she spitefully caused a quarrel among the goddesses that led to the Trojan War."

Like almost all of the known dwarf planets (with the exception of Ceres), Eris lies in the Kuiper Belt, which rings the outer solar system. But Eris is even farther-flung than Pluto, circling our star about three times farther away. It takes 561 years for the distant dwarf planet to make a single trip around the sun, though it rotates once every 25 hours, making the length of its day very similar to a day on Earth.

Watching Eris

Eris' distance allowed astronomers to make precise measurements when the dwarf planet passed in front of a dim star in 2010, in an event known as an occultation. In addition to measuring Eris’ size, researchers were also able to determine its shape, size and mass.

The observations helped scientists determine that Eris' diameter is 1,445 miles (2,326 kilometers), give or take 7 miles (12 km). That makes it slightly smaller than Pluto. When New Horizons reached Pluto, the spacecraft measured the diameter of the planet and found it to be 1,473 miles (2,370 km) across, which is about two-thirds the diameter of Earth's moon.

Newer studies show that Eris likely is a spherical body. And, by studying the motion of Eris' moon, Dysnomia (which was also discovered in 2005), they estimate the dwarf planet is about 27% heavier than Pluto, which means it's denser than Pluto as well.

Eris' surface was also found to be extremely reflective, bouncing back 96% of the light that hits it. That makes Eris one of the most reflective bodies in the solar system, roughly on par with Saturn's icy moon Enceladus. [Top 10 Extreme Planet Facts]

Researchers think Eris' surface is probably composed of a nitrogen-rich ice mixed with frozen methane in a layer less than 1 millimeter thick. This ice layer could be the result of the dwarf planet's atmosphere condensing as frost on the surface as it moves away from the sun, they said.

Astronomers estimated that the side of the dwarf planet facing the sun likely gets no warmer than minus 396 degrees Fahrenheit (minus 238 degrees Celsius), while temperatures on the night side would be even lower.

Future Eris research

The extreme distance of Eris, coupled with its small size, make it difficult to observe the dwarf planet without powerful telescopes and advanced technology. 

While there are no spacecraft expected to fly by Eris in the near future, researchers will get a better look at the dwarf planet after the James Webb Space Telescope launches in 2021. The JWST website specifically mentions Eris as a target of interest and adds that the telescope will look at small objects in the solar system to better characterize what their landscapes are made of.

Separately, a group of astronomers (including Alan Stern, the principal investigator of the Pluto mission New Horizons) has asked the community to reconsider the International Astronomical Union's definition of "planet." They propose that all dwarf planets be made planets, which would also include Eris.

Additional resources: 

• Check out the photos of Eris from NASA's Jet Propulsion Laboratory. 
• Learn more about Eris from NASA's Solar System Exploration page. 
• Read the detailed account of discovering Eris from Caltech astronomer Mike Brown's blog. 

This article was updated on July 10, 2019 by Space.com Contributor Elizabeth Howell. 

Two NASA telescopes peered more closely than ever before at a planet shedding gas into space.

NASA's Hubble and Spitzer space telescopes together discovered the chemical "fingerprint" of the planet, called Gliese 3470 b or GJ 3470 b. The planet was already a puzzle because it orbits extremely close to its parent star that is literally evaporating. It's nearly 13 times the size of Earth, comparable to Neptune, which clocks in at 17 Earth masses. And what scientists found when they looked at the planet more closely was a big surprise.

The scientists predicted GJ 3470 b's atmosphere would be full of oxygen and carbon, the same elements that are at the root of the water vapor and methane gas observed at Neptune. "Instead, we found an atmosphere that is so poor in heavy elements that its composition resembles the hydrogen- [and] helium-rich composition of the sun," Björn Benneke, lead author on the new research and an astronomer at the University of Montreal, said in a statement.

Related: The Most Fascinating Exoplanets of 2018

What's more, the team thinks they may know why GJ 3470 b's composition is so different than that of Neptune's: It has to do with the planet's origin story.

Astronomers have already spotted many much larger exoplanets that orbit extremely close to their parent stars, known as "hot Jupiters." Many scientists suspect that these Jupiter-size planets formed farther out in their respective solar systems before migrating in toward their stars.

That's not the case for GJ 3470 b, however. The star likely formed just where it is now, extremely close to a red dwarf star that is about half the size of our own sun. The planet probably started out as a dry rock, and then picked up hydrogen from the gas disk surrounding the star when the star was very young. (This is called a "protoplanetary disk" and is a common feature in young star systems.)

Commonly, planets such as GJ 3470 b rapidly grow into hot Jupiters, but that's clearly not the case here. "This is an intriguing regime," Benneke said. One explanation could be that the disk of protoplanetary gas somehow dispersed while the planet was still growing, stunting its size forever. 

The two NASA telescopes did their work by studying the planet closely as it orbited around the star. Fortunately for scientists, GJ 3470 b passes directly across the disk of its parent star, which allows scientists to pick out the chemical fingerprint of the planet through spectroscopy. The researchers looked at two features of the star's light: how much light was absorbed by the planet as it passed in front of its star (which they observed 12 times) and how much reflected light was lost from the planet when it went behind the star (which they observed 20 times).

Chances are, astronomers will be stuck on the GJ 3470 b puzzle until they have access to a more powerful observatory — but one is on its way to orbit in a few years. NASA's James Webb Space Telescope could probe the planet after the observatory launches in 2021 or so. Webb is more sensitive to the infrared wavelengths in which the planet shines brightly, so it will be able to see more detail about the world than Hubble or Spitzer can, the team said.

A paper based on the research was published July 1 in the journal Nature Astronomy.

• Sweet Super-Puffs: These 2 Exoplanets Have the Density of Cotton Candy
• Exoplanet Hunters Have a New Plan to Spot Hidden 'Migrating' Worlds
• The Strangest Alien Planets (Gallery)

Follow Elizabeth Howell on Twitter @howellspace. Follow us on Twitter @Spacedotcom and on Facebook.

Ceres, the closest dwarf planet to Earth, may be wrinkling as it shrinks, a new study finds.

With a width of about 585 miles (940 kilometers), Ceres is both a dwarf planet and the largest member of the asteroid belt located between Mars and Jupiter. Previous research found that the dwarf planet was not made up solely of rock, but composed partly of both icy and rocky material.

Icy moons a bit larger than Ceres, such as Jupiter's moons Europa and Ganymede, possess rifts and other features on their surfaces, which prior studies have suggested are a result of their cooling. Liquid water is more dense than ice, which is why ice floats on water, so as Europa and Ganymede cooled over time, the resulting ice expanded their interiors, cracking their surfaces, the idea goes.

Related: Photos: Dwarf Planet Ceres, the Solar System's Largest Asteroid

In contrast, rocky worlds such as Mercury and Mars possess wrinkles on their surfaces that previous research suggested are a product of their shrinking. Solid rock is more dense than molten rock, so as Mercury and Mars cooled and their rock solidified, they contracted, generating features such as thrust faults — cracks in the surface where older rock is pushed above younger rock.

The scientists detailed their findings online July 1 in the journal Nature Astronomy.

Now scientists report that they may have detected thrust faults on Ceres, which suggests that the asteroid is shrinking over time, unlike icy bodies of comparable size.

"For me, the most surprising result is finding a class of tectonic features typical of terrestrial planets in a dwarf planet that is not a terrestrial planet,"  study lead author Javier Ruiz, a planetary scientist at Complutense University of Madrid, told Space.com.

The researchers analyzed images that NASA's Dawn spacecraft captured in 2015 and 2016 as it orbited about 240 miles (385 km) above the surface of Ceres. They found ridges, fractures and slopes linked with 15 possible thrust faults on Ceres that closely resemble features linked with shrinking on Mercury and Mars.

These newfound features seem more abundant in ancient terrains closer to Ceres' poles than its equator. However, the researchers cautioned that the findings might only be due to how lighting made those features easier to see.

The scientists suggested that Ceres may have shrunk as the dwarf planet's innards separated into different layers as it cooled, a bit like how Earth's interior separated into a core, mantle and crust layers over time. When Ceres was born, it was likely a porous mix of rock and ice, and as its slushy body divided into layers, empty pores would have gotten filled, leading it to contract, Ruiz said.

Future analysis of Ceres' thrust faults might "give a lot of valuable information on the nature of the crust, the proportion and nature of ices and rocks, and hence to improving our understanding of the evolution of Ceres," Ruiz said.

• Dwarf Planet Ceres: Biggest in the Asteroid Belt (Infographic)
• Dwarf Planet Ceres Hosted Near-Surface Water for Millions of Years
• A Weird Mud Plume May Have Built the Highest Peak on Dwarf Planet Ceres

Follow Charles Q. Choi on Twitter @cqchoi. Follow us on Twitter @Spacedotcom and on Facebook.

A plume of mud from the depths of dwarf planet Ceres may have created the miniature world's highest mountain, a new study reveals — marking the first time scientists have discovered such a plume in the solar system.

With a diameter of about 585 miles (940 kilometers), Ceres is both a dwarf planet and the largest member of the asteroid belt located between Mars and Jupiter. In 2015, NASA's Dawn spacecraft discovered a 2.5-mile-high (4 km) and 10.5-mile-wide (17 km) dome-shaped mountain on Ceres dubbed Ahuna Mons, which is by far the largest feature on the dwarf planet's surface.

Previous research suggested that Ahuna Mons was relatively young. Specifically, the low number of craters on the mountain suggested that it formed within the last 200 million years or so. (Like the rest of the solar system, Ceres itself formed about 4.56 billion years ago.)

Related: Photos: Dwarf Planet Ceres, the Solar System's Largest Asteroid

The shape of this dome and bright streaks of salt detected on its slopes suggested that it formed volcanically, most likely from salty fluid that erupted from the interior of Ceres. However, dwarf planets such as Ceres are expected to cool and solidify relatively quickly after their formation, and so "interior activity so late in the history of the body was not thought to be possible," study lead author Ottaviano Ruesch, a planetary geologist at the European Space and Technology Center at Noordwijk in the Netherlands, told Space.com.

To find out Ahuna Mons' origin, scientists analyzed Dawn's maps of Ceres' gravity field. The strength of the field depends on Ceres' mass, and since the dwarf planet's mass is not spread evenly, its gravitational pull is stronger in some places on the planet's surface and weaker in others. As such, gravity maps can reveal otherwise hidden details of how a world's mass is concentrated.

Previous analyses of Ceres' gravity field suggested that under a rocky crust about 24 miles thick (40 km), the dwarf planet possessed a mantle layer loaded with fluids. The new research found what appeared to be a plume of slurry from this mantle, a muddy mix of salty brine and solid particles.

This mantle plume from Ceres is unlike any other seen to date, Ruesch noted. On Earth, mantle plumes are made of molten rock, and on icy moons such as Saturn's Enceladus, mantle plumes are watery. In contrast, Ceres may possess plumes of mud.

The researchers suggested that Ceres' mantle of mud may still experience convection — that is, churning. "The possibility of mantle convection and upwelling plumes in a mud-bearing mantle was, up to now, only suggested theoretically," Ruesch said. "We now have substantial evidence that upwelling plumes exist on dwarf planets made of rock and water ice."

The scientists detailed their findings online June 10 in the journal Nature Geoscience. 

• Ceres: The Smallest and Closest Dwarf Planet
• Dwarf Planet Ceres Hosted Near-Surface Water for Millions of Years
• Giant Ice Volcanoes Once Covered Dwarf Planet Ceres

Follow Charles Q. Choi on Twitter @cqchoi. Follow us on Twitter @Spacedotcom and on Facebook. 

The football-shaped dwarf planet Haumea, which is surrounded by an almost perfectly circular ring of particles, is the most distant ringed object in the solar system. Haumea's ring is too faint to be seen from planet Earth, so astronomers have turned to context clues to find out more about these particles. 

In a new study, researchers with the São Paulo Research Foundation in Brazil have detailed the ring's size, shape and other characteristics by simulating the Haumea system on a computer. By simulating the ring's particles in different configurations around the dwarf planet and calculating which scenario would render the ring most stable, the scientists were able to infer the likely qualities of the ring without ever looking at it directly.  

“Our study isn’t observational. We did not directly observe the ring. No one ever has,” Othon Cabo Winter, an engineering professor at São Paulo State University in Guaratinguetá, Brazil, who led the new study, said in a statement. 

Related: Meet the Solar System's Dwarf Planets

Astronomers first spotted Haumea far beyond the orbit of Pluto in 2003, and it was originally classified as a Kuiper Belt Objects (KBO). The dwarf planet's two moons, Hi'iaka and Namaka, were first seen in 2005 by astronomers using the W.M. Keck Observatory in Hawaii. As astronomers began to find more objects like Haumea floating in that outer region of the solar system, the dwarf planet later became one of a handful of far-out bodies whose discovery led to Pluto being demoted from its status as the ninth planet in the solar system to the "king of the dwarf planets" in 2006. 

Although astronomers have pretty solid evidence that Haumea has a ring, no one has actually observed the ring directly. The feature is too narrow and distant to see through a ground-based telescope, and no spacecraft has ever flown by Haumea to take photos of the dwarf planet up close. Somewhat ironically, everything we know about Haumea's ring system came from an even more distant object — a bright star named URAT1 533-182543. 

In 2017, Haumea briefly passed in front of the star in what's known as a stellar occultation. By looking at how the starlight flickered during the occultation, astronomers hoped to learn more about Haumea's physical properties such as its size, shape and density. But to the researchers' surprise, they discovered the ring system, too. 

"The light from the star was observed from Earth as the star was occulted by Haumea. Its brightness decreased as Haumea passed in front of it, enabling the astronomers to obtain information about Haumea's shape," Winter said. "The star’s light also faded when the ring passed in front of it, enabling them to obtain information on the ring as well." 

After the occultation, researchers studied the light curves and determined that Haumea and its ring have an orbital resonance of 1:3, which means that in the time it takes the ring particles to complete one orbit around Haumea, the dwarf planet itself completes three full rotations. However, the new simulations suggest that in order for this to be true, the ring can't be perfectly circular. 

"Based on simulations using the available data on Haumea and the ring, subject to Newton's law of gravitation, which describes the motions of the planets, we concluded that the ring isn't in that region of space owing to the 1:3 resonance but owing to a family of stable periodic orbits," Winter said. In other words, the ring particles don't orbit the dwarf planet with a resonance of 1:3, but do orbit Haumea periodically in a slightly different path that puts them close to that 1:3 resonance. 

So, Haumea's ring is still pretty round, but it isn't as perfectly round as earlier research has suggested. And even though the ring particles appeared to be in orbital resonance with Haumea, their periodic orbits don't form a nice whole-number ratio with Haumea's orbit after all. 

The new paper describing Haumea's ring system was published Feb. 7 in the Monthly Notices of the Royal Astronomical Society.  

• Tiny Ringed Object Beyond Saturn May Reveal Secrets About Giant Planets
• Bizarre Dwarf Planet Wrapped in Ice Blanket 
• Dwarf Planet Named for Hawaiian Goddess 

Email Hanneke Weitering at hweitering@space.com or follow her @hannekescience. Follow us on Twitter @Spacedotcom and on Facebook.

The Kuiper Belt is a cold donut-shaped region of icy objects that circles the outer solar system beyond the orbit of the eighth planet from the sun, Neptune. 

It is similar to the main asteroid belt, found between Mars and Jupiter, in that its objects are comprised of material leftover from the formation of the solar system around 4.6 billion years ago, according to NASA.

The Kuiper Belt is far larger than the main asteroid belt, up to 20 times as wide and 20 to 100 times it's mass according to Nine Planets. 

Related: Why is Pluto not a planet? 

Like the main asteroid belt, the Kuiper Belt was shaped by the orbit of a giant planet. While the gas giant Jupiter fabricated the structure of the main asteroid belt, it was the orbit of Neptune that prevented material from coalescing into a large planet and thus that carved out the thin disk of the Kuiper Belt.

Humanity is only just beginning to explore the Kuiper Belt with just two spacecraft traveling out there thus far. In 1983, the Kuiper Belt region was visited by NASA's Pioneer 10 spacecraft, which crossed into the belt but didn't visit any of its worlds. It was followed by the New Horizons spacecraft which conducted an investigation of Pluto and its companion Charon in 2015 after a decade-long journey from Earth. The spacecraft went on to visit other Kuiper Belt objects including Arrokoth, the icy 'space snowman'.

NASA writes: "The Kuiper Belt is truly a frontier in space — it's a place we're still just beginning to explore and our understanding is still evolving." 

Kuiper Belt FAQs answered by an expert

We asked Dr. Samatha Lawler, an astronomer in the United States a few questions about the Kuiper Belt and objects at the edge of the solar system. 

Where is the Kuiper Belt?

NASA says that the inner edge of the doughnut-shaped Kuiper Belt begins at the orbit of Neptune and a distance of around 2.8 billion miles (4.8 billion kilometers) from the sun, with its main concentration of bodies ending at around 4.6 billion miles (7.4 billion km) from the star. 

Astronomers usually measure vast distances like this within the solar system in "Astronomical Units" (AU) with 1 AU equivalent to around 93 million miles, the average distance between the Earth and the sun.

This puts the inner of the Kuiper Belt at 30 AU from the sun and the end of its main region at about 50 AU. There is another more disordered region of the Kuiper belt called the "scattered disc" that continues out to around 1,000 AU away from the solar system's central star. Those distances mean that the Kuiper Belt is one of the largest structures in the solar system.

The Kuiper Belt may not be the most distant band of icy bodies in the solar system, however. Scientists hypothesize that even further out than the Kuiper Belt is a collection of objects called the Oort Cloud that is often confused with the Kuiper Belt.

While short-period objects are believed to originate from the Kuiper Belt, according to NASA the Oort Cloud is believed to be the source of long-period comets that take longer than 200 years to circle the sun. 

The inner edge of the Oort is believed to exist between 2,000 and 5,000 AU from the sun, while the outer edge could be 10,000 or even 100,000 AU from our star, which NASA says is one-quarter to halfway between the sun and the nearest neighboring star. 

Who discovered the Kuiper Belt?

The Kuiper Belt is named for Dutch astronomer Gerard Kuiper (1905–1973) who in 1951, proposed the existence of a disc-shaped region of icy objects beyond Neptune from which comets originate.

Prior to the work of Kuiper, the first Kuiper Belt inhabitant to be discovered was Pluto found by Clyde Tombaugh at the Lowell observatory in February 1930. This means astronomers had discovered the Kuiper Belt long before they knew about it, though finding Pluto did lead to speculation about other objects existing out past Neptune.

In 1943 Irish astronomer Kenneth Edgeworth published a paper arguing that solar system bodies and their distribution were not bounded by the orbit of Pluto, which can be seen as the genesis of the Kuiper Belt concept. Though Kuiper presented a much stronger case in favor of this idea 8 years later, many astronomers called this band of icy bodies the "Edgeworth-Kuiper" in reference to that contribution.

Confirmation of the existence of the Kuiper Belt would have to wait for another four decades. According to John Hopkins University Applied Physics Laboratory in 1992 University of Hawaii researchers Dave Jewitt and Jane Luu discovered a small body orbiting the sun beyond Neptune.

This object, the first "classical TNO (Trans-Neptunian Object)," was eventually designated 1992QB1 and triggered the discovery of thousands more Kuiper Belt Objects (KBOs). NASA points out that since the discovery of 1992QB1 astronomers have discovered over 2,000 KBOs. 

The reason it took so long to discover Kuiper Belt belt objects is that they are so small and so far away. 

Classifying Kuiper Belt objects

John Hopkins University Applied Physics Laboratory says Kuiper Belt bodies are classified as follows: 

Cold Classical KBOs (Kuiper Belt Objects) 

Cold refers not to temperature but to circular uninclined orbits. These objects are located in a band 6 AU wide between 42 and 48 AU from the sun and 3 AU.

These KBOs tend to be small, with none 500 miles across or wider. They are also redder in color than other KBOs.

The term "classical" refers to the fact these objects are on the type of obit Kuiper spoke about.

These are likely to be comprised of the original material that comprised the Kuiper Belt, unperturbed by the orbit of planets. 

Hot Classical KBOs 

"Hot" refers to the fact these KBOs have non-circular and inclined orbits.

This means these objects while usually located, at similar distances from the sun as cold classical KBOs can travel much further from the sun during their orbit.

Their sizes and colors vary, greyer than cold classicals, they also tend to be larger. They are found in a band around 12 AU thick.  

 Resonant KBOs 

These KBOs are locked into a resonant dance with Neptune. 3:2 resonants make two orbits of the sun for every 3 orbits of the ice giant.

The 2;1 resonants, sometimes called "little Plutos" because the dwarf planet is a member of this group, make one orbit for every two orbits of Neptune.

Scattered KBOs 

These KBOs possess unstable orbits, possibly because they have passed too close to Neptune and the ice giant's gravity has knocked them off-course.

These chaotic orbits can carry these bodies as far as 100s of AU away from the sun at their most distance, and closer than Neptune to the star at their closest. 

Extreme TNOs (Trans-Neptunian Objects) 

A very new grouping, there are only a few members of this category. These objects may eventually be revealed to not be part of the Kuiper belt at all as they can travel as far as 1,000 AU from the sun.  

Famous inhabitants of the Kuiper Belt

The Kuiper Belt is home to millions of rocky and icy objects referred to as either Kuiper Belt objects (KBOs) or trans-Neptunian objects (TNOs). The frigid condition of these objects is due to their vast distance from the sun. NASA says there may be trillions of icy objects in the Kuiper Belt, with hundreds of thousands of these objects having diameters larger than 62 miles (100 km). It is home to at least five known dwarf planets, Eris, Haumea, Makemake, Quaoar, and of course Pluto.

Many of these dwarf planets have their own moons and even their own faint ring systems, with scientists recently spotting a ring around Quaoar which also has its own moon Weywot. Around 80 KBOs have been discovered to have binary companions of similar sizes meaning it can't be accurately determined which is the main body and which is the moon, these are referred to as "binary KBOs."  

Kuiper Belt objects come in all shapes and sizes

The largest Kuiper Belt objects are Pluto and Eris, Pluto has a diameter of around 1,430 miles (2,380 km) while Eris's diameter is slightly larger at around 1,444 miles (2,330 km). There are as many as seven other Kuiper Belt objects known with diameters between around 600–900 miles (950–1,500 km). Only these larger KBOs are expected to have their own atmospheres. 

The smallest KBO ever seen in visible light has a diameter of just 3,200 feet and was spotted at a distance of 4.2 billion miles away, but the constant collision of these objects means the Kuiper Belt is a population by a multitude of much smaller fragments. 

KBOs can vary in color and surface reflectivity. Pluto, for example, reflects around 60% of incident sunlight that falls upon it, as a comparison Earth reflects just 10%.

Other KBOs have darker surfaces with reflectivity ranging from 20% to as low as 4%. John Hopkins University Applied Physics Laboratory suggests that the darkest of these objects could be rich in complex carbon-rich polymers. The color of Kuiper Belt objects is believed to range from dark grey to red, with this the result of a wide range of chemical compositions and their evolution though this is difficult to determine at such great distances. 

KBOs also come in a range of shapes, with arguably the most unusual being that of (486958) 2014 MU69 or Arrokoth  —  meaning "sky" in Powhatan/Algonquian language  — which  is also referred to as the "space snowman" due to its shape. 

Discovered by the New Horizons science team in 2014 using the Hubble Space Telescope, Arrokoth is double-lobed and partially flattened. The "head" and "body" of this 22 miles (35 kilometers) long, 12 miles (20 km) wide, and 6 miles (10 km) thick snowman are composed of two separate bodies that have merged into one, a so-called "contact binary." Unlike its snowman namesake, however, the object which went by the name "Ultima Thule" prior to its official naming in 2019, is extremely red in color. 

Perhaps the most infamous hypothesized tenant of the solar system is "Planet X" or "Planet 9" following the demotion of Pluto to a dwarf planet. Proposed to exist way beyond Pluto, this Neptune-sized world would have a highly elongated orbit. 

The primary line of evidence for this planet as it was proposed in 2015 is the strange elongated orbit of some smaller KBOs at the outskirts of the Kuiper Belt. This could be caused by the gravitational influence of an undiscovered massive object, though evidence beyond this has been scarce and controversial. 

The Kuiper Belt is losing weight

The Kuiper Belt as we see it today might actually be a lot more empty than it used to be. The University of California Los Angeles (UCLA) says observations of the Kuiper Belt have led to the development of the "Nice Model" which suggests that the mass now in the Kuiper Belt, around 0.1 times the mass of Earth, is too great to have grown by accretion over the age of the solar system.

This means that the Kuiper Belt may have once contained material equivalent to 10 or even 100 times the mass of Earth, 100 to 1,000 times more than the mass it has today. The loss of this mass likely occurred due to shifting in the orbits of the giant planets, Jupiter, Saturn, Uranus, and Neptune.

According to NASA as the latter two planets were forced to drift outwards by Saturn and Jupiter they bent the path of many icy objects inwards. The massive gravity of Jupiter slingshotted out to the edge of the solar system, probably forming the Oort Cloud, or out of the solar system entirely. 

NASA adds that the Kuiper Belt is still eroding today, objects there collide creating smaller collisional fragments which collide again grinding these objects to dust. This dust is then blown out of the solar system by streams of charged particles from the sun known as the solar wind.

Additional resources

The most infamous object in the Kuiper Belt is Pluto which is at the heart of a debate surrounding what should be considered a planet or what should not. The justification for downgrading Pluto to a dwarf planet, a decision made by the International Astronomical Union (IAU) in 2016, is explained here in this piece published here on the Library of Congress website. 

Even further out in the solar system than the Kuiper Belt is an icy shell of billions or even trillions of objects called the Oort Cloud. You can chill and read about in more detail with these resources from NASA.

Thus far only one spacecraft has visited the Kuiper Belt when in 2015 the New Horizons mission flew past Pluto and its moons. You can read about the mission in more detail here on the official NASA website. 

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Some parts of the dwarf planet Ceres harbored pockets of near-surface water for millions of years in the recent past, a new study suggests.

Researchers analyzed observations of Ceres' Occator Crater made by NASA's Dawn spacecraft, which studied the dwarf planet from orbit from March 2015 to October 2018, when the probe ran out of fuel. 

The 57-mile-wide (92 kilometers) Occator sports dramatic bright spots, which Dawn team members determined are salts left behind when briny water boiled away into space. This water likely began as subsurface ice, which was melted by the intense heat of the impact that created Occator about 20 million years ago. Once liquefied, some of it bubbled up to the surface via fissures and was lost. [In Pictures: The Changing Bright Spots of Dwarf Planet Ceres]

Such sublimation occurred as recently as 4 million years ago; that's the apparent age of the youngest deposits on Occator's floor. And that 16-million-year gap is puzzling, researchers said.

"It’s difficult to maintain liquid so close to the surface," study co-author Julie Castillo-Rogez, a planetary scientist at NASA’s Jet Propulsion Laboratory (JPL)  in Pasadena, California, said in a statement. Indeed, previous research has estimated that "cryomagma" could stay liquid in Occator's near subsurface for just 400,000 years or so.

But the new study provides at least a partial answer. Modeling work by Castillo-Rogez and study lead author Marc Hesse, an associate professor at the University of Texas' Jackson School of Geosciences, suggest that Occator's near subsurface contains insulating materials, which could have kept the "cryomagma" liquid for about 10 million years.

"Now that we're accounting for all these negative feedbacks on cooling — the fact that you release latent heat, the fact that as you warm up the crust it becomes less conductive — you can begin to argue that if the ages are just off by a few million years, you might get it," Hesse said in the same statement.

"They used more up-to-date data to create their model,” said JPL planetary geologist Jennifer Scully, who was not involved in the new research. "This will help in the future to see if all of the material involved in the observed deposits can be explained by the impact, or does this require a connection to a deeper source of material. It’s a great step in the right direction of answering that question."

The new study was published in December in the journal Geophysical Research Letters.

The Dawn spacecraft enjoyed a long and very productive life. Before its work at the 590-mile-wide (950 km) Ceres, Dawn orbited the protoplanet Vesta, which is about 330 miles (530 km) wide. Vesta and Ceres — the two largest objects in the asteroid belt between Mars and Jupiter — are considered leftovers from the solar system's planet-formation days, and Dawn's mission was designed to help shed light on this mysterious, long-ago epoch (hence the name, which is not an acronym).

Dawn was the first probe ever to orbit a dwarf planet, and the first to circle two celestial bodies beyond the Earth-moon system.

Mike Wall's book about the search for alien life, "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate) is out now. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or on Facebook. 

Nearly three years since NASA's Dawn mission arrived at Ceres, the spacecraft has run out of fuel. Is it time to start thinking about sending another mission to the dwarf planet?

The $467 million Dawn spacecraft launched in 2007 on a mission to study the two largest objects in the asteroid belt, Vesta and Ceres. After studying the asteroid Vesta from orbit for about a year, it moved on to Ceres, the smallest dwarf planet in the solar system and the largest space rock orbiting in the asteroid belt.

While in orbit at Ceres, Dawn discovered that the dwarf planet sports hundreds of weird bright spots, contains plenty of water ice and has organic molecules (the basic building blocks for life) on its surface. By the mission's end, however, scientists were still left with some big questions about Ceres and what it can teach us about the possibilities of life beyond Earth — questions that could be answered with a follow-up trip to the surface. [Photos: Asteroid Vesta and NASA's Dawn Spacecraft] 

"I think the kinds of questions that we are going to be left with will probably require going down to the surface, because there's only so much you can tell from orbit," Paul Schenk, a participating scientist for the Dawn mission with the Universities Space Research Association at the Lunar and Planetary Institute in Houston, told Space.com.

Specifically, Schenk said he would like to see a mission sent to explore Occator Crater, a 57-mile-wide (92 kilometers) crater containing the biggest and brightest of Ceres' spots. Like the other bright spots on Ceres, Occator Crater contains salty deposits that were left behind when briny water sprayed up from underground and then froze on the surface. This discovery by the Dawn mission revealed that the interior of Ceres is warmer than scientists previously thought. In the case of Occator Crater, a recent impact was likely the source of that heat, Schenk said. 

The most prevalent mineral at Occator Crater is sodium carbonate, which also happens to be prevalent in places on Earth that show hydrothermal activity — places like Yellowstone National Park "where certain types of bacteria are known to thrive," Schenk said. However, he said that it's "rather unlikely" that microbial life exists on Ceres, because the heat generated from impacts doesn't last long enough for life to evolve. "The impact generates enough heat to melt the ice and create the groundwaters that can then circulate in a central area," he said, but "the zone of heat contracts until the water goes away and freezes up" over the course of tens of thousands to a few million years. Here on Earth, the earliest forms of life arose 700 million years after the Earth formed.

Regardless of whether Ceres is capable of hosting life — a possibility that scientists have neither ruled out nor confirmed at this point — the hydrothermal processes seen on the dwarf planet could help scientists understand similar processes on other bodies in the solar system, like Jupiter's moon Europa or Saturn's moon Enceladus — two of the top contenders for hosting possible life beyond Earth. Features resembling dried-up hydrothermal vents on Mars could also have sustained life sometime in the planet's history. Like the bacteria that live in deep-sea hydrothermal vents on Earth, organisms living in similar geological features on other world don't need sunlight to survive. Instead, they would rely on geothermal energy, like hydrothermal vents and plate tectonics.

In the case of Ceres, getting hit with other large space rocks appears to be the source of its geothermal energy. "Hydrothermal reactions with the water are clearly bringing up minerals to the surface," Schenk said. "In order to understand how that process works on other planets, including Mars, going back and understanding that chemistry and that physics — the physical process of what actually happens, how those materials delivered to the surface and what reactions are taking take place — are going to be important to understanding hydrothermal processes throughout the solar system. We have a lot of that information here on Earth, but the chemistry of Earth's crust is very different than it is on Ceres."

Landing and roving on Ceres

Because Occator Crater holds some tantalizing clues about the conditions necessary for life to arise on other worlds, scientists are hoping to send a lander to further explore Ceres' most fascinating feature, Schenk said. Ideally, any future missions would involve a small rover like the ones that landed on the asteroid Ryugu in September.

"It would have to be able to take some instruments that can tell you some diagnostic information about the composition, so it would have to survive the landing, and it probably would need to be able to move around to get to the specific site of interest, because you have to land safely but then you have to go to the area that's interesting, which could be complicated," Schenk said. (For example, Japan's Hayabusa2 mission to Ryugu has had a difficult time finding a safe landing site on the asteroid's surprisingly rocky surface.)

While Dawn could only study Ceres from orbit, reaching a closest altitude of 22 miles (35 km), a spacecraft on the surface could learn more about the dwarf planet's composition by scooping a sample and analyzing it in situ, or inside the spacecraft itself. Dawn used spectrometers to determine what elements are on the dwarf planet's surface, but those measurements are "dominated by those materials that are spectrally active, those that reveal absorption bands at particular wavelengths," and carbonaceous materials don't show up well in those measurements, Schenk said. "Carbonaceous materials often are pretty bland, so we probably have to go down to the surface to find it." 

Scientists have been working on preliminary plans for the next mission to Ceres since as early as 2008, or seven years before Dawn would become the first spacecraft to visit the dwarf planet. A proposed mission called the Ceres Polar Lander would send an orbiter-lander combo to Ceres, dropping the lander at its north pole to search for clues about life. The mission would use the same kind of soft-landing techniques NASA has used to land spacecraft on Mars.

A team of researchers with the European aerospace manufacturing company Thales Alenia Space and the University of Nantes in France presented the Ceres Polar Lander mission concept at the European Planetary Science Congress in 2008.

When the Ceres Polar Lander was first proposed, scientists thought that Ceres' north pole would be the most interesting place to study. However, this was long before Dawn discovered Occator Crater, which is now arguably the most interesting place on Ceres.

Currently, no space agencies have plans to send another mission to Ceres, but that could change now that the Dawn mission has ended. Any proposed NASA missions will have to go through a lengthy review process before they can be selected to go to Ceres, but in the meantime, scientists have plenty of data from Dawn to sift through, Schenk said. "We're only starting to understand Ceres … it's going to take a while to figure out what we're actually seeing."

Email Hanneke Weitering at hweitering@space.com or follow her @hannekescience. Follow us on Twitter @Spacedotcom and on Facebook. Original article on Space.com.

Imagine Earth's north pole drifting as far south as Ireland — that is about how much the crust of the dwarf planet Ceres has wandered over the rest of that miniature world over time, a new study finds.

With a diameter of about 585 miles (940 km), Ceres is by far the largest member of the asteroid belt located between Mars and Jupiter. Previous research suggests that Ceres might possess a frozen crust, an icy feature it has in common with a number of worlds in the solar system, such as Jupiter's moon Europa, Saturn's moon Titan, and fellow dwarf planet Pluto.

To learn more about Ceres' frozen nature, study author Pasquale Tricarico, a senior scientist at the Planetary Science Institute in Tucson, Arizona, investigated data from NASA's Dawn space mission, which began orbiting Ceres in 2015. He focused on the shape of the dwarf planet as well as minute variations in the strength of its gravitational pull over its surface, which together shed light on how the density varies across the giant asteroid's crust. [Amazing Photos of the Dwarf Planet Ceres]

Ceres' wandering skin

The scientist discovered a number of anomalies that suggested Ceres experienced "true polar wander," which is when the entire solid outermost part of a world is able to drift over the rest of it because they experience different rates of spin. To envision this, imagine that a peach's skin became detached from the fruit's meat and pit and was free to move about over it.

"I don't think it was speculated until now that Ceres experienced true polar wander," Tricarico told Space.com.

One possible sign of true polar wander on Ceres is a giant ridge encircling the dwarf planet tilted at a 36-degree angle from the present equator. Tricarico suggested this may be where the equator of Ceres once was.

"The shape of a body tends to bulge at its equator, which can stress the crust there and leave fractures, which is what we think we see," Tricarico said.

This ridge and other anomalies on the surface of Ceres suggest that in the past, the dwarf planet's equator was tilted 36 degrees from where it lies now. In comparison, such a tilt is great enough to place Earth's north pole as far south as the spa town of Harrogate in northern England.

A familiar cosmic tale

Previous research suggested that several planets and moons in the solar system experienced true polar wander, including Earth and Mars.

This reorienting may occur due to how mass is scattered across their exteriors and changes in their rates of spin — for example, prior work suggested Mars experienced true polar wander to move its massive Tharsis volcanic region to a more stable position nearer the Red Planet's equator. Ceres may also possess large differences in density across its crust, which potentially helped drive true polar wonder on it to help its exterior and interior experience similar rates of spin.

In addition, if one looks at where the area marking the north pole of Ceres was and where that point is now, "the path it took does not look straight, but it followed an S-shaped path instead," Tricarico said. "It will be interesting to study why that was, and to connect that with the mechanism that triggered the true polar wander and what that all tells us about the interior dynamics of Ceres."

Future research can also examine the potential causes of density anomalies on Ceres. One such anomaly seems located in a large crater on a dwarf planet, which might be the remnants of a plume of material rising from the mantle to the crust that lasted hundreds of millions of years, Tricarico said.

Tricarico detailed his findings online Oct. 8 in the journal Nature Geoscience.

Follow Charles Q. Choi on Twitter @cqchoi. Follow us @Spacedotcom, Facebook and Google+. Original story on Space.com. 

NASA's New Horizons spacecraft successfully completed a brief engine burn on Oct. 3, the first maneuver in which it was able to rely on actual photographs it had already taken of its eventual target.

According to a NASA statement about the engine burn, it was successful and sped the spacecraft up by 4.6 mph (2.1 m/s). At the time, the spacecraft was about 3.95 billion miles (6.35 billion kilometers) away from Earth, temptingly close to its next destination.

That target is a Kuiper Belt object called 2014 MU69 and nicknamed Ultima Thule, which is about 4.1 billion miles (6.6 billion kilometers) away from Earth. In mid-August, the spacecraft was able to take its first image of the object, and its images now help the spacecraft's trajectory team design the small path corrections that will help it reach its target.

"Thanks to this maneuver, we're right down the middle of the pike and on time for the farthest exploration of worlds in history — more than a billion miles beyond Pluto," mission principal investigator Alan Stern, a planetary scientist at the Southwest Research Institute, said in the statement. "It almost sounds like science fiction, but it's not. Go New Horizons!"

The flyby is currently scheduled for 12:33 a.m. ET on Jan. 1, 2019, which will still be Dec. 31 in the rest of the U.S. As the flyby approaches, that time estimate will be honed ever more precisely, an important step in ensuring the maneuver's success.

"Since we are flying very fast and close to the surface of Ultima, approximately four times closer than the Pluto flyby in July 2015, the timing of the flyby must be very accurate," Derek Nelson, New Horizons optical navigation lead, said in the statement. "These first images give us confidence that Ultima is where we expected it to be, and the timing of the flyby will be accurate."

Email Meghan Bartels at mbartels@space.com or follow her @meghanbartels. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

Dozens of ancient ice volcanoes once dotted the surface of the dwarf planet Ceres, a new study finds.

Whereas regular volcanoes on Earth erupt with molten rock, ice volcanoes — which are also known as cryovolcanoes — spew out plumes of water-ice and other frozen molecules. Previous research has detected traces of cryovolcanism on several bodies in the outer solar system, such as Saturn's moon Enceladus and Pluto. However, much remains unknown about cryovulcanism, especially compared with regular volcanism.

In 2015, NASA's Dawn spacecraft discovered a 2.5-mile-high (4 kilometers), dome-shaped cryovolcano dubbed Ahuna Mons on Ceres. With a diameter of about 585 miles (940 km), Ceres is the largest member of the asteroid belt located between Mars and Jupiter. [Dwarf Planet Ceres' Bizarre Bright Spots Shine in Stunning Up-Close View]

"Ceres is the only cryovolcanic body we've orbited with a spacecraft," study lead author Michael Sori, a planetary scientist at the University of Arizona at Tucson, told Space.com. "This is the best opportunity we've had so far to learn more about the similarities and differences between cryovolcanism and regular volcanism."

Based on the number and size of meteor craters that Ahuna Mons has engulfed and the estimated rate of meteor strikes that Ceres has experienced, prior work suggested that Ahuna Mons is at most 240 million years old. (Like the rest of the solar system, Ceres itself formed about 4.56 billion years ago.)

Ahuna Mons is the only prominent cryovolcano that scientists have spotted on Ceres. This is odd: If the interior of Ceres were still warm enough to have a cryovolcano, then it should have generated cryovolcanoes in the past, when it was warmer, and evidence of those cryovolcanoes should dot the dwarf planet's surface today.

Sori and his colleagues reasoned that cryovolcano domes gradually settle down, ultimately blending in with the surrounding landscape. To find this hidden evidence of ancient cryovolcanoes, they compared images from Dawn with computer models of slumped domes.

The scientists identified 22 former cryovolcanoes on Ceres, ranging from 10 to 53.4 miles (16 to 86 km) wide and 0.7 to 2.7 miles (1.1 to 4.4 km) high. After estimating the ages of these features, they suggest that new cryovolcanoes have appeared on Ceres about every million years, on average, in the past billion years.

All in all, the researchers estimated the amount of icy material that has erupted onto the surface of Ceres is 100 to 100,000 times less than the amount of molten rock that has erupted on Earth, the moon, Venus or Mars. Whereas cryovolcanoes on Ceres generate an average of more than 13,000 cubic yards (9,940 cubic meters) of material each year — enough to fill a movie theater or four Olympic-size swimming pools — volcanoes on Earth generate an average of more than 1 billion cubic yards (765 million cubic m) of rock a year, according to the statement.

As such, while cryovolcanism helped shape Ceres, "it's nowhere near as dominant a process on Ceres as rocky volcanism has been on the geology of Earth, the moon, Mars and Venus," Sori said. "The dark spots you see on the moon at night are huge volcanic plains, and we don't see anything analogous like that on Ceres."

Future research can investigate other icy bodies to see if cryovolcanism plays a similar role on those worlds, Sori said. "I'm most looking forward to the 2020s, when we'll be launching missions to Europa, an icy moon of Jupiter," Sori said.

The scientists detailed their findings online Sept. 17 in the journal Nature Astronomy.

Follow Charles Q. Choi on Twitter @cqchoi. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

You may have seen the bizarre bright spots speckling the dwarf planet Ceres — but not like this.

NASA's Ceres-orbiting Dawn spacecraft has captured jaw-dropping new photos of several of the bright-white features, formally known as faculae, that lie at the bottom of the dwarf planet's 57-mile-wide (92 kilometers) Occator Crater. 

Dawn snapped the images from an elevation of about 21 miles (34 km) — just three times higher than a commercial airliner flies, NASA officials said. [In Pictures: The Changing Bright Spots of Dwarf Planet Ceres]

"The new images of Occator Crater and the surrounding areas have exceeded expectations, revealing beautiful, alien landscapes," Dawn principal investigator Carol Raymond, of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, said in a statement yesterday (July 16). 

The $467 million Dawn mission launched in September 2007 with a bold goal: to orbit and study the two largest bodies in the asteroid belt: Vesta and Ceres. Both objects are considered leftovers from the solar system's planet-formation period (hence the mission's name). 

Dawn reached Vesta in July 2011 and eyed the object up close for more than a year, finally leaving for Ceres in September 2012. 

Dawn discovered the Occator Crater bright spots during its approach to Ceres in early 2015, and later found a number of other crater-associated faculae around the dwarf planet. The probe's observations have since revealed that the bright spots are salty deposits, composed primarily of sodium carbonate and ammonium chloride.

Scientists think this material was left behind when briny water boiled away into space, but they're not sure where, exactly, those brines came from — specifically, how deep underground the reservoirs were.

Dawn team members are using the probe's observations to tackle this and other questions about the 590-mile-wide (950 km) Ceres. Some of the most intriguing data and eye-popping photos come from Dawn's most recent mission phase, during which the probe has circled above Ceres at an altitude of just 21 miles or so.

Dawn spiraled down to this superlow orbit early last month and will remain there through the end of its operational life, which is expected to come in a few months. The spacecraft is nearly out of hydrazine, the fuel that powers Dawn's small orientation-controlling thrusters. When the hydrazine is gone, Dawn will be unable to point its science instruments at Ceres, or its communications gear at Earth.

The Dawn team is presenting the results from the latest (low-orbit) mission phase this week at the Committee on Space Research conference in Pasadena.

Follow Mike Wall on Twitter @michaeldwall and Google+. Follow us @Spacedotcom, Facebook or Google+. Originally published on Space.com.

New research showcasing the dramatic topography of Pluto and its moon Charon should help scientists better guess what forces have shaped them.

The New Horizons spacecraft flew past the two bodies almost three years ago, but scientists are still exploring the wealth of data the mission produced. In the case of the new maps, that means stitching together images taken by a pair of cameras

"This was one of the most complex yet most exciting planetary mapping projects I've had the pleasure to be involved with," Paul Schenk, a planetary geologist at Universities Space Research Association's Lunar and Planetary Institute in Texas, said in a statement. "Every time new images came down, something new would be revealed."

The mapping project shows off the dramatic topography of both bodies and offers more accurate measurements of some of their most stunning features.

For example, the research has confirmed that the Tenzing Montes are the highest peaks on Pluto, boasting heights up to 3.7 miles (6 kilometers) above the nearby surface. That's the equivalent of Alaska's Denali mountain here on Earth, according to the team. It's also high enough that the scientists are more confident than ever that Pluto's surface is made of water ice — methane ice, for example, wouldn't be strong enough to hold up features that large.

Elsewhere on Pluto, the team identified possible locations where volcanic activity has shaped the dwarf planet's surface as well as a deep gash running more than 1,800 miles (3,000 km) around it, which scientists think shows the dwarf planet somehow extensively fractured earlier in its life.

The map of Charon shows an even more dramatic range of features, with even higher peaks countered by an abyss deeper than the lowest point on Earth. 

Because the process took advantage of the sun illuminating the harsh terrain, scientists have only been able to piece together the surfaces of Pluto and Charon that New Horizons flew over during their daytime — about 78 percent of Pluto and 45 percent of Charon.

That means both bodies are still hiding some secrets for their next robotic visitors, according to New Horizons principal investigator Alan Stern, a planetary scientist at the Southwest Research Institute in Texas.

"I can’t wait to see the other side of Pluto revealed in detail by a future mission to orbit the planet," Stern said in the statement.

The new work was detailed June 11 and July 3 in a pair of articles published in the journal Icarus.

Email Meghan Bartels at mbartels@space.com or follow her @meghanbartels. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

NASA's Dawn spacecraft has gotten its best-ever looks at the weird bright spots that speckle the dwarf planet Ceres.

Early last month, Dawn maneuvered its way to a new orbit around Ceres, an elliptical path that takes the probe within a mere 21 miles (34 kilometers) of the dwarf planet on nearest approach. That's more than 10 times closer than Dawn had gotten previously during its three-plus years at Ceres. 

The views from this low altitude are amazing, as some newly released imagery of the 57-mile-wide (92 km) Occator Crater shows. [In Pictures: The Changing Bright Spots of Dwarf Planet Ceres]

Occator's floor hosts odd bright deposits, which Dawn discovered during its approach to Ceres in early 2015. Subsequent observations by the probe revealed that the bright stuff, which also occurs at several other locations around Ceres, consists of sodium carbonate. 

Scientists think this material was left behind when salty water boiled away into space. But it's unclear where exactly that water came from. Was it concentrated in reservoirs near the surface? Or did it snake up to the surface via fissures from deep underground?

The newly released photos of Occator, which Dawn captured on June 14 and 22, could shed light on this mystery by painting a more complete picture of the crater floor, mission team members said.

"Acquiring these spectacular pictures has been one of the greatest challenges in Dawn's extraordinary extraterrestrial expedition, and the results are better than we had ever hoped," Dawn chief engineer and project manager Marc Rayman, of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, said in a statement. "Dawn is like a master artist, adding rich details to the otherworldly beauty in its intimate portrait of Ceres."

The $467 million Dawn mission launched in September 2007 with an ambitious goal: to orbit and study Vesta and Ceres, the two biggest objects in the main asteroid belt between Mars and Jupiter. Vesta and Ceres — which are 330 miles (530 km) and 590 miles (950 km) wide, respectively — are building blocks left over from the solar system's planet-formation period, which explains the mission's name.

Dawn orbited Vesta from July 2011 through September 2012, when it departed for Ceres. The probe arrived at the dwarf planet in March 2015, becoming the first spacecraft ever to orbit two objects beyond the Earth-moon system.

Dawn's storied mission is nearing the end; last week, the spacecraft fired its superefficient ion engine for likely the final time. Dawn is low on hydrazine, the fuel that powers the probe's smaller, orientation-controlling thrusters. When the hydrazine runs out in September or thereabouts, Dawn will be done; it won't be able to point its scientific instruments at Ceres or its antenna toward Earth to communicate.

"The first views of Ceres obtained by Dawn beckoned us with a single, blinding bright spot," Dawn principal investigator Carol Raymond, also of JPL, said in the same statement. "Unraveling the nature and history of this fascinating dwarf planet during the course of Dawn's extended stay at Ceres has been thrilling, and it is especially fitting that Dawn's last act will provide rich new data sets to test those theories."

Follow Mike Wall on Twitter @michaeldwall and Google+. Follow us @Spacedotcom, Facebook or Google+. Originally published on Space.com.

On the dwarf planet Ceres, organic molecules are more abundant than scientists originally suspected.

Last year, NASA's Dawn spacecraft detected organics, or carbon-based compounds, on the surface of Ceres. The exciting discovery raised the possibility that Ceres might be habitable and even that life could have once existed on the rocky world. And now, a new analysis of the mission data suggests that the patches on the surface of Ceres shown to contain organic material likely harbor even more of those molecules than researchers first thought.

This new analysis not only details the organic abundance; it also raises additional questions, like where the organic molecules came from, according to a statement. And the findingcould serve as a valuable template and resource for future missions to study organics on the surface of Ceres, the statement said. [Photos: Dwarf Planet Ceres: The Largest Asteroid in Photos]

It is important to note that the presence of organic molecules doesn't mean that life exists or ever existed on a world. Geological process on the surface, or even meteorite impacts, could create or deposit organics on a dwarf planet like Ceres. But scientists are still working to find the origins of these organics.

Researchers first discovered organics on Ceres using the Visible and Infrared (VIR) Spectrometer aboard Dawn. By comparing the VIR data with the wavelengths of light released by organic material on Earth, researchers first surmised that about 6 to 10 percent of the signatures on Ceres could be attributed to organic material.

In this new analysis, "We estimate that as much as 40 to 50 percent of the spectral signal we see on Ceres is explained by organics," Hannah Kaplan, lead author on the new work, said in the statement. Kaplan led the research as a graduate student at Brown University in Providence, Rhode Island, and is now a postdoctoral researcher at the Southwest Research Institute in Texas. This prediction is a drastic difference from the 6 to 10 percent previously estimated.

Researchers came to this new conclusion by comparing the VIR data collected by the Dawn spacecraft with data on organics that came from space— ones that fell to Earth in meteorites.

The researchers used extraterrestrial data for comparison as opposed to signatures from material formed on Earth because they felt the meteorite data was a closer analogue, the statement said.

This new analysis of NASA's Dawn spacecraft shows that "you can get really different results depending upon the type of organic material you use to compare with and interpret the Ceres data," Kaplan said.

These findings are "important not only for Ceres, but also for missions that will soon explore asteroidsthat may also contain organic material," she added.

This work was detailed May 21 in the journal Geophysical Research Letters.

Email Chelsea Gohd at cgohd@space.comor follow her @chelsea_gohd. Follow us @Spacedotcom,Facebookand Google+. Original article on Space.com.

A NASA spacecraft is about to get up close and personal with Ceres, a giant asteroid that also happens to be the only dwarf planet in the inner solar system. 

This month, NASA's Dawn spacecraft will shift into an orbit that will skim just 22 miles (35 kilometers) above Ceres at its closest point, allowing Dawn to get its best views yet of the dwarf planet. At its farthest point, the new elliptical orbit will carry Dawn out 2,500 miles (4,000 kilometers).

"The team is eagerly awaiting the detailed composition and high-resolution imaging from the new, up-close examination," Carol Raymond, principal investigator for the Dawn mission at NASA's Jet Propulsion Laboratory, said in a statement. "These new high-resolution data allow us to test theories formulated from the previous data sets and discover new features of this fascinating dwarf planet." [See Dawn's Amazing Photos of Dwarf Planet Ceres]

One target on Ceres is especially tantalizing during the new, lower orbit. That's Occator Crater, a place with strange, bright white spots. 

"As a bonus objective, scientists would like to study the elements in one of their favorite places (and perhaps one of yours as well): Occator Crater, site of the highly reflective salt deposits, famous not only on Ceres but also on Earth and everywhere else that readers follow Dawn's discoveries," Marc Rayman, mission director and chief engineer for Dawn at JPL, wrote in an April 29 blog post. "Studying this one crater and the area around it (together known as a geological unit) could reveal more about the complex geology there."

At its lowest point, Dawn will be 10 times closer to Ceres than the probe has ever been. In fact, Rayman said it will be the closest Dawn has been to an object in the solar system since it launched from Earth.

"The last time it was that close to a solar system body was when it rode a rocket from Cape Canaveral over the Atlantic Ocean more than a decade ago," he said. 

In addition to photos, Dawn will use its instruments to understand the chemical composition of the top layer of Ceres' surface. 

The Dawn spacecraft has been orbiting Ceres in the asteroid belt (between the orbits of Mars and Jupiter) since March 2015. NASA launched the mission in 2007, sending Dawn first to the large asteroid Vesta — the second largest object in the asteroid belt after Ceres — before moving on to Ceres itself. Dawn is equipped with a fuel-efficient ion drive that allowed it to fly between asteroids.

In 2016, the probe went into a high orbit above Ceres to study the dwarf planet from a distance that ranged between 2,800 miles (4,400 km) and 24,300 miles (39,100 km). Dawn spent much of the last year in that orbit and began lowering its path around Ceres on April 16 of this year, Rayman said.

Finding an orbit that would both get close to Ceres and allow for good science observations was a challenge for mission engineers, NASA officials said. Engineers ran through more than 45,000 potential variations before hitting on one that worked. 

NASA's $466 million Dawn mission is in its second extended phase and will end its days in orbit around Ceres. After launching in 2007, the spacecraft headed to Vesta and spent a year orbiting that asteroid (from 2011 to 2012).

Email Tariq Malik at tmalik@space.com or follow him @tariqjmalik. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

Ceres is the closest dwarf planet to Earth and the largest object in the main asteroid belt between Mars and Jupiter. 

Since its discovery in 1801, Ceres has had multiple identities. First, it was thought to be a planet. Then, when it became apparent that it was too small, it was reclassified as an asteroid — the first to be discovered. In 2006, Ceres was named a dwarf planet in response to the discovery of another object, Eris, that called into question how we define planets and smaller objects such as asteroids and Kuiper Belt objects.

Whatever we call it, Ceres is a ball of rock and ice with a diameter of 592 miles (953 kilometers). It is the largest object orbiting the sun in the asteroid belt between Mars and Jupiter.

Related: What is a dwarf planet?

Ceres FAQs

Who discovered Ceres?

In the late 18th century, astronomers became convinced that there was another planet between Mars and Jupiter. They deduced this based on the Titius-Bode law, named after 18th-century German astronomers Johann Daniel Titius and Johann Elert Bode, which describes an apparent pattern in the spacing of the orbits of the solar system planets. It predicted that there should be a planet in the wide gap between Mars and Jupiter.

So a group of European astronomers, calling themselves the "celestial police," set about finding this planet. But they were beaten by Italian astronomer Giuseppe Piazzi, who was not initially a member of their group when he discovered Ceres. It was thought that the problem had been solved. 

But soon enough, more objects were discovered between Mars and Jupiter: Pallas was spotted in 1802, Juno in 1804 and Vesta in 1807. They couldn't all be planets. Indeed, they seemed too small; unlike Mars and Jupiter, they were unresolvable in a telescope. Instead, they represented a new class of objects: asteroids.

In the centuries since, over a million asteroids have been discovered in this region, called the main asteroid belt. Ceres is the largest of them, by far. The next largest, Vesta, is 330 miles (530 km) across.

What is Ceres named after?

Back in the 18th and 19th centuries, astronomers often wanted to name the objects they discovered after their patrons. For example, William Herschel initially tried to name Uranus "Georgium Sidus" after King George III. However, astronomers outside the United Kingdom frowned upon that name. 

Similarly, when Piazzi discovered Ceres, he wanted to name it "Ceres Ferdinandea," after King Ferdinand of Sicily, who had founded the observatory in Palermo from which Piazzi discovered Ceres. The reference to royalty was dropped, but the name Ceres,  the Roman goddess of agriculture and fertility, remained.

Where is Ceres?

Ceres orbits the sun between the orbits of Mars and Jupiter. Its elliptical orbit puts the dwarf planet between 2.55 astronomical units (AU), or 237 million (381 million km), from the sun at its closest point (perihelion) and 2.98 AU, or 277 million miles (446 million km) from the sun at its farthest point (aphelion). 

Ceres takes 4.6 Earth years, or 1,682 Earth days, to orbit the sun, according to NASA. Days on Ceres are much shorter than on Earth, with Ceres spinning on its axis once every nine hours.

What is it like on Ceres?

Living on Ceres would not be fun. The dwarf planet has no atmosphere, so you'd need to wear a spacesuit. This would not only provide you with air to breathe but also protect you from the freezing temperatures, which, on Ceres' day side, range from minus 136 to minus 28 degrees Fahrenheit (minus 93 to 33 degrees Celsius). Nighttime temperatures are around 225 F (minus 143 C).

On the plus side, you'd feel like you'd lost a lot of weight. The gravity is only 0.2 to 0.3 meters per square second or about 3% of that on Earth. That means that if you weighed 150 pounds (68 kilograms) on Earth, you'd feel like you weighed 4.5 pounds (2.04 kg) on Ceres.

How does Ceres compare to the other dwarf planets?

Ceres is the closest dwarf planet to Earth. All of the other dwarf planets in the solar system are very far away, in the Kuiper Belt beyond Neptune.

Ceres has some similarities with the other dwarf planets, such as Pluto and Eris. It is rubble left over from the formation of the solar system — a protoplanet that was stillborn and never grew any further. 

However, Ceres differs in its composition: Ceres is mostly rocky, whereas Pluto and its neighbors are mostly icy.

Ceres does have some ice, however. Its overall density is only about 2 to 2.3 grams per cubic centimeter, which is too low to be all rock. This implies that a quarter of Ceres is made of ice, mixed in with the surface regolith and in layers beneath the surface.

Dawn spacecraft's visit to Ceres

In 2015, NASA's Dawn spacecraft, having already visited Vesta, traveled to Ceres. As Dawn approached Ceres, it imaged a bright spot on the surface, which, as Dawn neared, resolved into bright patches, called Cerealia Facula and Vinalia Faculae. Upon closer inspection, hundreds of bright patches have been observed on Ceres. Planetary scientists were puzzled by this. Could the bright areas be patches of exposed ice?

When Dawn arrived in orbit around Ceres and took high-resolution images of the bright spots, the largest area of white deposits was found within a 57-mile-wide (92 km) crater called Occator. These spots are not ice, though. Instead, they are mostly sodium carbonate left behind by briny water that gurgled up to the surface and sublimated, leaving behind sodium carbonate deposits.

How can water exist on such a large, airless object? Data from the Dawn mission suggests that the briny water originates from a reservoir 25 miles (40 km) beneath the cratered surface and that the sodium carbonate was first left behind on the surface within the past 9 million years as cryovolcanism brought slushy liquid to the surface. The process seems to be ongoing — Dawn detected water still in the sodium carbonate sediments, and since water should sublimate quickly when exposed to the vacuum of space, the water must be being replenished for Dawn to have detected it.

The extent of this underground water is uncertain. If we could slice Ceres in half, we would find that it is "differentiated." This means that when it formed, its interior was warm enough to separate into different layers, with the densest material sinking to the core. Ceres' core is, therefore, formed from rocks and clays. Above this large core is the briny water-ice layer, which extends 60 miles (100 km) below the surface), and possibly even deeper. The external layer is a 25-mile-thick crust of regolith, salty minerals and ice.

Is there life on Ceres?

The possibility of life on Ceres seems unlikely, given the high salt levels and low temperature. Because of the presence of water, however, it cannot be ruled out. 

Alternatively, life may have existed there in the past, when Ceres was warmer. Planetary scientists have called for Ceres to be treated as an ocean world and placed on a par with the likes of Jupiter's moon Europa and Saturn's moon Enceladus as having interest for astrobiologists. To that end, the 2023 Planetary Science Decadal Survey has suggested that a sample-return mission from Ceres should be a top priority. If anything does live on Ceres, it would be very simple microbes, according to NASA. 

Ceres expert Q&A

 We spoke with Andreas Nathues, a scientist at the Max Planck Institute for Solar System Research in Germany, about the curious nature of Ceres' bright patches and the inference that they come from a water layer deep beneath the dwarf planet's surface.

Additional resources

This infographic from NASA's Jet Propulsion Laboratory shows the five official dwarf planets: Ceres, Pluto, Eris, Makemake and Haumea. You can also find out more about them from this article from The Planetary Society.

NASA's Dawn mission is the only spacecraft that has visited Ceres. You can learn more about the Dawn mission on NASA's Dawn mission website.

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Growing patches of ice and minerals associated with liquid water reveal that the dwarf planet Ceres is still evolving.

Researchers studying the warmer region of Ceres — the largest object in the asteroid belt between Mars and Jupiter — have noticed that a patch of ice has grown larger over time. In addition, a separate team found carbon-rich minerals on Ceres' surface that do not last long . Together, the new discoveries suggest that water still has a powerful presence on the tiny world.

Using NASA's Dawn spacecraft, the researchers studied the surface of the dwarf planet. The first team, led by Andrea Raponi, of the Italian National Institute for Astrophysics (INAF), found a growing patch of ice on Juling Crater, found in the midlatitudes. They suspect that water from the crater floor is condensing on the wall, causing a patch of ice to grow larger. [7 Strange Facts About Dwarf Planet Ceres]

The second team, led by Filippo Giacomo Carrozzo, also of INAF, surveyed the carbon-rich minerals on the dwarf planet and mapped several regions in detail, revealing changes in the soil that they suspect are tied to the carbonates. The water-rich, or hydrated, minerals suggest that water has risen to the surface and boiled off, leaving the carbonates behind to reveal its presence.

"The same process can be at work in the crater floor of Juling, providing a replenishment of water under the soil that sublimates and in part condenses on the cold wall," Raponi told Space.com by email.

"The two works show that water is currently available on the surface of Ceres and produces geological and mineralogical changes on its surface," he said.

Fingerprints of water

Ceres is classified as both a dwarf planet and an asteroid. When the Dawn spacecraft arrived at Ceres in 2015, it found a nearly featureless world with a rocky surface. A single mountain, Ahuna Mons, rose from the surface. Bright spots within craters were the only color variations on the otherwise dull, gray world.

As scientists probed the dwarf planet, they found hints that Ahuna Mons was not just a mountain, but a cryovolcano — also known as an ice volcano. Thick water ice may have risen to the surface in the past, flooding the plains with ice lava. Researchers found hints that other icy cryovolcanoes may have dotted Ceres in the past before slowly easing back into the landscape, their heights spreading outward across the landscape.

Eventually, Dawn revealed that the 130 bright patches contained sodium carbonates, salts that forms on Earth as water evaporates from a body of water like a lake, or in hot springs. It's hard for water to stick around on Ceres' surface. The lack of atmosphere on the tiny world means that sunlight causes the liquid to boil away immediately, leaving behind the rest of the minerals carried with it to the surface — such as carbonates.

"Carbonates are minerals that are very important because they can give us information about the presence of water on Ceres in the past and in the present," Carrozzo told Space.com by email. 

Furthermore, they "are among the most interesting minerals researchers can observe on the planetary surface," he said. "They are key minerals for understanding the Ceres environment because they are indicators of neutral to alkaline water."

Carrozzo's team mapped the entire surface of Ceres using Dawn's Visible and Infrared Spectrometer, searching for carbonates. Their results revealed that some of the regions required different forms of the sodium carbonates than Dawn had identified previously. The new traces of sodium carbonates are more likely to carry water inside their structure than those found before, as their signals are a close match to minerals such as trona and thermonatrite.

"Trona is a sodium carbonate with two water molecules in its structure," Carrozzo said. "When we observe it on a planetary surface, we are sure that water played a role in its formation."

Dawn's results revealed that most of the sites rich in sodium carbonate are found in the younger terrains along domes and mounds, as well as in the material thrown off by the impact that formed craters. While it is possible that the carbonates form in the heat of the impact, the researchers favor the idea that brines beneath the surface welled up to ooze through the crust. Such cryovolcanism requires that Ceres' internal temperature stay warm enough to keep water from freezing completely, remaining instead as cryomagma that's rich in sodium carbonates, Carrozzo said.

In addition to hinting at current activity on Ceres, the team's results suggest that the dwarf planet may have formed farther out in the solar system than the asteroid belt, and previous discoveries of ammonia-rich clays on the dwarf planet support that idea, Carrozzo said.

"Sodium carbonate is one of the compounds found in the plumes of Enceladus, a moon of Saturn," he added. "This finding reinforces the idea that Ceres formed in the outer solar system."

Percolating water

While Carrozzo's research focused on mapping the entire surface of Ceres, Raponi's study targeted a specific crater. (Because they are members of the Dawn team, many of the researchers, including Carrozzo and Raponi, were authors on both papers.)

Though water ice has been found in shadowy craters, most of these craters lie near Ceres' north pole. Juling Crater, however, is located in the dwarf planet's midlatitudes, where the sun is higher overhead and shadows are harder to maintain. The northern wall of the 1.6-mile-deep (2.5 kilometers) crater is almost always cloaked in shadows. It is illuminated only by light reflected from the crater floor, Raponi said.

Juling Crater has a patch of ice on its northern wall. Using Dawn's Visible and Infrared Mapping Spectrometer, Raponi and colleagues were able to watch the ice grow from 3.6 square km to 5.5 square km (1.4 square miles to 2.1 square miles) over six months. 

There are two ways the visible ice chunk can grow, the researchers said. The first possibility is that the ice could already exist beneath the shallow exterior — previous studies have shown that water ice covers much of the dwarf planet's subsurface — and then landslides along the side of the crater could slowly reveal the material, Raponi said. In that case, the itself ice wouldn't be getting larger; rather, it would be uncovered slowly.

However, the team's preferred solution involves water vapor. Geological formation similar to Earth's rock glaciers cross the floor of the crater, with a large one at the base of the northern wall. The rock walls may be the source of the ice, as the crater wall traps water molecules coming from just beneath crater floor.

"We suggested liquid water percolating under the surface and then freezing to the surface of the cold wall when exposed," Raponi said. 

The process would require a source of heat that is currently unknown, but he said other indications of water-rich minerals, such as those characterized by Carrozzo and his colleagues, suggest similar processes are occurring across Ceres.

"The increasing solar input, because of the changing season and decreasing distance of Ceres from the sun, could be the driving force of the sublimation of water from the subsurface of the floor that then, in part, condenses on the surface of the shadowed wall," Raponi said.

He pointed out that Carrozzo's research suggested a source of water-rich material rising from beneath the surface as the source of hydrated carbonates. A similar process could replenish the rock glacier on the crater floor, providing a source of water that helps to grow the icy region.

The new research reveals that Ceres isn't an inert ball of rock but rather a constantly evolving icy world.

"In general, the two works show that water is currently available on the surface of Ceres, and produces geological and mineralogical changes on its surface," he said.

Both papers were published yesterday (March 14) in the journal Science Advances, and can be seen here and here.

Editor's Note: A conversion of kilometers to miles was corrected; Raponi and colleagues saw the ice grow from 3.6 square km to 5.5 square km (1.4 square miles to 2.1 square miles).

Follow Nola Taylor Redd at @NolaTRedd, ;Facebook, or Google+. Follow us at @Spacedotcom, Facebook or Google+. Originally published on Space.com.

Haumea is a dwarf planet that orbits the sun far beyond Neptune. It is about the same size as Pluto and has two moons. One of its notable characteristics is how fast it spins on its axis. 

Discovery

Just after Christmas of 2004, a team from the Palomar Observatory, led by Mike Brown, discovered a tiny, Pluto-size body in images taken the previous spring. The astronomers nicknamed the rock "Santa."

About the same time that Brown's team published their information online, a group of astronomers from the Sierra Nevada Observatory, led by José Luis Ortiz Moreno, announced their discovery of the body in images taken in March of 2003.

Originally designated as 2003 EL61, the object was classified as a Kuiper Belt Object (KBO) until the International Astronomical Union reclassified it as the fifth dwarf planet in the solar system, following Ceres, Pluto, Eris and Makemake. (Updated estimates in 2017 put the "dwarf planet" status in doubt, however.)

The object was renamed after the Hawaiian goddess of childbirth and fertility. Its two moons were named for daughters of the goddess, Hi'iaka and Namaka, who were said to have been born from the body of Haumea.

Haumea's characteristics

Haumea takes 285 Earth-years to orbit the sun. At its closest, it only comes within 34 times the Earth-sun distance, while at its farthest, it lies more than 51 times as far away. These distances, combined with Haumea's tiny size, would generally make it difficult for scientists to accurately determine its mass and density. However, in 2005, the first of two moons was found orbiting the body, enabling scientists to determine the mass of the bodies.

Haumea spins on its axis once every four hours, the fastest spin of any known large object in the solar system.

Haumea's rapid spin keeps it from attaining a spheroid shape, instead causing it to look more like a slightly flattened football spinning end over end, as though it had been kicked. Haumea is 1,430 miles (2,300 kilometers) across at its longest axis, but less than half as wide — 619 miles (996 km) — at its shortest. Updated estimates of its mass and shape in 2017 showed that Haumea's density is likely similar to Pluto and that its shape may be too elongated to let it qualify as a dwarf planet after all.

The rapid spin allowed scientists to calculate its density, because different materials would stretch out differently. As a result, scientists think that Haumea is made up almost entirely of rock.

Observations of Haumea, however, reveal a brightly gleaming surface. Scientists have concluded that, though most of Haumea's interior is rocky, it is covered by a thin icy shell.

Haumea also appears to have a dark red spot on its surface that may contain more minerals and organic compounds than the ice around it. In 2017, astronomers also discovered a ring systemaround Haumea, which was discovered when it passed in front of the star URAT1 533-182543 on Jan. 21, 2017. The starlight also helped astronomers more accurately measure Haumea's longest axis, finding it to be roughly 17 percent larger than previous estimates.

The moons of Haumea

The two moons of Haumea were discovered after observations at the W.M. Keck Observatory in Hawaii in 2005. They are far smaller than Haumea. The largest, Hi'iaka, is only about 1 percent as massive as Haumea, while the smaller, fainter Namaka weighs only about a tenth as much. 

Hi'iaka takes 49 days to travel around Haumea in a nearly circular orbit. The inner satellite, Namaka, takes 18 days to travel around its parent body in an elliptical orbit. Both moons are thought to be composed of almost pure water-ice, which may have originally come from Haumea itself.

Although roughly a tenth of all known Kuiper Belt objects have a satellite, very few of them have multiples, making Haumea somewhat unusual.

A violent formation

Astronomers think that, in the early solar system, Haumea was much like Pluto, composed half of rock and half of water. Billions of years ago, a large object may have collided with the body, knocking most of the surface ice away and imparting a rapid spin to Haumea. The spin, in turn, elongated Haumea into its unusual shape.

The moons of Haumea may have once been part of its surface, forming much like Earth's moon did after a collision.

The discovery of small, icy debris in orbits similar to Haumea's seemed to further substantiate the idea of an ancient collision.

A rapidly changing field

Haumea's status as an object in the Kuiper Belt puts it at the frontiers of science. Small objects such as Haumea have only been studied extensively since the early 2000s, as search techniques improved to look for dwarf planets and Kuiper Belt Objects. Science also took a leap forward in 2015, when the New Horizons probe flew by Pluto and got a close-up look of the dwarf planet. 

That flyby showed that many of our assumptions about dwarf planets need some examining. For example, Pluto's terrain showed mountains and extensive evidence of liquid flow in its ancient past, meaning that Pluto had active geology — a surprise to astronomers. New Horizons will fly by the KBO 2014 MU69 on Jan. 1, 2019, providing more information about these distant objects.

Meanwhile, astronomers continue studying other dwarf planets and KBOs for more information about their formation histories. A NASA web page about dwarf planets has several general insights about these bodies, based on years of research. For example, most dwarf planets are smaller than our moon and, except for Haumea, no dwarf planet is known to have rings. 

Days on dwarf planets vary, as do the number of moons. For example, Ceres, the largest dwarf planet, has none. A moon was discovered around Makemake in 2016. "Snow White" — the temporary name for the large dwarf planet 2007 OR10 — also has a moon, astronomers announced in 2016. 

NEW ORLEANS — NASA's Dawn mission to the main asteroid belt, granted a second extended mission earlier this year, will end later next year after a final set of close-up observations of the dwarf planet Ceres.

NASA approved a second extended mission for Dawn Oct. 1, electing to keep the spacecraft in orbit around Ceres versus proposals to send the spacecraft out of orbit to flyby another asteroid. Dawn, in this new extended mission, will shift into an elliptical orbit in 2018 to provide much closer views of the surface than possible earlier in the mission.

"We're going to be using an elliptical orbit to dive closer to the surface than we have before, down to 30 kilometers altitude," said Carol Raymond, deputy principal investigator for Dawn during an Dec. 12 briefing about the mission at the Fall Meeting of the American Geophysical Union here. That altitude is significantly lower than what NASA stated when the agency announced the new extended mission. [Related: Bright Spots on Ceres, Spotted by Dawn Probe, Hint at Ancient Ocean]

Those close approaches will provide higher resolution and more accurate measurements of the chemistry of Ceres' surface, as well as "unprecedented" high-resolution images of selected features. "We're aiming to test our ideas about the origin and evolution of Ceres," she said.

That orbit, while stable, will limit the lifetime of the spacecraft. With the failure of three of its four reaction wheels, the spacecraft must use thrusters to maintain attitude control, consuming its limited supplies of hydrazine. That usage increases the closer Dawn is to Ceres.

One the spacecraft uses up that hydrazine, its mission will end since it will no longer be able to maintain attitude control. Exactly how long that will take is not yet known, she said, because of uncertainties in just how much usable hydrazine remains on the spacecraft and how to use it.

"We're still working through finalizing the plan," she said. Right now, she said the current approach called for moving into the low elliptical orbit in the spring of 2018. "We would be able to operate there on the order of three or four months."

Raymond and others involved in the mission hope that the data collected in final extended mission will help them better understand a phenomenon known as "cryovolcanism," with ice from beneath the planet's surface erupting, leaving behind bright patches of sodium carbonate. [Awesome Ceres Photos by NASA's Dawn Spacecraft]

At the briefing, scientists said that they had detected more than 300 bright spots, associated with cryovolcanism relatively recently in the dwarf planet's history. That surprised scientists, who originally thought that Ceres and other large bodies in the asteroid belt, like the asteroid Vesta that Dawn visited earlier in its mission, were relatively unchanged since early in the solar system's history.

"Before Dawn launched, we viewed Vesta and Ceres as time capsules or fossils, frozen in time from the beginning of the solar system," Raymond said. "What we did not expect was to see these abundant bright deposits splayed across the surface."

"Ceres isn't a dead body," said Caltech scientist Nathan Stein at the briefing. "The surface is still dynamic."

This story was provided by SpaceNews, dedicated to covering all aspects of the space industry.