Category: Dark Universe

Black holes more massive than entire galaxies are not a major component of the mysterious dark matter that's thought to make up most of the matter in the cosmos, a new study finds.

For decades, to explain why galaxies do not spin apart at the speeds at which they whirl, scientists have suggested the existence of an unseen substance known as dark matter, whose gravitational pull helps keep galaxies together. Dark matter is thought to make up about five-sixths of all matter in the universe.

Much remains unknown about dark matter, however — including whether or not it actually exists. Black holes make good potential contenders for dark matter, since they are extremely massive and are difficult to spot in the dark depths of space.

In the new study, researchers investigated whether dark matter could be made of "stupendously large black holes," ones with masses greater than 100 billion times the mass of the sun. Stupendously large black holes greater than 1 million billion to 10 million billion suns in mass would be heavier than entire galaxies.

So far, astronomers have not detected any stupendously large black holes — currently, the largest black hole known may weigh about 36 billion suns. Since researchers have not seen any even after looking at many galaxies, the new study noted they cannot make up all of dark matter — but team members wondered if the exotic objects still might constitute a significant portion of the puzzling substance.

Often, dark matter is thought of "as a fine dust spread everywhere," study co-author Christopher Gerlach, a theoretical physicist at the Mainz Institute for Theoretical Physics in Germany, told Space.com. However, if dark matter is packed into a handful of gigantic objects such as stupendously large black holes, "the universe becomes grainy on very large scales. And we can check that."

Specifically, the scientists analyzed the light from the dawn of the universe, study co-author Yann Gouttenoire, a theoretical physicist at the Mainz Institute for Theoretical Physics, told Space.com.

For the first 380,000 years after the Big Bang, the cosmos was filled with a hot plasma in which light was trapped. Eventually, the expansion of the universe let the cosmos cool enough for the plasma to largely dissipate and form atoms. This in turn let light shine freely, "and that light is still arriving today," Gerlach explained. "We call it the cosmic microwave background, a snapshot of the infant universe covering the whole sky."

The temperature of the cosmic microwave background "varies from place to place by about one part in 100,000," study co-author Antonio Iovino, a theoretical physicist at New York University, Abu Dhabi, in the United Arab Emirates, told Space.com. "That pattern tells us how matter was spread back then."

Analyzing the cosmic microwave background revealed it is not grainy the way stupendously black holes would have made it. "So these black holes can't be a significant part of the dark matter," Nicholas Leister, a theoretical physicist at the Mainz Institute for Theoretical Physics, told Space.com.

The researchers cautioned that the new findings do not suggest that stupendously large black holes cannot exist, only that they do not make up a major fraction of dark matter. They added that another candidate for dark matter — relatively tiny black holes the size of asteroids — might potentially exist. They are now investigating whether they can rule out such itty-bitty black holes as a major constituent of dark matter.

The scientists detail their findings in a study that will be published Oct. 26 in the journal Physical Review Letters.

Hydrogen may be the most common element in the cosmos, but scientists could use it to do something unique: uncover the nature of dark energy, the mysterious force driving the accelerating expansion of the universe.

This new line of dark energy investigation comes from the fact that researchers have determined that the CHIME (Canadian Hydrogen Intensity Mapping Experiment) project can detect the faint radio glow of hydrogen from the universe's distant past.

Not only does this represent a faster and much less expensive way to investigate dark energy, but it is a major milestone for CHIME. The instrument was specifically devised to investigate dark energy and its pervasive influence.

"This is a completely new technique for probing the cosmos, delivered by an instrument that was conceived and built by Canadians," CHIME principal investigator Mark Halpern of the University of British Columbia said in a statement. "It's a bold new step in the global cosmology program and a Canadian success story."

Why is dark energy so problematic?

Dark energy is the mysterious force that is accelerating the expansion of the universe. It is so problematic for scientists because it started acting on the fabric of space only after the expansion triggered by the Big Bang had halted.

That's akin to pushing a child on a swing, watching it stop, and then seeing the swing start up again without a push. And, not only that, but the swing starts oscillating faster and faster. Consider scientists akin to very worried parents, who would really like to know where this ghostly push came from and how it is going to proceed.

Just as, if the push on the swing continues, the child could end up in the bushes, or in orbit, the strengthening of dark energy could result in the cold death of the cosmos, or even a "Big Rip" scenario that sees space shredded. Alternatively, if it weakens and allows gravity to reassert dominance, then the universe could collapse back in on itself, resulting in a "Big Crunch" ending that sees the cosmos compressed back into a singularity, as it was at the beginning of time.

Dark energy is now the dominant element of the universe, accounting for 68% of the universe's matter-energy budget. It's little wonder that scientists are very keen to know what this mysterious force is.

So how can hydrogen help the investigation of dark energy?

"Hydrogen is the most common element in the universe and the raw material from which stars form," team member Arnab Chakraborty of the University of Toronto said. "Its faint radio emission acts like a cosmic tracer, revealing how matter is distributed across space."

Previously, CHIME could map the distribution of hydrogen in the early universe but only by cross-correlating its observations with galaxy survey data from other telescopes, operations that cost millions of dollars and can only focus on regions of the universe dense enough to form stars. CHIME has now shown it can map the radio glow of hydrogen all on its own.

Indeed, the team has already begun making steps in this direction using just a tiny fraction of existing CHIME data. Using 94 nights of observations from 2019, they detected a hydrogen signal from when the universe was just 5 billion years old.

"Our data indicate that roughly 2% of the hydrogen in the universe was in neutral atomic form at this time, broadly consistent with other measurements," team member Shabbir Shaikh of Arizona State University said. "By measuring how that hydrogen is distributed and clustered, CHIME gives us a new way to test our understanding of how galaxies form and evolve."

CHIME has now collected seven years of data, and using this, the team is hoping to probe the distribution of hydrogen back to 3 billion years after the Big Bang.

The team's research was published across two papers in The Astrophysical Journal.

A catalog of almost 3,000 white dwarfs that exploded as type Ia supernovas after overfeeding on companion stars indicates that dark energy, the mysterious force accelerating the expansion of the universe, is changing over time.

The discovery, in conjunction with data from the Dark Energy Survey (DES), backs results revealed from the Dark Energy Spectroscopic Instrument (DESI) published in 2024 that suggested dark energy's influence is weakening.

That means that the team's research doesn't just involve the most comprehensive catalog of type Ia supernovas; it presents the clearest picture yet of the evolution of the universe and the influence of dark energy.

"We've rebuilt 3 decades of astronomical observations into a single, consistent framework," team member Ryan Camilleri of the University of Queensland said in a statement."We combined our data with other cosmic measurements, including relic light from the Big Bang and maps of how galaxies are distributed through space.

"Instead of confirming the standard model of cosmology, which assumes dark energy is fixed and unchanging, we have more evidence that dark energy may change over time."

How do exploding white dwarfs tell us about dark energy?

White dwarfs are the smoldering stellar remnants that are left over when stars with around the mass of the sun exhaust the fuel for nuclear fusion in their cores. This ends the outward pressure that supports a star against its own gravity, meaning the star's core collapses as the outer layers are shed. The core becomes a white dwarf, and for single stars, that is the end. But around 50% of sun-sized stars have a binary companion, and this can lead to renewed activity and a change in the star's fate.

If the white dwarf and its companion are close enough together, the dead star begins stripping away the outer layers of its companion. As this material builds on the white dwarf, it pushes the stellar remnant's mass over the so-called Chandrasekhar limit, allowing it to go supernova.

These cosmic explosions are called type Ia supernovas, and their light output is so uniform that these events are referred to as standard candles. They are of vital importance because measuring how their light has been redshifted as it travels means type Ia supernovas can be used to measure cosmic distances.

"Over the years we've learned a lot more about how supernovae behave so we've been able to go back and apply that improved understanding to older data," Camilleri said. "Extensive work has been done to link observations from different telescopes with different capacities and take into account issues such as cosmic dust and galaxy mass which can affect the light coming from a supernova.

"We also incorporated more subtle effects such as gravitational lensing, which is the bending and magnification of light around large objects as it travels from a supernova to Earth."

Combined with the 2024 results from DESI, this research could change our idea of what dark energy actually is.

"Our supernova data from DES in 2024 first showed hints that dark energy may be time-varying, and this new compilation also sees a deviation from the standard model, although in a slightly different direction," Davis said. "Similarly, results from DESI found hints of variations in dark energy in its surveys of relic sound waves from the early universe.

"So, two completely independent measurements have found hints of time variation in dark energy, challenging the standard model that dark energy doesn't change."

Davis added that, as well as revealing what dark energy actually is, this research may also hold the clue to explaining how gravity and quantum physics fit together. While quantum physics (the best theory we have of how the universe operates at subatomic scales) and Einstein's theory of general relativity (our best picture of gravity) have been highly successful in their own rights, scientists have so far been unable to unite them. In other words, there is no theory of quantum gravity.

“We know these two theories are each immensely successful in their own realms, so if we can figure out how to put them together, that would be a huge step in theoretical physics," Davis continued.

This effort will receive a boost when data is added to the team's already comprehensive type Ia supernova catalog. This will include observations from the Dark Energy Bedrock All-Sky Supernova program (DEBASS), which is detecting hundreds more local supernovas than even the DES survey.

The team's results are available on the repository site arXiv.

In what could be a groundbreaking discovery, scientists report they may have detected the first direct evidence of dark matter. The potential detection came from the LUX-ZEPLIN experiment, in the form of a single suspected interaction between a Weakly Interacting Massive Particle (WIMP), one of the leading hypothetical particle candidates for dark matter, and an everyday particle.

Dark matter has been a headache for scientists because, despite accounting for 85% of the mass in the universe, scientists have no idea what it is. The fact that dark matter doesn't interact with electromagnetic radiation, or light, means that it can't be composed of electrons, protons, and neutrons, the particles that make up the atoms that compose stars, planets, moons, our bodies, and everything we see around us on a day-to-day basis.

This has spurred on the search for new types of particles beyond the limits of the so-called Standard Model of Particle Physics. So far, this search has been frustratingly fruitless — but the LUX-ZEPLIN experiment may have finally caught a glimpse.

An analysis of data from LUZ-ZEPLIN, a detector composed of 10 tons of ultrapure liquid xenon, one mile underground at the Sanford Underground Research Facility (SURF) in South Dakota, showed a single particle interaction that scientists can't explain with known background signals from normal matter.

"This was a detailed study in a region we hadn't explored within this dataset, and we spent months of additional effort to understand all the possible causes of background events," team leader Sam Eriksen of the University of Bristol in the U.K. said in a statement. "We understand our detector and the backgrounds so well that even a single outstanding event, like the one we found, is important."

What does this tell us about dark matter?

If the event detected by this team was caused by the rare interaction between two WIMPs, this would tell scientists some things about these currently hypothetical particles.

Firstly, the signal indicates that WIMPs have a mass around 200 times greater than the mass of a proton. It also suggests that WIMPs would interact with ordinary matter in a way that hasn't been predicted by the simplest modelling of these particles before.

Of course, these results are not definite yet. This one potential detection isn't statistically significant enough to confirm that what has actually been detected is an interaction between a WIMP and an everyday matter particle. There still remains a 0.5% chance that the event could be explained by known backgrounds.

As LUX-ZEPPLIN continues to gather the largest dataset in dark matter science, the team will determine if this event has grown in significance or if its significance fades.

One definite positive is the fact that WIMP/ matter interactions are so rare that it wouldn't take many detections such as this to confirm the existence of WIMP dark matter, thus solving the puzzle of what the universe's most mysterious stuff actually is composed of.

"We expect dark matter events to be extremely rare, so only a handful could mark the first detection of WIMP dark matter," Eriksen said.

The team's results were presented at the 2026 TeV Particle Astrophysics conference and have been submitted to the journal Physical Review Letters.

New research suggests that if dark matter is composed of "dark photons," it would not have heated the early cosmos like scientists previously thought. If correct, this discovery could represent a paradigm shift in the hunt for the universe's most mysterious stuff.

Dark matter remains so elusive because, despite outweighing the everyday matter that composes stars, planets, moons and our bodies by a ratio of five to one, it is effectively invisible. That is because it doesn't interact with light. And the fact that electrons, protons, and neutrons do interact with light (or, more accurately, electromagnetic radiation) has inspired the search for particles beyond the Standard Model of particle physics, leading to lots of hypothetical candidates for dark matter.

One of these candidates is the dark photon, the dark universe's version of a photon carrying a force other than electromagnetism, which is the responsibility of standard photons.

When dark photons have been considered in the past, scientists have concluded that they would have transformed into ordinary photons while still embedded in the thick and dense soup that filled the early cosmos. This would have further heated this already blisteringly hot plasma and left detectable traces of dark photons.

This severely limits the search parameters in which dark photons could exist — so much so that many cosmological observations rule out the existence of dark photons.

Now, new computer simulations show that the dismissal of dark photons may have been a little hasty. The conversion of dark photons to photons would have shut off before significant heating could occur.

That brings previously excluded search parameters back into play.

"These exclusions were saying the strength of dark matter had to be 10^8 times weaker than it actually can be," team member Anson Hook at the University of Maryland said in a statement. "This paper opens up a lot of new possibilities to look for dark matter."

The team behind this research first saw hints that the transformation of dark photons to photons may not be as straightforward as scientists had assumed when they realized the amount of energy involved is suspiciously large. The problem, they began to suspect, was the fact that this process had been considered to be linear; in other words, the energy released gradually and steadily converts to plasma.

"The treatment for the last 15 years is a linear treatment. If you use that approximation, you can compute the amount of energy transfer, and it's very large," team member Junwu Huang of the Perimeter Institute said in the statement. "And I realized it's not possible."

Performing their first computer simulations, Huang and colleagues realized that the linear process fails to paint a complete picture.

"What we realized is that, as you are converting energy into the Standard Model plasma, the plasma actually goes crazy," Huang said. "There are a lot of nonlinearities in the system, and these nonlinearities basically shut off the energy conversion after a tiny amount of energy is converted."

The research represents a major widening of the parameters in which dark photons could exist, expanding this metaphorical hunting ground considerably. In fact, it could also impact the hunt for hypothetical particles beyond the Standard Model of particle physics.

"By calculating the early universe plasma correctly, experiments will probe new parameter spaces and potentially actually see something," team member Mohamad Shalaby of the Perimeter Institute said in the statement.

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

Two major mysteries in science, the nature of dark matter and the possible existence of higher dimensions, could be linked, new research suggests. The team behind a new study proposes that dark matter may be so strange and ghost-like because it is in tune with a fifth dimension.

When scientists discuss "extra dimensions," they aren't talking about other universes in which another evil version of you exists (and with a beard). Instead, they refer to dimensions that could be "curled up" with reality alongside the standard four-dimensional spacetime, consisting of the three dimensions of space and one dimension of time.

While these extra dimensions remain highly speculative, they have become a hot topic, especially as string theory, the most popular extension to standard physics, relies upon the existence of at least 11 dimensions. Scientists are more sure that dark matter exists, but proving its existence still remains troubling because, despite its gravity literally holding galaxies together and outweighing ordinary matter by around five to one, it remains effectively invisible because it doesn't interact with light and it simply ghosts through ordinary matter.

"Understanding dark matter would represent a profound advance in humanity's knowledge of the cosmos and what it is made of," team member Yu-Dai Tsai of the University of Sheffield said in a statement.

"Our research gives physicists clear new targets in the search for dark matter, while connecting two of the biggest ideas in fundamental physics: the mystery of dark matter and the existence of hidden dimensions."

Dark photons play dark matter like a violin

Though the main idea is that dark matter may operate in the fifth dimension, this new research expands upon that concept with another theory. It suggests that dark matter exists with another inhabitant of the fifth dimension, a force-carrying particle called a "dark photon."

Standard photons are the constituent particles of electromagnetic radiation, or light; dark photons would be similar but for a hypothetical "dark force."

The team's new proposal would see the unique geometry of the fifth dimension causing the masses of dark matter particles to form an arrangement that gives rise to a "dark matter resonance." This is akin to the intense vibration of a musical instrument at certain notes.

"Dark matter resonance is already known to be a powerful idea, with the potential to change our understanding of how dark matter was produced in the early universe and how we search for it today," team member Yu-Dai Tsai of the University of Sheffield said in a statement. "But many previous resonant dark matter models have treated the resonance as an assumption. This work gives a possible deeper origin for it: the resonance may come directly from the geometry of hidden dimensions."

Tsai explained that while dark matter resonance is a phenomenon that has been explored before, the research conducted by this team differs because it suggests dark matter resonance is not a coincidence. Instead, the possible deeper origin for the resonance sees it emerge directly from the geometry of hidden dimensions. This would allow dark matter to interact strongly shortly after the Big Bang while allowing it to settle into its ghost-like inert existence today.

"This resonance can make dark matter interactions much stronger at crucial epochs in cosmic history, such as in the early universe," Tsai added. "Crucially, the model allows for these strong interactions in the past while still explaining why dark matter appears so inert and hard to detect today."

Of course, it is very early days for the team's theory, but it excitingly offers a way toward solving two of the universe's greatest mysteries.

The team's research was published in the Physical Review D.

The expansion of the universe is still accelerating under the influence of dark energy, despite recent claims to the contrary, according to new research. This means that dark energy, the mysterious force that dominates the universe, is not weakening but continues to get stronger, considered something of a "cosmological crisis" as it was so against expectations.

In 1998, via the study of cosmic explosions called Type Ia supernovas, astronomers discovered that not only is the universe expanding, but that the speed of that expansion is increasing. "Dark energy" was the name given to the mysterious force driving this accelerating expansion. Since then, scientists have discovered that dark energy accounts for around 70% of the universe's matter and energy.

In November 2025, research was published that suggested the expansion of the universe was slowing, meaning dark energy would be weakening. But this new research suggests that these findings from last year might not be a cosmic hand grenade thrown into the cosmological apple cart, but instead may have actually emerged from a scientific misunderstanding.

"Thankfully, we have averted this crisis, but the mystery about why the rate of expansion of the universe is still accelerating remains," lead author of the new refuting research, Phil Wiseman, from the University of Southampton in the UK, said in a statement. "The previous and well-accepted measurements were, in fact, fine, and our current understanding of the fate of the universe remains robust. By proving our measurements are correct, we can get back to trying to understand what this dark energy actually is, rather than wondering if it exists at all."

The research from 2025 that suggested dark energy was weakening was based upon a reassessment of the brightness of Type Ia supernovas, which occur when a dead star called a white dwarf overfeeds on a companion star. This causes a runaway nuclear explosion of such uniform brightness that it can be used to measure cosmic distances. In fact, these explosions are so uniform that astronomers refer to them as "standard candles."

This prior research determined, incorrectly it now seems, that as the universe has aged, the brightness of Type Ia supernovas had changed, leading to incorrect measurements of distances based on them as well as incorrect estimates of the speed of the universe's expansion. Both of these led to the suggestion that dark energy is weakening.

But Wiseman and colleagues found this previous team had made an error in how they calculated the ages of exploding white dwarfs, finding they had assumed the ages of these stars would be the same as the ages of the galaxies in which they exploded.

They also found the 2025 research hadn't accounted for a common correction used in cosmology that factors in the masses of galaxies in which Type Ia supernovas occur.

"Extraordinary claims require especially careful testing," team member Adam Riess, who in 2011 shared the Nobel Prize for the discovery of dark energy, said. "What we find is that when we calibrate these supernovae, accounting for different host environments and populations, the evidence for cosmic acceleration remains remarkably consistent."

While the challenge to dark energy's growing dominance over the universe seems now to have been refuted, the back and forth on this topic shows how ideas in science aren't dogma and remain open for revision.

"This is how progress is made," team member Mark Sullivan, also from the University of Southampton, said. "Although this idea did not turn out to be correct, it has opened up new ways of thinking about how supernovae explode and how we can measure dark energy more accurately."

The team's research was published on June 10 in the journal Monthly Notices of the Royal Astronomical Society.