Scientists may have "seen" dark matter for the first time, thanks to NASA's Fermi gamma-ray space telescope. If so, this would mark the first direct detection of the universe's most mysterious substance.

Dark matter was theorized in 1933 by astronomer Fritz Zwicky, who found that the visible galaxies of the Coma Cluster lacked the necessary gravitational influence to prevent this cluster from flying apart. Then, in the 1970s, astronomer Vera Rubin and colleagues found the outer edges of spiral galaxies were spinning at the same rate as their centers, something that would only be possible if the major amount of mass in these galaxies wasn't concentrated at their centers, but rather more widely dispersed. These aren't direct observations of dark matter, of course, but inferences made using dark matter's interactions with gravity as well as the influence gravity then has on ordinary matter and light. Still, because of these findings, s astronomers have since calculated that all large galaxies are embedded within vast haloes of dark matter that expand way beyond the limits of visible matter in galaxies (such as galactic haloes of stars).

The particles of this mysterious substance are now estimated to outweigh the particles that make up everyday matter by a ratio of five to one. That means everything we see around us on a day-to-day basis — stars, planets, moons, our bodies, next door's cat, and so on — all account for just 15% of the matter in the universe, with dark matter accounting for the other 85%. Adding to the mystery of dark matter is the fact that, because it interacts with electromagnetic radiation so weakly, or not at all, it doesn't emit, absorb, or reflect light. Thus, it is effectively invisible in all wavelengths of light — or at least, we thought it was.

There is one possibility that would result in dark matter producing light. If dark matter particles "annihilate" when they meet each other and interact, much as matter and its counterpart antimatter do, then it should produce a shower of particles, including photons of gamma-rays that, while invisible to our eyes, could be "seen" by sensitive gamma-ray space telescopes. One of the suggested "self-annihilating" particles theorized to comprise dark matter are so-called "Weakly Interacting Massive Particles" or "WIMPS."

A team of researchers, led by Tomonori Totani from the Department of Astronomy at the University of Tokyo, trained the Fermi spacecraft on the regions of the Milky Way where dark matter should congregate, namely at the center of our galaxy, and hunted for this telltale gamma-ray signature.

Well, Totani thinks we finally found that signature.

"We detected gamma rays with a photon energy of 20 gigaelectronvolts (or 20 billion electronvolts, an extremely large amount of energy) extending in a halolike structure toward the center of the Milky Way galaxy," Totani said. "The gamma-ray emission component closely matches the shape expected from the dark matter halo."

And this isn't the only close match. The energy signature of these gamma-rays closely matches those predicted to emerge from the annihilation of colliding WIMPs, which are predicted to have a mass around 500 times that of a proton, the ordinary matter particles found at the heart of atoms. Totani suggests there aren't any other astronomical phenomena that easily explain the gamma-rays observed by Fermi.

"If this is correct, to the extent of my knowledge, it would mark the first time humanity has ‘seen’ dark matter. And it turns out that dark matter is a new particle not included in the current standard model of particle physics," Totani said. "This signifies a major development in astronomy and physics."

While Totani is confident that what he and his colleagues have detected is the signature of dark matter WIMPs annihilating each other at the heart of the Milky Way, the scientific community in general will require more hard evidence before the book is closed on this nearly century-old mystery.

"This may be achieved once more data is accumulated, and if so, it would provide even stronger evidence that the gamma rays originate from dark matter," Totani added.

The team's research was published on Tuesday (Nov. 25) in the Journal of Cosmology and Astroparticle Physics.

From galaxy rotation curves that defy Newton's laws to gravitational lensing that bends light in eerie ways, scientists have been piecing together clues about dark matter like interstellar sleuths.

Particle physicists, astronomers, and cosmologists have built massive underground detectors, launched satellites, and even proposed entire new particles — all in pursuit of this elusive substance.

This quiz will test your knowledge of the strange, shadowy realm of dark matter. We'll explore the history of its discovery, the theories that try to explain it, and the cutting-edge experiments designed to catch it in the act.

Whether you're a seasoned space nerd or just curious about the universe's biggest mystery, you're in for a brain-bending ride.

Try it out below and see how well you score!

Dark matter, one of the universe's best kept secrets, may have been quietly painting the cosmos in faint, detectable hues of red and blue all along, a new study suggests.

Dark matter makes up more than 80% of the matter in the universe, yet it doesn't emit, absorb, or reflect light, making it impossible to observe directly. Now, a new theoretical study by scientists at the University of York in the U.K. suggests light passing through dark-matter-rich regions of space could pick up a faint tint — slightly red or blue, depending on the kind of dark matter it encounters.

The effect would be extraordinarily subtle, far too weak for current telescopes to detect, but potentially measurable with the next generation of ultra-sensitive observatories, the researchers say.

"It's a fairly unusual question to ask in the scientific world, because most researchers would agree that dark matter is dark," study co-author Mikhail Bashkanov of the University of York said in a statement. "But we have shown that even dark matter that is the darkest kind imaginable — it could still have a kind of colour signature."

The team likens the concept to the "six handshakes rule," the 20th-century theory that any two people on Earth are connected by a chain of, at most, six acquaintances. In a similar way, the study suggests, even if dark matter doesn't interact directly with light, it might do so indirectly through intermediate particles that both sides "know," including the Higgs boson, the so-called "God particle" that represents the Higgs field, which is responsible for giving other particles their mass.

This indirect link could allow photons, the particles of light, to scatter ever so slightly off dark-matter particles, leaving behind a whisper of color or polarization "fingerprint" in the light, the study suggests.

"It's a fascinating idea, and what is even more exciting is that, under certain conditions, this 'colour' might actually be detectable," Bashkanov said in the statement. "With the right kind of next-generation telescopes, we could measure it."

In their study, published earlier this month in the journal Physics Letters B, Bashkanov and his team carried out what they say are the first detailed calculations of how strongly light could scatter off dark matter.

The findings suggest that if dark matter is made up of Weakly Interacting Massive Particles, or WIMPs, which interact through the weak nuclear force, then light passing through a WIMP-rich region would lose some of its high-energy blue photons first, leaving the transmitted light slightly red-tinted. In contrast, if dark matter interacts only through gravity, photons would scatter in the opposite way, giving the light a faint blue shift, the study notes.

In both situations, the interactions are minute but not zero, researchers say, meaning dark matter could leave behind a detectable "fingerprint" on light that travels through dense regions of it, such as the centers of galaxies or galaxy clusters.

Their calculations show that these effects could slightly distort the light spectrum of distant objects. A galaxy's glow, for instance, might appear microscopically redder or bluer depending on the dominant type of dark matter lying between it and Earth. In principle, such differences could help scientists distinguish between dark-matter models based on whether cosmic light skews red or blue as it travels through dark-matter-rich space.

"Right now, scientists are spending billions building different experiments — some to find WIMPs, others to look for axions or dark photons," Bashkanov said in the same statement. "Our results show we can narrow down where and how we should look in the sky, potentially saving time and helping to focus those efforts."

Detecting such tiny shifts would require ultra-precise telescopes and painstaking analysis of light that has traveled billions of light-years across the cosmos. Future observatories with exceptional spectral and polarization sensitivity, such as the European Extremely Large Telescope and NASA's Nancy Grace Roman Space Telescope, could one day test these predictions.

If confirmed, the findings would open an entirely new observational window on dark matter, bringing scientists a step closer to unraveling one of the greatest mysteries in cosmology.

Scientists are about to unleash a powerful new weapon in the hunt for dark matter, the mysterious substance that accounts for around 85% of the "stuff" in the universe. Like a super-weapon developed by a stereotypical supervillain, this new dark matter detector is hidden over a mile deep beneath the French Alps.

This highly sensitive detector, developed by an international team of researchers including scientists from Johns Hopkins University, will expand the search for potential dark matter particles beyond its current parameters. It could thus provide evidence for the existence of a particular dark matter candidate particle, or the detector could help rule out some suspects.

This evidence for or against certain candidates for dark matter could potentially find new particles less massive than many current dark matter candidates. Or, as team member and Johns Hopkins researcher Danielle Norcini puts it, "WIMPier than the WIMPS (Weakly Interacting Massive Particles)."

"Dark matter is one of the most important ingredients that shape our universe and also one of the greatest cosmological mysteries," Norcini said in a statement. "Our prevailing theories about the nature of dark matter aren't yielding results, even after decades of investigation.

"We need to broaden our search, and now we can."

New dark matter detector goes underground

Dark matter is such a mystery for scientists because, despite outweighing everyday particles in the universe by a ratio of 5 to 1, we have no idea what dark matter is. We do know what it (probably) isn't, however.

Dark matter is effectively invisible because it doesn't directly interact with electromagnetic radiation, or light, or it does, and this interaction is so weak we can't see it. Dark matter does interact gravitationally, and this has allowed astronomers to discover that entire galaxies like the Milky Way are embedded in vast haloes of dark matter that extend far beyond the reaches of those galaxies' visible matter.

The particles that comprise atoms, electrons, protons, and neutrons do interact with light, however, so we know that dark matter isn't the same "stuff" that comprises stars, planets, moons, asteroids, animals and everything else we can see.

This has prompted a search for particles beyond the so-called standard model of particle physics, which was completed when scientists discovered the Higgs Boson at the Large Hadron Collider (LHC), the world's most powerful particle accelerator, back in 2012.

But, despite scientists using instruments like the LHC to smash together protons and atomic nuclei together at near the speed of light, a potential dark matter particle has thus far failed to manifest in the lab. That is also despite 4 decades of searching.

Traditional dark matter detectors are designed to spot tiny flashes of energy caused when dark matter particles, whatever they may be, collide and interact with particles of ordinary matter. Current detectors use heavy atoms like xenon and argon, which should recoil if their nucleus is struck, much like colliding billiard balls. The energy from this recoil would be recorded and assessed as a potential dark energy signal.

The problem with this is that recoiling, essential for detection, only occurs if the dark matter particle that strikes the atomic nucleus has a similar mass to the struck nucleus.

That means attempts to detect dark matter particles in this way have historically focused on particles with nucleus-sized masses, or WIMPs. However, this team reasons that if WIMPs existed, the 40 or so years of hunting that have been conducted thus far should have turned up a signal.

However, if dark matter particles are of smaller masses, this detection method won't work. Going back to the billiard ball analogy, imagine replacing the billiard balls with bowling balls and the cue ball with a ping-pong ball. Lighter dark matter particles wouldn't have the heft to cause a nucleus of xenon or argon to recoil. However, they could cause recoil when striking much less massive particles like electrons. That smaller recoil would result in a smaller flash of energy requiring a more sensitive detector to spot it

To develop a more sensitive dark matter detecting kit, this team turned to silicon skipper charged-couple devices or "CCDs." These advanced sensors employ silicon to detect much lower-energy events than other CCDs can spot.

The device is capable of detecting signals emitted by single electrons as they orbit a much larger atomic nucleus. This should allow researchers to hunt for dark matter particles similar in size to electrons.

Such sensitivity requires an extremely well-shielded environment to prevent any signal from being washed out by unwanted signals or "noise" from surrounding naturally occurring events. Hence, this team is taking their detector around 1.2 miles (2 kilometers) beneath the French Alps.

In this underground lair, vast amounts of bedrock can block out cosmic rays, charged particles streaming to Earth from space, filtering out signals caused when they strike atoms, while ancient lead and special lab-grown copper reduce background radiation and noise associated with that.

The current detector is a proof-of-concept prototype that features 8 silicon skipper CCDs. The next step is to scale this up to 208 sensors to create a full-sized experiment, which has been dubbed DAMIC-M.

The larger capture area of DAMIC-M will boost the chances of capturing an interaction between electrons and dark matter particles, making this detector the most sensitive in the world to potential "WIMPier" particles.

"Trying to lock in on dark matter's signal is like trying to hear somebody whisper in a stadium full of people. That's how small the signal is," Norcini concluded. "While we haven't discovered dark matter yet, our results show that our detector works as designed, and we are starting to map out this unexplored region."

The team's research was published on Aug. 13 in the journal Physical Review Letters.

"Dark dwarfs" may sound like a new race of Sauron-worshipping Middle-Earth dwellers, but it's actually a new type of stellar body proposed to exist at the hearts of galaxies.

The prefix "dark" here doesn't refer to the Dark Lord, but rather to dark matter, the mysterious stuff that accounts for 85% of the matter in the universe. This form of matter remains effectively invisible because it doesn't interact with light, but it does interact with gravity.

New research suggests that brown dwarfs, also known "failed stars," could act as gravitational traps for dark matter, forcing the exotic stuff to interact with itself. This releases energy, heating these failed stars, and turning them from brown dwarfs to dark dwarfs. And the more dark matter that dark dwarfs accumulate, the more energy these darkside stars would radiate.

If this idea is correct, and dark dwarfs do dwell at the heart of the Milky Way and other galaxies, where dark matter is most abundant, then it gives scientists a strong hint about what hypothetical undiscovered particles must make up this mysterious form of matter.

That's because only certain dark matter particles interact with each other and "self-annihilate," releasing energy. Arguably, the most favored example of such self-interacting particles are Weakly Interacting Massive Particles (WIMPs).

"Dark matter interacts gravitationally, so it could be captured by stars and accumulate inside them," team member Jeremy Sakstein of the University of Hawai‘i said in a statement. " If that happens, it might also interact with itself and annihilate, releasing energy that heats the star."

Brown dwarfs turn to the dark side

Brown dwarfs get the unfortunate nickname "failed stars" because, despite forming just like stars from a cloud of collapsing gas and dust, they fail to gather enough mass to trigger the fusion of hydrogen to helium in their cores.

This process powers main sequence stars like the sun. Brown dwarfs faintly glow because some nuclear fusion occurs within them and because they contract under their own gravity. But when they are located at the heart of galaxies, these failed stars may find an alternative power source.

"Dark dwarfs are very low mass objects, about 8% of the sun’s mass," Sakstein explained. "These objects collect the dark matter that helps them become a dark dwarf."

Dark matter interacts gravitationally but doesn't interact with other matter, meaning it can sink to the hearts of galaxies without too much opposition. That means the centers of galaxies are abundant with dark matter and are thus the most likely place to find dark dwarfs.

"The more dark matter you have around, the more you can capture," Sakstein said. "And, the more dark matter ends up inside the star, the more energy will be produced through its annihilation."

Dark matter can only power dark dwarfs if it interacts with itself. Even if these interactions are rare or "weak" (which would explain why we've not detected them yet), where dark matter is gravitationally crammed together, like at the heart of a brown dwarf, they could become frequent.

So the existence of dark dwarfs may eliminate non-interacting candidate particles for dark matter, as well as particles that are too light. That includes perhaps the leading dark matter candidate at the moment, axions.

"For dark dwarfs to exist, dark matter has to be made of WIMPs, or any heavy particle that interacts with itself so strongly to produce visible matter," Sakstein said.

Of course, this would all be idle speculation if the team couldn't suggest a way to detect dark dwarfs and distinguish them from non-dark matter-powered brown dwarfs or ordinary stars.

The researchers suggest a particular chemical marker that could be a dead giveaway of dark dwarfs — the isotope lithium-7, which burns easily and is therefore quickly consumed by ordinary stars.

"There were a few markers, but we suggested the lithium-7 because it would really be a unique effect," Sakstein said. "So if you were able to find an object which looked like a dark dwarf, you could look for the presence of this lithium because it wouldn’t be there if it were a brown dwarf or a similar object."

The team thinks that powerful telescopes like NASA's James Webb Space Telescope (JWST) could already be capable of detecting cool and dim dark dwarfs.

"The other thing you could do is to look at a whole population of objects and ask, in a statistical manner, if it is better described by having a sub-population of dark dwarfs or not," Sakstein said.

Should a dark dwarf be detected at the heart of the Milky Way, Sakstein argues this would be "reasonably strong" evidence of WIMPS as dark matter particles.

"With light dark matter candidates, something like an axion, I don’t think you’d be able to get something like a dark dwarf. They don’t accumulate inside stars," the researcher said. "If we manage to find a dark dwarf, it would provide compelling evidence that dark matter is heavy, and interacts strongly with itself, but only weakly with the Standard Model ["ordinary" matter]. This includes classes of WIMPs, but it would include some other, more exotic models as well.

"Observing a dark dwarf wouldn’t conclusively tell us that dark matter is a WIMP, but it would mean that it is either a WIMP or something that, for all intents and purposes, behaves like a WIMP."

The team's research was published in the Journal of Cosmology and Astroparticle Physics (JCAP).

What mysteries of the universe could the world's largest and most powerful particle accelerator unlock?

The Large Hadron Collider (LHC) at CERN (the European Organization for Nuclear Research) near Geneva, Switzerland was just switched back on for the third time after a three-year hiatus planned to implement upgrades. In the 14 years since it was first turned on, the particle accelerator has explored some of the biggest mysteries in the universe, colliding countless particles at near the speed of light in a tunnel  328 feet (100 meters) underground. 

One of the most amazing things about the LHC is that scientists don't know exactly what might happen when they smash protons together at nearly the speed of light. Despite its years of driving groundbreaking science, at the end of Run 2 in 2018, scientists estimated that the LHC had only delivered about 3% of the data expected in its lifetime. And it's just getting started.

There are some major mysteries in the universe that scientists hope to answer, and the LHC could be instrumental in some of that progress. Below, let's explore 10 strange corners of the universe that the LHC could explore.

Related: The Large Hadron Collider will explore the cutting edge of physics after 3-year shutdown

The Higgs boson

What is probably the most famous discovery to come out of the LHC to-date, the Higgs boson, is an elementary particle the existence of which was confirmed in 2012 at the LHC. There is, however, still a lot to be learned from studying the strange particle..

First proposed in 1964 by a group of theorists including Peter Higgs and François Englert, the Higgs boson was the last undiscovered particle predicted by the Standard Model, the theory that explains all known fundamental forces and particles in the universe. (In 2013, Higgs and Englert were awarded the Nobel Prize in physics following the LHC's detection of the Higgs boson the year before.)

The Higgs boson was suggested as an explanation for why certain particles have mass. The particle is associated with what is called the Higgs field, which gives mass to other elementary or fundamental particles like electrons and the quarks that make up protons. The particle even gets its own mass from interactions with the Higgs field. 

But not all fundamental particles have mass: The photon, or light particle, has no mass, for example. There remain many mysteries about the Higgs boson and, with future experimentation at the LHC, particle physicists could paint a more complete picture of this strange particle.

LHC scientists have already observed the Higgs particle doing strange things ever since they finally spotted it, offering additional mysteries to solve. In fact, in Run 2 at the LHC, researchers experimented to see if the Higgs boson might decay into dark matter particles (though they did not detect this.)

Dark matter

Scientists hope that with the help of the LHC, they will be able to find particles that constitute dark matter, the never-before-observed stuff that makes up about 80% of all matter in the universe.

Dark matter is a mysterious material that scientists predict makes up over 80% of all matter in the universe. Although dark matter is invisible material, of stars, planets and galaxies. In other words, we can't see dark matter but we know it's there because we can see its effects.

"Dark matter is most of the matter in the universe, and we have no idea what it is. One of the most outstanding questions in all of science is, 'What is dark matter?'" Benjamin Safdi, an assistant professor of physics at the University of California, Berkeley whose research includes investigating possible explanations for dark matter, said in a statement. 

Currently, scientists have a number of different dark matter candidates, strange particles that could be the elusive dark matter. But, while the culprit hasn't yet been identified, the LHC remains a powerful tool that scientists will continue to use to solve this major mystery.

"If the LHC detects a potential dark-matter particle, it will require confirmation from the other experiments to prove that it is indeed a dark-matter particle," CERN officials wrote in a statement. "By contrast, if the direct and indirect experiments detect a signal from a dark-matter particle interaction, experiments at the LHC could be designed to study the details of such an interaction."

Dark Energy

While its name might seem to imply that dark energy is similar to dark matter, their connection lies in the name alone. 

In addition to their similar names, dark energy is also invisible and expansive. Dark energy is a mysterious force suspected to make up nearly three-fourths of the universe, and scientists think it's causing the expansion of the universe is speeding up. 

While the LHC is designed to experiment with particles, some theorists have suggested that if dark energy is a type of force or field, then the LHC could be used to investigate that idea, similarly to how the LHC used the Higgs field to produce the Higgs boson particle, physicist Clare Burrage described to Symmetry Magazine. 

"Cosmologists know that there is new physics we don't understand, and all the evidence is pointing toward something very fundamental about our universe,” Burrage said. "The experiments on the LHC are also very interested in the fundamentals."

Scientists have also suggested that dark energy, if it's a type of field, could produce light-weight particles, Burrage said.

"The main focus of LHC has been heavy particles, so we had to go back and re-interpret the data to look for something light," she added.

WIMPs

In terms of dark matter, one of the candidates that's gotten serious attention over the years has been weakly interacting massive particles, or WIMPs, which LHC has already investigated. 

WIMPs are hypothetical particles that are said to interact via forces including gravity and which might exist outside of the Standard Model.

"The LHC has really broken new ground in the search for dark matter in the form of weakly interacting massive particles," dark-matter theorist Tim Tait of the University of California Irvine involved in the LHC Dark Matter Working Group said in a CERN statement. 

So far, the LHC has attempted to spot this dark matter candidate. Scientists have used the LHC to look for WIMPs by searching for signals of what might be created by, for example, WIMPs interacting with ordinary matter, Tais said. 

But "all of the observed results have been consistent with models that don’t include dark matter," Tait said. However, the data so far gives "us important information as to what kinds of particles can no longer explain [dark matter]."

Even if WIMPs can't explain dark matter, chasing these particles has been fruitful. "The results have both pointed experimentalists in new directions for how to search for dark matter, and prompted theorists to rethink existing ideas for what dark matter could be — and in some cases to come up with new ones," Tait added.

But the door isn't completely shut on WIMPs, and the mystery of what they may or may not be still hangs out there. 

"I still hold a fire for WIMPs," John Ellis, a particle physicist, told Space.com earlier this year. 

Axions

Axions are another hypothetical elementary particle that have been in the spotlight as WIMPs have lost a bit of their luster in the scientific community. The axion, proposed in 1977, has both low mass and low energy; in 2020, physicists found the first direct evidence of axions and fanned the flames of interest in the particle as a dark matter candidate.

Especially with the 2020 findings, the axion is growing in popularity as a dark matter candidate. But no one has yet "caught" an axion by directly detecting the particle in an accelerator like the LHC.

"We suspect it is a new particle we don't know about, and the axion could be that particle," Benjamin Safdi said about dark matter. "It could be created in abundance in the Big Bang and be floating out there explaining observations that have been made in astrophysics."

Scientists have proposed a number of possible experiments that could be used to try and "catch" an axion, but, as researchers described in a 2018 CERN statement, the LHC can be used to search for a new, hypothetical particle: the QCD axion. 

Even though physicists haven't yet "caught" either the axion or this similar variety, it's possible that future experimentation with the LHC might shed new light on this particle mystery, potentially confirming scientists' suspicions about the axion or finding new information that changes existing ideas entirely. 

"Ghost particles"

Neutrinos, nicknamed "ghost particles" because of their elusive nature, were spotted for the first time in a particle accelerator in 2021. The discovery was made at the LHC and was a major breakthrough for physics that has opened up a whole world of subatomic mysteries.

Neutrinos are subatomic particles similar to electrons with no electrical charge and such a small mass that scientists used to think they had no mass at all. Neutrinos are thought to be one of the most prevalent particles in the entire universe; every second, about 100 billion neutrinos pass through every square centimeter of the human body and these particles, produced in the hearts of stars through nuclear fusion, are just about everywhere.

But, because neutrinos don't interact much with matter (neutrinos only interact via gravity and the weak force) and because of their lack of charge and tiny mass, they have been remarkably difficult to spot in particle accelerators. 

LHC's landmark 2021 detection changed that, and with this big "first" accomplished, the LHC can now push this science forward, further exploring these ghostly particles that permeate our universe. 

Supersymmetry

Supersymmetry is a fundamental mystery of the universe that continues to lurk in the back of scientists' minds. 

Simply put, supersymmetry is a theory suggesting that all of the universe's fundamental particles should have counterpart theoretical "superparticles." This theory, which is an extension of the Standard Model, says that when elementary particles (like photons or electrons) were formed at the beginning of the universe, they were created alongside matching "superparticles." The theory suggests that every particle seen in the Standard Model has a partner particle that spins differently. 

However, there has been no concrete, direct evidence of supersymmetry. 

Scientists hope that, by using a facility like the LHC, as astrophysicist Paul Sutter has explained, scientists could essentially recreate the conditions of the early universe and search for signs of supersymmetry. 

"If the theory is correct, supersymmetric particles should appear in collisions at the LHC," CERN said in a statement. Scientists have previously wondered whether the LHC is creating supersymmetric particles that are escaping the detector then decaying. And since experiments at the LHC like ATLAS, the largest general-purpose experiment at the LHC, detect particles' decay and the products of that decay rather than the particles directly, physicists remain concerned about how these particles could be detected if they are indeed there. 

But with this mystery lingering, it makes new opportunities for exploration with the LHC all the more exciting. 

The matter-antimatter problem

One of the biggest mysteries in science remains what is known as "matter-antimatter asymmetry."

As we understand it, the Big Bang should have created nearly equal amounts of matter and antimatter in the early universe. (Antimatter particles have the same mass as their counterpart matter particles, but with an opposite electric charge.) But the universe today appears to be primarily composed of matter, with very little antimatter. This mystery asks: what happened? 

Scientists believe that the Big Bang created a "nearly" equal amount of antimatter and matter because if there was the exact same amount, the two types would have essentially canceled one another out, leaving behind an empty universe, CERN has described.

But that slight asymmetry between matter and antimatter at the Big Bang isn't fully explained by the Standard Model and physicists are also unsure how this slight asymmetry led to the matter-dominated universe that we live in today.

With the LHCb (Large Hadron Collider beauty) experiment, scientists have investigated slight differences between matter and antimatter. Most recently, earlier in 2022, the largest matter-antimatter asymmetry was observed with this experiment. Future investigation could reveal new details about why and how our universe came to be. 

Mystery particles

If the world's largest and most powerful particle accelerator is good at one thing, it's smashing particles together. This technology has enabled incredible steps forward in the field of particle physics, including creating and observing strange, new particles that scientists had only suspected might exist.

From 2011 to 2021, scientists using the LHC discovered 59 new types of hadron particles. Among those, in 2018, was a strange "mystery particle"; in 2021, a rare four-quark "tetraquark" particle, a non-elementary particle, was spotted at the LHC. And, of course, the Higgs boson discovery at the LHC certainly counts as a remarkable particle find. 

As researchers continue to smash protons near the speed of light and explore the fringes of what we know to be true about the universe, it's likely that strange, new particles will continue to pop up during the LHC's new operational phase. 

The Standard Model

The last item on this list is almost an honorable mention, but it remains one of the most significant, all-encompassing objectives that scientists use the LHC to investigate.

The Standard Model describes all known forces and particles in the universe; it's the best "theory of everything" that scientists have to work with. But the Standard Model isn't complete and, as we explore major unknowns like dark matter and dark energy, researchers continue to explore how they might need to extend the Standard Model. 

The LHC, allows scientists to both confirm what we already suspect about the Standard Model and also see where the model falls short, whether physicists may need to extend the theory or break the model apart altogether.

Email Chelsea Gohd at cgohd@space.com or follow her on Twitter @chelsea_gohd. Follow us on Twitter @Spacedotcom and on Facebook.

ATLANTA — While scientists still don't know what makes up the mysterious dark matter thought to dominate the universe, a new study of dwarf galaxies orbiting the Milky Way presented here Sunday (April 1) at the American Physical Society has chipped away at the possibilities, offering intriguing hints about the nature of dark matter.

Dark matter is the name given to whatever makes up roughly 80 percent of the mass in the universe, holding galaxies together and exerting its gravitational force on regular matter. Yet dark matter is also invisible and, so far, impossible to directly detect.

One way astronomers aim to study the elusive stuff is by looking at its effects on observable things.

For example, one theory suggests that dark matter is made of exotic particles called WIMPS (weakly interacting massive particles). Sometimes, these particles should encounter their antimatter partner particles, anti-WIMPS, and the two should annihilate each other as matter and antimatter always do.

This annihilation would produce radiation in the form of high-energy gamma-rays that telescopes should be able to observe.

The recent study used NASA's Fermi Gamma-ray Space Telescope to search for these gamma-rays in the small dwarf spheroidal galaxies that orbit the Milky Way.

"Dwarf spheroidals are some of the most dark matter-dominated objects in the universe, and these objects are not expected to be emitting gamma-rays from anything other than dark matter," astrophysicist Jennifer Siegal-Gaskins of Caltech said here Sunday (April 1) at the meeting. "This means they're very clean targets for gamma-ray signals from dark matter." [Gallery: Dark Matter in the Universe]

Siegal-Gaskins and her colleagues analyzed 12 of these mini galaxies orbiting the Milky Way, and found basically no gamma-rays.

The result means that if dark matter is made of WIMPS, the particles don't annihilate with their antimatter counterparts very often. That reduces the varieties of WIMPS that could explain dark matter.

"For the first time, we're now starting to prove the combinations of particle parameters that are favored by cosmology," Siegal-Gaskins said. "We're really starting to probe the really interesting theoretical models of dark matter."

One property of microscopic particles is called cross section, which can be thought of as the area of the particle, predicting how often it will collide with other particles. Fermi's lack of gamma-ray sightings in the dwarf galaxies means that if dark matter is made of WIMPS, they can't have some of the cross-section values that conventional models have predicted.

The researchers hope that continued observations of more of the Milky Way's dwarf galaxies could help eliminate further possibilities for dark matter, helping to corner the elusive particles.

"This study is based on two years of data," Siegal-Gaskins said. "In the next few years, it's quite possible that more dwarf spheroidal galaxies of the Milky Way will be discovered. We have the potential to push that limit even lower. I think we have a lot of exciting prospects."

You can follow SPACE.com assistant managing editor Clara Moskowitz on Twitter @ClaraMoskowitz. Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.