Astronomers have spotted a remarkable gamma-ray burst (GRB) that's a real Incredible Hulk compared to other cosmic explosions of the same type.

What makes this GRB so special is the fact that the central engine powering it remained active for around 27 days, flaring in X-rays following the initial blast. That's 20 days longer than the longest previous GRB on record.

This record-breaking burst — which is designated GRB 220706A and was spotted on July 6, 2022 — is even more exciting because scientists don't know what the central engine powering it actually is.

"In a nutshell, GRB 220706A is an extremely late X-ray flare. X-ray flaring is common following GRBs, but previously it has always come within the first few days after we detect the burst," study team member Benjamin Gompertz, of the University of Birmingham in England, told Space.com.

"The fact that we see flaring at around 27 days in the GRB’s rest frame tells us that there’s an ongoing active process, and that’s unprecedented in the known population," Gompertz added. "The previous record for delayed flaring was about six days after the GRB."

What created the Incredible Hulk of gamma-ray bursts?

GRBs are some of the most powerful explosions in the cosmos. They have been linked to the collapse of a massive star, which also triggers a supernova and creates a black hole. This results in a long-duration GRB, while short-duration GRBs are thought to be triggered when two stellar remnants called neutron stars collide.

GRB 220706A is an example of an ultra-long GRB, a rare cosmic blast of gamma rays in which the engine powering the GRB stays active for longer. They are incredibly rare, with their cause still unknown.

"We don’t know what the central engine driving this outburst is, and that’s what makes this such a compelling event," Gompertz said. "The fact that we see a supernova tells us that a star has collapsed, which is the standard power source for GRBs, but it doesn’t immediately account for the extremely late flaring or unusually bright supernova. We can interpret that through previous events to some degree."

Gompertz added that another ultra-long GRB detected in 2011, GRB 111209A, was associated with an unusually bright supernova (SN2011k) that had clear evidence for a central engine. The team behind that research determined that GRB 111209A is powered by a magnetar, a neutron star with a particular powerful magnetic field. In this case, the magnetic field is rotating at around 1,000 times per second.

"Our supernova looks a lot like that one, so a magnetar might be present here. That ties in nicely with super-luminous supernovas, which are also thought to be magnetar-driven," Gompertz said. "Another possibility could be that the GRB jet and the supernova are colliding with shells of dense material that were ejected towards the end of the parent star’s life, as it became unstable and began ejecting its outer layers. This sort of event is also seen in the super-luminous supernova population."

The team isn't quite sure how the central engine of this ultra-long GRB differs from that of others and why that resulted in 27 days of flaring.

"One possibility is that it’s a much bigger star than we usually see producing GRBs," Gompertz said. "A bigger star would take longer to fall in on itself and so provide a longer-lived source of energy to power the jet."

GRB sources may be members of a stellar population of massive, compact stars called Wolf-Rayet stars. These are 10 times wider that the sun, with around 10 times the mass of our star. However, even the collapse of such a star can't explain GRB 220706A.

"To power GRB 220706A, we estimated we need a star more like 1,000 times the radius of the sun, which would require a population of stars known as blue supergiants," Gompertz said. "On the other hand, it may be the remnant that’s different. If this star produced a magnetar, it may be that 'normal' GRBs just collapse to black holes."

The team thinks that the big question with GRBs like this one is whether they are members of the normal GRB population or a different kind of event. Having this second event, in addition to GRB 111209A, with an unusually bright supernova potentially adds weight to the idea that these are different stars. But the problem is not yet solved.

"The incredibly late flares also strain our models for how jets are powered," Gompertz said. "It will be fascinating to see how future theoretical work can incorporate a power source from a collapsing star that can last for a month!"

There could be even longer-lasting GRBs out in the cosmos that we have thus far failed to detect. Gompertz explained why such detections are tricky.

"GRBs this long are hard to detect because most of the satellites we use to find them are in low Earth orbit, which means the target is periodically blocked every 90 minutes or so," he explained. "That's fine for your typical 10- to 100-second-long GRB but becomes a nuisance when tracking much longer events. Long-lasting GRBs also seem to be more active in the X-rays rather than the gamma rays."

The University of Birmingham researcher added that newly launched missions like the Einstein Probe, which is more sensitive in X-rays than gamma rays, may be the perfect instruments to find more ultra-long GRBs.

"With any luck, we’ll get a few more of these to chase so that we can start trying to understand the incredible power sources that drive them," Gompertz concluded.

A pre-peer-reviewed version of the team's research is featured on the repository site arXiv.

Now you see them, now you don't. Scientists have discovered that some of the universe's most powerful explosions, hypernovas, may not happen at all.

These explosions, known as hypernovas, were first proposed to explain unusual stars in the halo of our galaxy, the Milky Way, and in a neighboring dwarf galaxy. It was suggested that these stars could only form from the debris of an explosion 10 times more powerful than the 'average' supernovas.

The team behind these new findings suggests that ordinary supernovas could actually account for these stars when the uneven or non-spherical way they fling out matter is considered.

"If we look at a supernova today, the star's materials are not spread evenly. Oxygen might predominantly fly in one direction, sulphur in another. New stars might form from a mix of pieces of the supernova, not its overall mix of elements," team leader Anmol Aggarwal of University College London (UCL) said in a statement. "We developed mathematical models that took account of this and found in all cases that stars with a very unusual mix of ingredients were most likely formed from ordinary supernovas.

"All the evidence we see for hypernovae is suddenly gone."

Hypernova vs. supernova: What's the difference?

Supernovas occur when massive stars run out of fuel for nuclear fusion, effectively ending their lives. This results in the star's core collapsing, sending shockwaves rippling through its outer layers, causing explosions we call supernovas.

Hypernovas are proposed to occur in a similar way, but for an even more massive and rapidly spinning star. This results in a vastly more energetic explosion.

When supernovas or hypernovas happen, they fling elements that the dying star has forged throughout its lifetime into their surrounding cosmic environments. These elements eventually become the building blocks of the next generation of stars.

That means analyzing the chemical signatures of stars can tell stellar scientists about their family histories.

"Just before a star goes supernova, it has layers like an onion, with heavier elements at the center and lighter ones further out. Our model looks at how much material from each layer or each region would be needed to fit the observed star," Ralph Schoenrich of Mullard Space Science Laboratory at UCL said. "We still don’t know how well the supernova material gets mixed before it forms new stars. That is despite decades of work in this area. Our research suggests some mixing goes on, but incomplete mixing.

"We need to take this into account in our models of how chemicals evolve in galaxies and of how the interstellar medium works."

The team began their investigation by observing four stars that are suspected to have been forged from material ejected in a hypernova explosion. Three of those stars were more likely to have been created after supernovas, the team concluded.

The scientists then studied a single red giant star in the halo of the Milky Way with an odd chemical composition, including an overabundance of heavy elements like silver and uranium. These are too heavy to be forged in the cores of all but the most massive stars, the kind of stars that go hypernova.

Such elements could also be created when two massive and dense stellar remnants called neutron stars collide and merge. However, this star doesn't have certain other heavy elements that would be present after a neutron star collision.

This team considered the origins of this star using a model of the Milky Way that has been rapidly enriched with elements heavier than hydrogen and helium, which astronomers call metals, via the death of the first generation of stars.

The rapid speed at which the star spins and the fact it exists at the outskirts of the Milky Way led the team to conclude that this star escaped a metal-poor dwarf galaxy and was eventually dragged into our galaxy. The event that created it, they concluded, was the combination of a neutron star merger and an ordinary supernova.

No hypernova required. An asymmetrical supernova would be enough, the scientists found.

The team's research was published as two papers in the journal Monthly Notices of the Royal Astronomical Society.

Using the Chandra X-ray spacecraft, astronomers have seen a supermassive black hole jet churning and "cooking" gas surrounding a galaxy nicknamed the "red potato." And this potato is seen as it was when the universe was around 2 billion years old.

The galaxy in question is officially designated MQN01 J004131.9-493704 and is located about 11.7 billion light-years from Earth at the intersection of a vast cosmic web along which galaxies formed in the early universe. Originally discovered by the James Webb Space Telescope (JWST), the odd, blob-like appearance of the galaxy is why it has such a peculiar nickname.

The red potato sits in a cosmic "pot" of cold and dense gas. This is a little puzzling, as this should mean that stars are actively forming around it, but that isn't happening. New research offers an explanation: a supermassive black hole in the vicinity of the red potato is churning and heating the galaxy's pot of gas. This could be preventing the gas from cooling and collapsing to birth stellar bodies.

“Stars are not forming like we thought they would, so we went searching for the reason why," team leader Weichen Wang of the University of Milan-Bicocca in Italy said in a statement. "We found there may be a cook in this cosmic kitchen."

An unexpected chef

A supermassive black hole's interference with the red potato was first indicated by the fact that its surrounding gas is unexpectedly turbulent in comparison to similar gas clouds around similar galaxies.

Wang and colleagues set about hunting for the source of this turbulence with Chandra. That's when they found a black hole jet pointed toward the red potato, which they reasoned must be slamming into this ancient galaxy's gas envelope.

"If the black hole's jet is stirring up the gas around the red potato, it could greatly slow down how quickly the galaxy can acquire new, fresh material to form stars," team member Sebastiano Cantalupo of the University of Milan-Bicocca said in the statement. "With the energy from the stirring, the galaxy will starve and not be able to produce new stars at the rate expected for similar galaxies at the same cosmic epoch."

The meddling supermassive black hole is located in a galaxy around 200,000 light-years from the red potato, and this galaxy is actually very actively forming new stars. Indeed, other galaxies in the vicinity of the Red Potato are also birthing new stars.

This discovery, as part of some of the first research to investigate the behavior of gas around non-star-forming galaxies, could be vital in improving our understanding of how neighboring galaxies interact and, occasionally, interfere with each other's evolution.

"The red potato is leaving crumbs of information that may help us track down the answers to some really big questions," team member Andrea Travascio, also of the University of Milan-Bicocca, said. "Quite an important job for a galactic spud like this."

The team's research was published on July 7 in the journal Astronomy & Astrophysics.

Using NASA's long-serving Hubble Space Telescope, astronomers have discovered that a stellar explosion in the Milky Way is blasting out cosmic bullets travelling at 20 million miles per hour.

The cosmic explosion in question is V445 Puppis, which erupted in 2000 and is the only known "helium nova" in our galaxy. Though astronomers have been studying V445 Puppis for two decades, much of the phenomena associated with it were shrouded in mystery due to a vast cloud of dusty debris that surrounded this nova.

When this debris finally cleared, a team of researchers was able to peer into V445 Puppis using Hubble, NASA's exoplanet-hunting spacecraft TESS (Transiting Exoplanet Survey Satellite), and the Earth-based Very Large Telescope (VLT), along with an array of other instruments. This allowed them to discover not only the "bullets", clumps of potentially oxygen-rich gas it is firing, but also the true nature of this system. This revealed that V445 Puppis consists of a dead star hungrily feeding on a companion star that is, by itself, a rare find. Thus, this system offers scientists a rare chance to study one of the rarest types of binary systems and one of the rarest cosmic explosions.

"The origin of these 'bullets' is a mystery. We suspect that these originated post-outburst, but 'bullets' of this kind have not been observed in any other nova," team member John Mills, a researcher at the University of Warwick in the UK, said in a statement.

What is a helium nova?

Helium novas like V445 Puppis occur when a white dwarf dead star cannibalistically strips helium-rich but hydrogen-poor matter from a star that has already lost its outer layer of hydrogen, exposing inner layers of helium; forming a rare "helium star." By contrast, "ordinary" novas are explosions triggered by the buildup of stolen stellar matter rich in hydrogen, not helium.

As the material accumulates on the surface of the white dwarf (a type of stellar remnant left behind when stars around the mass of the sun die) it creates runaway pressures and temperatures that eventually trigger a thermonuclear explosion.

When V445 Puppis went nova back in late 2000, it launched vast, twin plumes of debris that resemble butterfly wings. Stretching out for more than a trillion miles, astronomers initially spotted this bipolar outflow in infrared. The nova also spawned a thick disc of dust that completely obscured the binary star system. That cloud persisted for over two decades, preventing astronomers who were investigating the expanding debris from determining what kind of stars the blast originated from.

Once the debris cleared, this team determined that the system contained a helium star, one of only a few thousand of these stripped stellar bodies to be discovered among the billions of stars that populate the Milky Way.

"The culprits behind this galactic eruption have been an enduring mystery over the past 25 years, which is why it is very exciting to confirm that this helium nova was the result of a helium star accreting onto a white dwarf," Mills said.

The findings also revealed cosmic "bullets" that are even more remarkable, as they have never been seen around any other novas. Intriguingly, the team also found that V445 Puppis may be about to go nova again, and this could lead to an entirely different type of cosmic explosion.

Is V445 Puppis about to blow its top again?

Mills found that the white dwarf in V445 Puppis has overcome its stellar indigestion and is once again feeding on its companion helium star.

This is the process that led to the initial helium nova, and could mean that another episode of this rare type of cosmic explosion is soon to occur.

That has implications for our understanding of another type of cosmic eruption, this time a type of supernova called a Type Ia supernova. These occur when white dwarfs overfeed on companions and are completely destroyed by the resultant explosion.

Scientists have long suspected that repeated helium nova eruptions could lead to final Type Ia supernovas.

A new Type Ia supernova would be exciting because these events are so regular in terms of their light emission that they can be used as so-called "standard candles" to measure cosmic distances and gauge the age of the universe.

This means that they can also be employed in the quest to understand how fast the universe's expansion is proceeding, and the influence of the mysterious force called dark energy on this process.

"I look forward to seeing how this result may help us uncover what powers other similar hydrogen-poor astronomical explosions, such as the famous Type Ia supernovas," Mills said.

The team's research was presented this week at the Royal Astronomical Society's National Astronomy Meeting in Birmingham, UK.

The Zwicky Transient Facility has reached an incredible milestone: It has classified over 10,000 cosmic explosions that mark the deaths of massive stars and the feeding frenzies of vampire stellar remnants. These events, called supernovas, are undoubtedly some of the most fearsome and powerful events in the universe.

Since 2012, humanity has discovered almost 16,000 supernovas. The Zwicky Transient Facility (ZTF), which began operations in 2017 using the 48-inch telescope at Palomar Observatory, is responsible for almost two-thirds of these detections. That makes it the largest and arguably most successful supernova surveyor to date.

"There are trillions of stars in the universe, and about every second, one of them explodes," California Institute of Technology astronomer Christoffer Fremling said in a statement. "Reaching 10,000 classifications is amazing, but what we truly should celebrate is the incredible progress we have made in our ability to browse the universe for transients, or objects that change in the sky, and the science our rich data will enable."

Fremling is the leader of the Bright Transient Survey, an endeavor that uses the ZTF to discover and classify new supernovas.

It should probably come as no surprise that the ZTF has been so revolutionary in supernova science because it has pedigree even in its name. The project is named for Caltech astronomer Fritz Zwicky.

In the 1930s, Zwicky began hunting cosmic explosions with a small telescope from the frigid heights of the Palomar Mountain near San Diego. By the 1940s, Zwicky moved his hunt for supernovas to the 48-inch Samuel Oschin telescope at Palomar Observatory, along with his collaborator, Walter Baade.

Together, Zwicky and Baade discovered a multitude of these explosions, coining the term "supernova" to describe them. Finding over 120 supernovas across his career, Zwicky, who passed away in 1974, held the record for hunting these stellar explosions until 2009. Now, the supernova-hunting facility that shares Zwicky's name continues his record-setting work.

Why supernova classification matters

The ZTF doesn't just hunt supernovas. This project is capable of detecting a range of transient astronomical events, which are events that occur and then fade from the sky.

Transient events tracked by the ZTF include rapidly moving asteroids in the solar system, black holes ripping apart stars and devouring them in so-called tidal disruption events (TDEs), and colliding stars that eventually merge.

The ZTF detects hundreds of thousands of these transient events each night. Once verified, these detections are sent to an astronomy database called the "Transient Name Server." From there, they are available to the astronomical community as a whole. This allows astronomers to follow up on the detection of supernovas using a range of telescopes around the globe.

ZTF principal investigator and Caltech astronomer Mansi Kasliwal says that the "name of the game" for ZTF studying supernovas is to obtain spectra.

"Discovery is only the first step," she said. "Spectra are the most valuable currency in this field. You don't know the physics and chemistry of the object without that."

Obtaining the spectrum of light from these supernovas allows scientists to determine a range of characteristics. That includes their distances from Earth, the chemical compositions of the stars from which they erupted, and, crucially, what type of supernova the ZTF has witnessed.

The supernovas that relate to the deaths of massive stars are referred to as core-collapse supernovas. They occur when massive stars run out of fuel for nuclear fusion, and the outward flow of energy that supports them against the inward push of gravity ceases.

The core of the massive star collapses to create a neutron star or a black hole. This collapse sends shockwaves rippling into the outer layers of the star, causing a core-collapse supernova.

Another type of supernova occurs when the remnant of an already dead star, a white dwarf, vampirically strips material away from a companion star. This material builds up on the surface of the white dwarf, triggering a thermonuclear explosion, which is seen as a Type Ia supernova.

This process usually obliterates the white dwarf, but there are rare events called Type-Iax supernovas in which the stellar remnant lives on as a ravaged "zombie star."

It is vitally important to identify Type Ia supernovas because they are a crucial astronomical tool. Because the light output of Type Ia explosions are so uniform, they are known as "standard candles," and they can be used as milestones on a giant cosmic measuring stick.

The ZTF doesn't just hunt supernovas for other facilities to identify, however. Using two spectrographs at Palomar Observatory, the ZTF project can also classify its own supernovas and supernovas detected by other facilities.

"Back when we started this project, we didn't know how many astronomers would follow up on our detections," Fremling said. "To see that so many have is a testament to why we built ZTF: to survey the whole sky for changing objects and share those data as rapidly as possible with astronomers around the world."

One of the project's biggest achievements was the discovery of Supernova Zwicky (SN Zwicky), a cosmic explosion warped by an effect called "gravitational lensing," which allowed it to appear four times in the same image.

"I was observing that night and was absolutely stunned when I saw the lensed image of SN Zwicky," Fremling explained in a Caltech news story last year. "We catch and classify thousands of transients with the Bright Transient Survey, and that gives us a unique ability to find very rare phenomena such as SN Zwicky."

Moving forward from this milestone, data from the ZTF will continue to help astronomers answer questions about stellar life and death — and may even assist in solving the mystery of dark energy, the unknown force driving the acceleration of the expansion of the universe.

Zwicky's legacy of supernova science is in good hands.

Last week, a group of astronomers announced that they had for the first time discovered the source galaxy for a mysterious type of event known as a fast radio burst (FRB). But only a few days later, another group of scientists produced informal research that suggested otherwise.

FRBs release the same amount of energy in a single millisecond as the sun produces over 10,000 years. But what causes them and even where they come from has remained a mystery.

Evan Keane, a project scientist at the Square Kilometer Array Organization, and colleagues authored the original paper that claims to narrow down the source location of an FRB by tracing what they interpreted as the afterglow of whatever caused the FRB. But another group, led by Peter Williams, a postdoctoral astronomer at the Harvard-Smithsonian Center for Astrophysics, claims it could just be the belches of a monster black hole. [Top 10 Strangest Things in Space]

"We astronomers can currently only get relatively poor localizations for FRBs. For the search performed by the Keane team, they can narrow it down to an area about a quarter the size of the full moon," Williams told Space.com by email.

When Keane's team reviewed the region from which the FRBs originated, they found a faint glow within a galaxy along the line of sight. After watching it slowly fade over the course of six days, they concluded that the light had been produced by a sort of cataclysmic collision between powerful objects, such as a pair of merging black holes, which could have subsequently produced the original FRB.

But Williams and his team suggest that the glow is instead the result of the bright activity associated with a supermassive black hole at the heart of a galaxy, a feature known as an active galactic nuclei (AGN).

"The Keane team's paper does not consider the possibility that the origin galaxy is an AGN," Williams said. "Frankly, I'm not sure why this possibility was not investigated in the paper."

Questionable origins

Every day, an estimated 10,000 FRBs explode across the sky. Despite their abundance, only a handful have been detected since their discovery in 2007. Most of these have been found using the Parkes radio telescope in Australia.

Pinpointing the sources of FRBs has remained a challenge over the decade and a half since they were first spotted. A number of causes have been suggested for FRBs. These include collisions between powerful objects such as dense neutron stars, which would demolish the sources. Other researchers have suggested less violent origins, such as changes in the magnetic field of highly magnetized neutron stars (the remains of collapsed stars) known as magnetars, which would allow the source to survive the FRB process.

Keane's team followed the trail of the FRB back to a galaxy with a dim afterglow suggestive of a powerful collision. According to Williams, however, following the trail is inconclusive.

"You can fit a lot of galaxies in that search area, so your odds of seeing an unrelated radio variable are not so bad," Williams said.

According to Williams' co-author Edo Berger, a professor of astronomy at Harvard University, the location uncertainty region for the FRB is about 200 times larger than the size of the signal. The FRB could come from anywhere within that region. The radio waves could have even passed through the galaxy, and their source could be hidden on the other side, forever out of sight.

"One reason that FRBs are exciting is that radio pulses can travel through all sorts of stuff," Williams said. "They would have no problem passing through a galaxy."

Red flags

Most galaxies contain a supermassive black hole at their heart. In the Milky Way and others, the black hole is relatively quiet, sporadically consuming stars and dust. In others, material is constantly flowing into the black hole, and the resulting radiation produces a bright glow that can be seen across the universe. The strength of the signal can vary as the supply of material changes over time.

For Williams and his colleagues, the constant glow from the proposed source galaxy raised a red flag.

"I think that Keane et al glossed over the steady radio emission after the first six days," Berger said. "It was bright enough that only an AGN origin makes sense. This was what alerted us to a problem with their paper as soon as we read it."

Williams' team used the Very Large Array, run by the National Radio Astronomy Observatory, to observe the galaxy and found that the glow had not only remained steady but had brightened since the original observations, a finding Berger said supported the idea of an AGN source.

No current models suggest that an AGN could produce the fast radio bursts. Berger deemed them unlikely sources, because events that occur on such short timescales are difficult to produce near black holes. Williams also thinks it unlikely but not necessarily unreasonable.

"We know little enough about the physics of FRBs that I wouldn't want to say it's impossible," Williams said. "In fact, I wouldn't be shocked if an enterprising theorist gets inspired to cook up just such a model based on the past week's events."

Williams' team posted an informal paper online, which alerted other scientists of their conclusions.

"It looks like it comes from an AGN because of its spectrum and persistence," astronomer Avi Loeb, referring to the afterglow, told Space.com. Loeb serves as chairman of the Astronomy department and Direct of the Institute for Theory & Computation at Harvard University, and was not involved in either study.

Keane's team used the proposed source to "weigh" the material in the space it passed through. Their calculations matched models of the distribution of normal and dark matter through space. But according to Berger, those results could be a coincidence. The FRB could lie at approximately the same distance as the proposed source galaxy, which would give similar numbers even if it isn't in the same direction.

Loeb agreed that it was likely a coincidence.

"Given the error bars on the measurement, such a coincidence would not be unusual," he said.

Space.com reached out to the authors of the original research to ask for their thoughts on the idea of an AGN as the source of the glow.

"We are, of course, aware of [Williams'] work, and indeed are performing our own ongoing studies," Keane told Space.com.

He said that once the studies were complete, they would be reported in peer-reviewed scientific literature, "which is where scientific debate happens." He declined to comment on the informally published results posted by Williams.

"We really can't rush the scientific process," Keane said. "I'd have said the same to you if, a couple months ago, you had asked me about last week's or this week's Nature papers, when they were still in the peer-review process."

Williams and his colleagues intend to continue observing the proposed source galaxy, monitoring it for activity that might further support or deny the idea that the glow spotted by Keane's team came from an AGN rather than an FRB. Still, without more detailed observations, definitively pinpointing the source may prove impossible.

"We may never find out where this FRB came from, or even be able to conclusively prove that it did not come from the proposed galaxy," Williams said. "But I think we are well on our way to showing that there is a compelling alternative hypothesis that explains the galaxy observations without requiring that the FRB originated from the galaxy."

[Editor's Note: This article previously stated that Williams' team used NASA's WISE telescope for follow-up obervations, which was incorrect. The group made their observations using the Very Large Array, which is managed by the National Radio Astronomy Observatory.]

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