Category: black holes

Though their origins may be shrouded in mystery, fast radio bursts (FRBs) could be used to probe some of the universe's biggest puzzles. This includes probing the nature of dark matter, the invisible sort of matter that somehow dominates the universe, and dark energy, the mysterious force causing the expansion of our universe to accelerate. They could even shed light on the mysteries of neutrinos, or "ghost particles." Let's dive into how.

FRBs are brief but intense blasts of radio waves currently thought to erupt from rapidly rotating dead stars with the universe's strongest magnetic fields, called magnetars. As FRBs travel billions of light-years to reach Earth, they pass through dense clouds of gas and dust in galaxies. This "cosmic fog" changes the original FRB signal. What this means is these blasts of radio waves carry the fingerprints of how matter in the universe is distributed.

Mapping the distribution and "clumpiness" of ordinary matter in galaxies can then help trace the distribution of dark matter, the effect of dark energy and the mass of neutrinos.

"We've established that FRBs are a leading probe of the distribution of matter in the universe," team leader Kritti Sharma, a graduate student working with Vikram Ravi, a professor of astronomy at the California Institute of Technology (Caltech) and also part of the team, said in a statement. "These FRB data can be used to enhance cosmology experiments that are trying to answer questions about dark matter, dark energy, and the mass of neutrinos."

For this research, Ravi and Sharma analyzed a sample of about 100 FRBs. This represents the first time scientists have used FRBs to directly measure the impact of so-called "feedback" from galaxies on the clumpiness of matter in the large-scale regions between galaxies.

Cosmic ghosts and the dark universe

Ordinary matter, composed of atoms made up of electrons, protons and neutrons, accounts for just around 5% of the universe's energy/matter budget despite comprising stars, planets, moons, our bodies, next door's cat and everything we see around us on a day-to-day basis.

Of this budget, the other 95% is composed of dark energy (68%) and dark matter (27%). It's little wonder that scientists are very keen to better understand these two aspects of the cosmos, sometimes collectively referred to as the "dark universe."

Things get even more murky when considering how, of that 5%, the second most abundant particles in the universe, aside from particles of light or photons, are neutrinos. These get their nickname of "ghost particles" because they interact with other matter particles so infrequently that approximately 100 trillion neutrinos pass through your body every second without leaving any trace. This is possible because neutrinos are virtually massless, and scientists are keen to accurately measure the mass of these cosmic ghosts.

These three mysterious elements of the cosmos have played a vital role in the evolution of large-scale cosmic structures like galaxies and galaxy clusters. That means, in turn, that measuring the clustering of matter can reveal details about the aspects of the universe that influenced that clustering.

However, to do that, scientists also have to understand how other factors smooth out cosmic clumpiness. That includes the energy pumped out from the hearts of galaxies by feeding supermassive black holes, a type of cosmic feedback that smooths out clumpy cosmic matter lying outside galaxies.

"The feedback process thins the gas around the galaxies, redistributing matter across vast distances. It smooths out clumps of matter in a way that looks astonishingly similar to what massive neutrinos do, or what dark energy or dark matter theories predict," Ravi said. "Unless scientists can independently measure this contribution from feedback, they can't tell these effects apart."

That's where FRBs come in.

The researchers found that, while galactic feedback does indeed smooth surrounding material, making it less clumpy, the effect is weaker than has previously been measured.

"Our analysis of FRBs reveals how gas ejected by astrophysical feedback suppresses cosmic structure," team member Elisabeth Krause of the University of Arizona said in the statement. "This is amazing considering we only had about 100 FRBs in our sample. It's only the beginning."

The investigation of the universe with FRBs could get a major boost in 2029 when Caltech's Deep Synoptic Array (DSA) begins operating in Nevada. This powerful radio telescope is expected to find tens of thousands of FRBs, a major boon for cosmology.

The team's research was published on Tuesday (Sept. 8) in the journal Nature Astronomy.

A "forbidden" merger between two massive black holes may not have been quite as impossible as previously thought. That's according to new research that suggests the black holes involved were smaller than expected.

On Nov. 23, 2023, the gravitational wave detector LIGO (Laser Interferometer Gravitational-Wave Observatory) detected tiny ripples in spacetime caused by the merger of two black holes. What was incredible about this signal, designated GW231123, was that it seemed to be the result of a black hole with 140 times the mass of the sun colliding with another that holds 100 solar masses.

This raised eyebrows among researchers because usual models of stellar evolution struggle to account for such massive black holes, especially ones that seemed to be spinning as fast as these two. While scientists have been attempting to explain how such an odd black hole binary could form. The team behind this new research suggests it doesn't need to be explained at all. They think that the masses of these black holes were an illusion.

The key to this illusion is a phenomenon called gravitational lensing, first predicted by Albert Einstein's 1915 theory of gravity, general relativity, which also first predicted the existence of gravitational waves. This theory says objects with mass cause the curvature of space and time, united as a four-dimensional entity called "spacetime." The more mass an object possesses, the greater the curvature, and because gravity arises from this curvature, the greater the gravitational influence.

Gravitational lensing occurs when light from a background object passes a massive foreground object. The foreground object can warp the fabric of spacetime in such a way that the light's path is curved. This means light from the same background source can reach Earth at different times, depending on how much that light was diverted.

This difference in travel time can magnify a background source, and it has been used to great effect to observe distant and ancient galaxies ordinarily too faint to be seen.

This research team thinks the effect also applies to gravitational waves, suggesting the signal GW231123 is an example of gravitationally lensed ripples in spacetime that made the black holes appear larger than they actually are.

"Like light, gravitational waves can also be deflected, magnified and split into multiple signals by massive objects," team member Miguel Zumalacárregui, group leader in the Astrophysical and Cosmological Relativity Department at the Albert Einstein Institute (AEI), said in a statement. "For gravitational waves, diffraction and interference effects give us an additional way to identify and study lensed signals."

To investigate this possibility, the team developed a mathematical model of gravitational lensing and created software powerful and fast enough to analyze it.

"If we assume that GW231123 was deflected and distorted by a compact object of about 190 to 850 solar masses — or by an extended structure such as a globular cluster — we can understand the observed high masses," said team member Srashti Goyal, who was based at the AEI when conducting the research. "Moreover, the lensing interpretation does not require unusually high spins."

When the team modeled the event with that consideration factored in, they found the merger involved a system with a mass of 140 solar masses, rather than the 240-solar-mass system initially theorized.

The team doesn't quite know what massive object is responsible for lensing the gravitational wave signal GW231123. But no matter what it is, if the team is correct, the lens could be something quite special.

"The nature of the lens remains a major mystery in our analysis, as individual compact lenses with 100 to 1,000 solar masses should be exceedingly rare," Zumalacárregui said. "Future work will need to establish whether such lenses can form, or whether an ensemble of lighter objects, including stars, can explain this event."

The team can't yet conclusively say if GW231123 is the first gravitationally lensed gravitational wave signal. Finding future signals of the sort will require upgrades to the sensitivity of detectors like LIGO.

Though even before that happens, the research does point to the utility of gravitational wave astronomy to study some of the universe's most violent events.

The team's research was published on August 25 in the Astrophysical Journal Letters.

In the four years that the James Webb Space Telescope (JWST) has been making observations of the early universe, it has been delivering one scientific milestone after another. However, the $10 billion telescope has also left astronomers with a massive problem  — literally.

The JWST has been routinely spotting supermassive black holes in the early universe that, at hundreds of millions of times the mass of the sun, are too big to have grown to such monstrous sizes before the universe was even 1 billion years old. These cosmic titans are also too massive in comparison to the masses of their small host galaxies, challenging what astronomers know about the relationships between supermassive black holes and their galactic homes that are usually observed in the modern universe.

Now, new research suggests this isn't such a massive problem after all. The team behind this research thinks that it is all a matter of perspective, and that these early supermassive black holes aren't as monstrous as scientists have estimated.

"We estimate masses of roughly one to ten million solar masses, compared with the tens or hundreds of millions previously inferred," team leader Alessandro Trinca of the Italian National Institute for Astrophysics (INAF) Astronomical Observatory of Rome told Space.com. "These are still enormous objects, comparable to the four-million-solar-mass black hole at the center of the Milky Way, or a few times larger, but they lie at the lower end of the supermassive black hole population rather than among the most extreme examples.

"Importantly, these masses are much more consistent with the small galaxies that host them."

The answer to this puzzle may lie in missing X-rays

While considering the mystery of "overmassive" black holes in the early universe, Trinca and colleagues picked up on another puzzle associated with these objects.

To reach such sizes, these black holes must be voraciously feeding on surrounding gas and dust. Such feeding black holes and the cosmic larders of gas and dust that surround them are usually extremely bright emitters of X-rays. But this doesn't seem to be the case with the supermassive black holes in the early universe seen by the JWST. The team looked at 14 X-ray-silent supermassive black holes, finding that there is another way of considering this lack of emission.

"Almost none of them are detected in X-rays, even in very deep observations with NASA's Chandra X-ray Observatory," Trinca said. "We interpreted this lack of X-rays as a clue rather than a problem. By incorporating it into our analysis, we find that these objects are likely much less massive than previously estimated. This brings their estimated masses into better agreement with the properties of their host galaxies."

This led Trinca and the team to another conclusion: these early supermassive black holes may not be as massive as previously theorized, but they are feeding even more rapidly than was thought.

If feeding supermassive black holes blast out a lot of X-rays, then it might seem somewhat counterintuitive that ravenously feeding black holes could be X-ray "quiet."

Trinca explains that this apparent contradiction is related to what happens when a black hole accretes matter at extremely high rates. The disk of gas around the black hole becomes geometrically thick, forming a donut-like structure with a narrow funnel along the rotation axis. The hot inner region that would normally produce strong X-rays becomes surrounded by this thick disk.

"As the X-rays escape, they are repeatedly scattered by the surrounding gas, losing energy before they can emerge. As a result, the black hole appears much fainter in X-rays than we would normally expect," Trinca continued. "Therefore, the lack of X-rays is not unexpected in this scenario; it is actually a prediction of the model.

"In addition, this very high feeding might help explain how these black holes could already have grown to millions of times the sun's mass when the universe was only a few hundred million years old."

Out-eating Eddington

One of the reasons that supermassive black holes are so troubling in the early universe is the fact that they grow by consuming matter and through merging with other black holes. However, there exists a limit to how rapidly a black hole, or any astronomical body, can gather or "accrete" matter.

Called the "Eddington limit," this exists because the more matter a body accretes, the more radiation it blasts out. So as the disk around a feeding black hole gathers enough mass to feed a rapidly growing black hole, it should emit so much radiation that it pushes away more matter, preventing it from being replenished.

Eventually this cuts off the food supply to the black hole and curtails its growth. However, this research suggests that supermassive black holes can enter brief phases of "super-Eddington" feeding.

"If these black holes are up to thirty times less massive than previously estimated, there is much less mass to build up within the available time, and their growth history becomes much less extreme," Trinca said. "Instead of requiring continuous, uninterrupted growth over hundreds of millions of years, the picture becomes one of shorter episodes of very rapid accretion, which is exactly the kind of behavior we might expect in the gas-rich and dynamically active galaxies of the early universe."

Confirming the team's theory about bouts of extreme feeding for supermassive black holes will require astronomical evidence, which may be tough to obtain at least for now.

"The most direct test would be to study similar objects that are accreting very rapidly but are located at lower redshifts, where we can observe and characterize their environments in much greater detail. However, such objects are quite rare," Trinca said. "For the more distant population observed with JWST, future missions providing deeper X-ray observations and improved spectra will be of crucial importance and might potentially detect the weak X-ray emission predicted by this scenario."

The INAF researcher added that in the longer term, obtaining direct and independent measurements of black hole masses at progressively earlier cosmic times will provide the strongest test of the team's theory. For now, the research is a striking example of what scientists can do when they don't detect something, rather than when they make a positive detection.

"What was interesting was seeing how much information could be extracted from something we did not observe," Trinca concluded. "A non-detection may appear to be the least informative type of observation, but in this case the absence of X-rays provided a strong constraint and helped define the physical picture more clearly than the detections alone."

The team's research was published in the June edition of the journal Astronomy & Astrophysics.

Some stars encounter supermassive black holes and live to tell the tale. New research shows why the flares these encounters cause dim over repeated episodes, and it may be down to the way these stars spin and an escaping binary partner that leaves them to be a stellar snack for a black hole.

Some stars are unfortunate enough to encounter the supermassive black holes that sit at the heart of every galaxy, being subjected to immense tidal forces that turn them into a strand of stellar spaghetti, a process called "spaghettification." This plasma pasta wraps around the black hole and is gradually fed to it, with some former star stuff being ejected as near-light-speed jets. These occurrences are called tidal disruption events (TDEs).

However, other stars get a reprieve, passing close enough to a supermassive black hole for the cosmic titan to take a bite and strip off material, but not close enough to be fully destroyed. As the star orbits the supermassive black hole, it takes repeated "bites," with this stellar snacking called a repeating partial tidal disruption event (rpTDE).

Each incident causes a flare of light from the vicinity of the black hole, as would be expected from the brightening seen during a standard TDE. But a strange pattern has emerged in rpTDES; each successive flare can become dimmer. Scientists have struggled to explain this dimming for some time, but finally a team of researchers from Syracuse University may have solved this puzzle.

To reach an answer to black hole flare dimming, the team considered a factor that hadn't been thought of before: the spin of the star itself. This element explained the dimming of black hole flaring and also helped to explain why not all rpTDEs play out the same.

"We were puzzled by this for two years," team leader Ananya Bandopadhyay of Syracuse University said in a statement.

A new spin on stellar snacking

Bandopadhyay and colleagues previously determined that how much material a star loses during repeated rpTDE episodes depends partially on its internal structure, which in turn depends on its mass.

Bandopadhyay compares a low-mass star to a fluffy meringue, which makes it more susceptible to the tidal forces generated by the black hole, allowing more material to be stripped from deeper within the star.

In contrast, a high-mass star has a structure more like an onion. That means that when such a stellar body buzzes a black hole in a rpTDE, its outer layers are stripped, but its core resists the influence of the black hole. Thus, as that outer layer is whittled away, there is less and less material to be stripped away in subsequent episodes.

However, that alone can't fully account for the dimming of flares from four of the ten currently discovered rpTDEs, because of the influence the black hole has on the star as it passes.

The team's prior work had identified that during rpTDEs, supermassive black holes exert a torque on the passing star that causes the star to spin faster during each passage.

That means even though less material falls to the black hole during each passage, the star returns over shorter and shorter periods of time. That helps keep flaring consistently bright. Thus, a recipe for dimming requires a new ingredient.

Bandopadhyay determined that this element could be a star that was already spinning rapidly before its first encounter with a supermassive black hole.

If a star is already rapidly spinning when it first encounters a black hole, the torque experienced doesn't increase that spin much. And without that increase in spin, there is no shortening of periods between episodes, meaning less and less material being stripped would result in dimming.

Of course, that leaves another question: why would a star be spinning so rapidly in the first place?

Rogue stars could be the answer

The key to this mystery could lie in the fact that most stars don't orbit the centers of their galaxies where supermassive black holes dwell alone, instead existing in binary partnerships.

"It is also extremely difficult to 'bind' a star to a supermassive black hole so tightly that it orbits the black hole in a matter of months, and yet they seem to do so in rpTDEs," team member Eric Coughlin of Syracuse University said.

The loss of a partner star, could cause a stellar body to be tightly bound to a supermassive black hole, completing an orbit once every few months.

During a process called Hills capture, as a stellar binary orbits a supermassive black hole and the gravitational influence of the black hole rips the binary apart, ejecting one star while capturing the other.

If this stellar binary was particularly tight, with the stars closely orbiting each other, this ejection and capture process could leave the trapped star rapidly spinning on a tight orbit.

"This work demonstrates that each of these peculiarities can be explained by the same underlying phenomenon: the tidal destruction of a binary system and the capture of one of the stars," Coughlin said. "From a theoretical standpoint, this is a major step forward in our understanding of the physics at play in these systems."

The discovery may have implications closer to home too. Though the supermassive black hole of the Milky Way, Sagittarius A* (Sgr A*), isn't currently involved in a rpTDE, it is orbited by many rapid stars. These findings may explain how they came to be there.

The team's research was published on August 18 in The Astrophysical Journal.

Astronomers have discovered a hitherto unseen population of so-called "radio galaxies" with fading "radio lobes." The discovery reveals what happens when the supermassive black hole engines that power these vast, blooming outflows of plasma stall. This discovery increases our understanding of the life cycles of galaxies.

The team behind this research studied 14 candidates for faded or remnant radio galaxies found in a region of the sky over Earth, studied intensely by the XMM-Newton X-ray spacecraft, called the XMM–Newton Large-Scale Structure (XMM–LSS) field.

Radio galaxies are extremely bright in radio waves and feature vast lobes of gas that can stretch out for millions of light-years. Remnant radio galaxies represent the final stage in the evolution of radio galaxies, at which point the jets from the galaxies' central regions, or active galactic nuclei (AGNs) powered by feeding supermassive black holes, have switched off. Therefore, these jets can no longer replenish the vast radio lobes, causing them to gradually fade.

The researchers studied the XMM–LSS field using the MeerKAT radio telescope, an array of 64 antennas located in the desert-like region of the Northern Cape, South Africa, the Jansky Very Large Array, and the LOFAR (Low-Frequency Array) network.

This powerful combination of observations allowed them to study how radio emissions from the lobes of radio galaxies change as the particles within them "age" and lose energy.

This allowed the researchers to determine that 12 of the 14 candidates actually are remnant radio galaxies, while the other two remain active radio galaxies.

The team also discovered something striking about the 12 confirmed radio galaxy remnants.

One thing that really stood out in this study was the ages of these remnants, which appeared to have been fading for between 8 million and 42 million years, with the average "fade age" being 12 million years.

This age is younger than the ages measured for radio galaxy remnants, which could indicate that astronomers have been missing a population of short-lived remnants.

This wasn't the only extraordinary finding in this study. The scientists also found that the remnants they looked at exist in a wide range of evolutionary stages, with some having jets that have only just switched off, while others are more evolved, having "powered down" long ago.

The new findings represent a major step forward in understanding the life cycles of radio galaxies, and also how supermassive black holes function as the engines powering jets that drive vast radio lobes.

The team's research was published on July 14 in the Monthly Notices of the Royal Astronomical Society.

A mysterious hum of gravitational waves that fills the cosmos may be the echo of "dark stars" that served as the seeds of the first supermassive black holes.

These low-frequency gravitational waves were detected back in 2023 using an array of cosmic lighthouses, or pulsars, in a so-called "pulsar timing array." Pulsars are neutron stars that spin rapidly and regularly while blasting out collimated beams of radiation from their poles that can be used to detect tiny fluctuations in space and time. Such fluctuations are caused by the gravitational waves, or ripples in spacetime.

For a long time, the source of this particular low-frequency gravitational wave background has been somewhat shrouded in mystery, but scientists have hoped that they may be encoded with the secrets of the universe as it was around 13 billion years ago. Indeed, the team behind this research believes this hum of spacetime ripples could help explain how supermassive black holes grew so rapidly before the universe was even a billion years old. They link this solution to hypothetical supermassive "dark stars" that may have collapsed and died in the early universe to birth massive black hole seeds, giving supermassive black hole growth a head start.

"Dark stars were originally proposed as objects that might be seen directly at cosmic dawn," Ilie said. "This work points to a completely different way of testing their possible role in cosmic history," team member Cosmin Ilie of Colgate University said in a statement. "Their descendants could leave a gravitational-wave imprint that persists all the way to the present-day universe."

Cosmic clocks and collapsing Dark Stars

Pulsar timing arrays detect gravitational waves when their passage squashes and stretches space as the waves ripple past them, causing tiny delays in the pulsars' beams of radiation reaching Earth.

Detecting a gravitational wave background, however, required monitoring pulsar timing arrays for many years.

"Pulsar timing arrays are usually thought of as probes of supermassive black-hole binaries in the relatively recent universe," Ilie said. "What our work shows is that the signal may also contain information about how the ancestors of those black holes formed at cosmic dawn.

"In that sense, gravitational waves observed today could provide a new window onto the birth of the first supermassive black holes."

The currently favored explanation for this background is a cosmic history of binary black holes spiraling together before merging, particularly pairings with combined masses of over 1 billion times the mass of the sun.

However, that doesn't explain where these supermassive black holes came from and how the James Webb Space Telescope (JWST) is routinely detecting them before the universe was even 1 billion years old — despite the fact that the feeding and merger chains proposed to create supermassive black holes should take over 1 billion years.

Ilie and his Colgate University colleague Sohan Ghodla questioned if supermassive balck hole growth began with heavy seeds, and if these heavy seeds were created by the collapse of dark stars.

Dark stars are hypothetical primordial stars that, rather than producing energy through nuclear fusion, are instead powered by self-annihilating dark matter within their cores. As dark matter fuels these primordial stars, they would remain cool compared to other stellar bodies, allowing them to continue to accrete matter throughout their lives.

This process would continue until Dark Stars reached masses millions of times that of the sun and collapsed under their own gravity, creating massive black holes; seeds that collide and merge to form supermassive black holes.

Ilie and Ghodla modeled the environment in which the resultant black hole seeds would exist and merge, calculating merger rates and the influence on the gravitational wave background.

They found supermassive dark star remnants could indeed provide a major, perhaps dominant, contribution to the gravitational wave background detected in 2023. That means the measurements provided by pulsar timing arrays could help determine how abundant heavy black hole seeds were in the early universe.

"Produce too many of these massive seeds, and you end up over-producing the pulsar timing array-detected signal," Ghodla said. "Produce too few, and you need other sources to efficiently assemble these supermassive black holes later in the life of the universe to match pulsar timing array observations."

The key determining factor here would be the masses of the dark matter haloes in which the dark stars live and in which the heavy black hole seeds form.

Determining if the researchers' theory is correct may have to wait for improvements in pulsar timing array measurements of the gravitational wave background, along with a better understanding of populations of black holes and their characteristics in the early universe.

The team's research was published on Monday (August 17) in the journal Physical Review D.

Astronomers have discovered that a jet of plasma erupting from a distant supermassive black hole at near-light-speed is being gravitationally lensed by an unseen clump of dark matter. The discovery could tell us about the source of cosmic "ghost" particles called neutrinos.

The supermassive black hole in question is powering a type of quasar called a blazar. All quasars involve supermassive black holes surrounded by vast quantities of material upon which the black holes feed. Material that isn't consumed by these feasting cosmic titans is channeled to the poles of the black holes, from where it is blasted out as plasma jets. A blazar differs from quasars in general because the jets it blasts out are directed at Earth. Blazars, like the one central to this study, designated PKS 2233-148, have long been proposed to be the cosmic particle accelerators that blast out neutrinos.

Neutrinos get their ghostly nickname because they carry no charge and very little mass, meaning that 100 trillion of them can pass through your body every second without you noticing a thing. This makes them hard to both detect and trace back to a source. This gravitationally lensed blazar could assist in that hunt, finally proving blazars are filling the universe with cosmic ghosts.

"These large-scale jets are cosmic accelerators and might be generating neutrinos," Silke Britzen at the Max Planck Institute for Radio Astronomy in Germany told Phys.org. "We study them to search for any peculiarities which might help us to gain a better understanding of neutrino emission."

Blazar jet receives a cosmic course correction

Astronomers have long been interested in PKS 2233-148, identifying this blazar as one that could solidify the link between neutrinos and the jets of feeding supermassive black holes. That is because one of its polar jets is aligned along our line of sight from Earth.

Britzen and colleagues took a new look at observations of PKS 2233-148 made by the Very Long Baseline Array (VLBA) on Earth, the Fermi space telescope, which viewed the blazar in gamma rays, and the X-ray instrument aboard the Swift space observatory.

This revealed how the motion of the jet of PKS 2233-148 changed over time, uncovering hitherto hidden details, including the fact that this blazar jet had been suddenly shifted from its expected path.

"We are very happy to have discovered as-yet-undetected phenomena in the jet, as well as in the gamma-ray light curve," Britzen said.

What could have caused this cosmic course correction? A phenomenon first predicted by Albert Einstein back in 1915 and an unseen cluster of the universe's strangest stuff, dark matter.

What is gravitational lensing and how can dark matter cause it?

The concept of gravitational lensing emerged from Einstein's theory of gravity, general relativity. General relativity states that objects with matter warp the very fabric of space, much like a bowling ball placed on a stretched rubber sheet. Gravity arises from that curvature.

And just as a cannonball would dent that hypothetical rubber sheet more than a bowling ball, an object with greater mass would cause a more extreme warp in space; its gravitational influence is greater.

Something cool happens when light passes this warped space; its usually straight path is curved. This means that when light from a background source passes a massive foreground object acting as a gravitational lens, it arrives at our telescopes at different times, meaning that the background source is magnified or, in extreme cases, can appear in multiple places in the same image.

In this case, it is the jet of PKS 2233-148 that is being lensed. But there is no object of great mass, like a galaxy or galaxy cluster, that can be seen in the right position to be doing the lensing. That leaves the possibility that the lensing body is something that can't be seen at all. Dark matter fits the bill.

Dark matter is effectively invisible because it doesn't directly interact with electromagnetic radiation, or light. In other words, dark matter doesn't emit light, and light doesn't bounce off it. That means even a clump large enough to play the role of a gravitational lens would be undetectable. But that doesn't mean light can't respond to the curvature of space caused by dark matter, just as it does to curvature caused by any body composed of "ordinary" matter like a star or a galaxy.

Like any gravitational lensing set-up, the lensing of the jet of PKS 2233-148 caused by this clump of dark matter requires precise alignment, and that means it is only a temporary thing.

"Because these are short-term phenomena, they are hard to find," Britzen said. "This is the first time that we find a lensing phenomenon which might hint at dark matter substructure."

Britzen and colleagues now hope to find other similar lensing events to further solidify the connection between blazars and neutrino factories.

The team's research was published on July 31 in the journal Monthly Notices of the Royal Astronomical Society.

A trio of heavyweight black holes are entangled in a dance of death that will quite possibly see them gradually all merge to form an even greater behemoth.

Scientists have discovered the black holes in a galaxy that is so far away its light has taken 12.5 billion years to reach us, meaning we see it as it was less than 1.3 billion years after the Big Bang. And it's offering strong supporting evidence that one of the ways black holes grew so massive so quickly in the early universe was through mergers.

"This is the first evidence of three active black holes in a single galaxy in the distant universe," Hannah Übler, an astronomer at the Max Planck Institute for Extraterrestrial Physics in Germany who led the study, said in a statement. "It suggests that processes in the early universe were efficient at bringing massive black holes together, setting the stage for the massive black-hole mergers we expect to detect with future gravitational-wave observatories."

The galaxy that plays host to the black holes is catalogued as J0148-4214 and is so far away (their redshift is 5.0167) that the James Webb Space Telescope (JWST), which made the discovery, could not see the black holes directly. Instead, the Integrated Field Spectroscopy unit on the JWST's Near Infrared Spectrometer (NIRSpec) measured the motion of hydrogen gas swirling around at high velocity in the accretion disks encircling each black hole.

"The JWST data allowed us not only to identify the three black holes, but also to estimate their masses, accretion rates and the stellar mass of the galaxy," Giovanni Mazzolari of the Max Planck Institute for Extraterrestrial Physics said in the statement. "We find a total stellar mass of about 1.3 billion suns, and the black holes represent a significant fraction of that."

Two of the black holes reside at the center of J0148-4214, separated by 620 light-years. One of these black holes has a huge mass of 80 million times the mass of our sun, while its companion is a relative pipsqueak at 600,000 solar masses. Yet despite its diminutive stature, the smaller black hole is growing at a tremendous rate by accreting gas faster than the Eddington limit. This is the theoretical maximum rate at which material can fall towards a black hole; if the rate is any higher then the accretion disk around the black hole becomes so dense and hot that radiation from the disk blows material back out again, stifling the black hole's feeding frenzy. This means the smaller black hole will only be able to keep growing at this rate for a short time before negative feedback calls a halt.

The third black hole is 5,500 light-years out from the center of J0148-4214 and has a mass two million times greater than the mass of our sun. This is about half the mass of the supermassive black hole at the center of our Milky Way galaxy, called Sagittarius A*. It's thought that this third black hole, and quite possibly the second one too, found their way into J0148-4214 via mergers between galaxies.

"These results are extremely exciting," said Roberto Maiolini of the University of Cambridge, who was a participant in the findings. "They suggest that black-hole merging may be an additional, fast route for their rapid growth in the early universe."

Mergers between black holes produce bursts of gravitational waves. Current gravitational-wave detectors — including The Laser Interferometer Gravitational-Wave Observatory (LIGO) in the United States, Virgo in Italy and KAGRA in Japan — are able to detect the high frequency, short wavelength gravitational waves from the mergers of stellar-mass black holes, the kind formed in certain supernova explosions. To detect the much longer wavelength, shorter frequency gravitational waves produced by the merger of supermassive black holes such as those in J0148-4214 requires a space-based detector with a baseline many millions of miles long.

To that end, the European Space Agency plans to launch LISA, the Laser Interferometer Space Antenna. If all goes to plan, by the mid-2030s. LISA will feature three spacecraft in triangular formation, each side of the triangle being 1.55 million miles (2.5 million kilometers) long. The three spacecraft will beam lasers at each other, looking for deviations in the travel time of those laser beams as evidence for the passing of a long-wavelength gravitational wave.

With regards to J0148-4214, however, there is a caveat: The third black hole might not be on a collision course with the other two. Instead, it could be heading out of the galaxy.

It's the classic three-body problem: How do three objects orbiting one another interact?

The two smaller black holes may have entered J0148-4214 as a binary pair. Then, as they were drawn closer to the 80-million-solar-mass black hole, the more massive black hole could have snatched the 600,000-solar-mass black hole while exchanging angular momentum with the two-million-solar-mass black hole to fling it away at high velocity. We see a similar effect in our galaxy with hypervelocity stars that are racing out of the Milky Way. These speedy stars used to be part of a binary pair of stars that got too close to Sagittarius A*, which is the black hole at the center of our galaxy. One half of the binary was captured by the black hole and the other was flung away.

Currently, there is no way to measure the direction of motion of the third black hole in J0148-4214 and confirm whether it will merge with the other two black holes or escape. If it did escape, it could still be wandering alone and dark in intergalactic space even now, 12.5 billion years later.

The findings are presented in the journal Astronomy & Astrophysics.

Supermassive black holes are best known for their immense gravity, pulling in everything that strays too close, even light. But new research suggests these cosmic giants can also hurl enormous amounts of energy outward, driving powerful disturbances that ripple hundreds of thousands of light-years through space.

A study led by Satoshi Yamada of Tohoku University in Japan found that winds generated by an actively feeding supermassive black hole are about 100 times more powerful than astronomers previously estimated.

These outflows, scientists say, inject an amount of energy comparable to several billion supernova explosions, driving turbulence through hot gas across distances of roughly 300,000 light-years —far beyond the boundaries of the host galaxy itself.

"Black holes are largely known for sucking matter in, but they also eject gas in the form of powerful winds," Yamada said in a statement. "These winds were thought to be contained within the galaxy, but our study revealed that the force is immensely more powerful than previously understood."

To measure the extent of those outflows, Yamada and his colleagues observed H1821+643, a bright quasar in the constellation Draco about 3.4 billion light-years from Earth. The galaxy hosting H1821+643 sits at the center of a dense galaxy cluster and harbors an active supermassive black hole estimated to be three to four billion times the mass of the sun.

During a weeklong observation in September 2024, Yamada and his team used XRISM, the X-ray satellite launched by Japan's space agency in 2023, to track the chemical signature of ionized iron atoms in the surrounding hot gas. By examining how the light from these iron ions stretched and broadened, the researchers were able to determine how fast the gas was moving and how turbulent it had become, according to the statement.

The observations revealed that the turbulence is driven by energy released from the quasar, with its effects reaching distances of about 300,000 light-years from the black hole, the study notes.

The result builds on years of observations of H1821+643, which is, in fact, the closest known quasar to Earth located within a galaxy cluster, according to NASA.

One of the more intriguing discoveries came in 2022, when observations of the black hole's spin using NASA's Chandra X-ray Observatory showed it rotates half as quickly as its smaller peers, which spin close to the speed of light.

"The million-dollar question is, why?" Christopher Reynolds, an astronomer at the University of Cambridge and co-author of the 2022 study, said in a statement at the time.

According to that study, one leading hypothesis is that giants like H1821+643 grew primarily through repeated mergers with other black holes arriving from different directions. Those chaotic collisions may have repeatedly disrupted the black hole's rotation instead of steadily spinning it up through a long-lived accretion disk.

While the exact origin of its sluggish spin remains an open question, the black hole's influence clearly extends far beyond its host galaxy.

"For the first time, we have shown that black holes influence the broader cosmic environment through a shock wave of astonishing power," Yamada said in the statement.

"Black holes are key drivers of gas flows and motion in space, transporting vast amounts of energy to different regions of the cosmos."

This research is also described in a paper published July 28 in the journal Nature Astronomy.

Astronomers have used the Very Large Telescope (VLT) to observe the violent outflow of material from a distant black hole. The observation once again shows that even the hungriest black holes are extremely messy eaters, while also revealing the "digestive processes" of these cosmic titans in unprecedented detail.

The research focuses on the black hole system Swift J1727.8−1613, located around 8,800 light-years away, and a violent bout of cosmic indigestion and the bright eruptions the system triggered back in 2023. That episode is what initially led to the discovery of Swift J1727.8−1613 in 2023, and it resulted in the system becoming one of the brightest X-ray sources in the sky over Earth.

A team of astronomers has now discovered that as this black hole greedily stripped a star of its stellar material, some of this matter was consumed, but other stellar material was blasted back into space as high-speed jets and powerful black hole winds. They also found that the most massive outflows of material happened when the black hole's feeding activity was much lower than previously thought. The upshot of this is the conclusion that black holes aren't quite the "bottomless pits" scientists had assumed, but are far more like complex cosmic digestive systems.

"People often imagine black holes simply swallowing everything around them," team leader Noel Castro Segura of the University of Warwick in the UK said in a statement. "What we're seeing is a much more complex process. Matter falls in, the system processes it, and a surprising amount is expelled again."

The changing face of a feeding black hole

Swift J1727.8−1613 consists of a black hole surrounded by a swirling platter of material pulled away from a companion star. This matter still has angular momentum, or rotation, so it can't directly fall to the black hole, but instead forms this structure, called an accretion disk.

The immense gravitational influence of the black hole generates intense tidal forces and friction in the accretion disk, superheating it and causing it to glow brightly.

The observations of this glowing disk conducted by Segura and colleagues differ from previous studies of black hole outbursts because their detailed study allowed them to watch the Swift J1727.8−1613 system change over time as it fed on a star.

The resulting "movie" of this feeding black hole revealed that as the cosmic titan blasted out jets, the accretion disk slowly feeding it underwent changes of its own.

That gives scientists a rare and fleeting insight into the connection that exists between matter falling to the maw of a black hole and the material being blasted out at near light-speed as jets of plasma.

The team also found that even after the feeding frenzy of this black hole had subsided, it seemed to still be powering black hole winds of dense gas. They suggest that the amount of material flung away by the black hole may eventually amount to the same mass as that consumed by the black hole, meaning half of its stellar meal was eventually lost to space.

"If black holes can continue shedding material even after their largest outbursts, it means they may be much less efficient eaters than we previously assumed," Segura added. "A significant fraction of the meal may never reach the black hole at all, changing our understanding of how binary stars in galaxies evolve."

The fact that this team was able to observe the entire feeding cycle of this black hole from its initial flare to its dramatic and rather windy end paints a clearer and more dynamic picture of this process than scientists have ever had access to before.

"We usually gravitate towards the dramatic fireworks when a black hole outburst begins, but our observations show that the finale can be just as intense," Kyle Solomons, Doctoral Researcher at the University of Cape Town, said.

The team's research was published on Wednesday (July 29) in the Monthly Notices of the Royal Astronomical Society (MNRAS).