Category: black holes

Thanks to the James Webb Space Telescope (JWST), astronomers have been given a glimpse of the mechanisms that supermassive black holes use to feed themselves. The observations could help scientists discover how supermassive black holes with masses millions, often even billions, of times that of the sun grew so fast so soon after the Big Bang.

While all large galaxies have supermassive black holes at their hearts, some are slumbering giants, consuming little surrounding gas and dust, while others are ravenously feeding and acting as the engines of bright central galactic regions called active galactic nuclei (AGN). These feeding black holes also blast matter from their poles in jets that can drive gas and dust — the raw material needed for star formation — out of their host galaxies, thus cutting off star birth and effectively "killing" these galaxies.

Plus, the powerful cosmic titans get really puzzling when astronomers using the JWST spot them before the universe was even 1 billion years old. That's because the mechanisms by which black holes devour matter to grow and then merge to create even more massive black holes should take at least 1 billion years to achieve supermassive status. This is even more confusing because theories also say the most ravenously feeding black holes (and thus the fastest growing) should also push the matter they use for this growth away, in effect putting themselves on a diet. So, with all this in mind, how did supermassive black holes grow so rapidly in the early universe?

One explanation suggests supermassive black holes push away gas, starving themselves as predicted, but also that this matter eventually cools and falls back to the black hole. That would allow for another period of feeding and thus growth.

This explanation further suggests that as this gas cools down, it forms "streamers," or filaments, of gas just a few hundred light-years wide but which stretch thousands of light-years long. These would fall back to the center of the galaxy and form a swirling disk around its incumbent black hole, once again feeding it and triggering a new period of growth. This would then restart the jets from the black hole, which would again cut off the cosmic titan's food supply, allowing the whole process to begin once more.

The process would in essence be a self-regulating cycle of feasting followed by fasting. However, the connection between these filaments and supermassive black holes has been elusive, meaning this mechanism has resisted confirmation.

"What JWST is revealing is that black holes may be the ultimate cosmic recyclers," team leader Julie Hlavacek-Larrondo of the Université de Montréal said in a statement. "They release enormous amounts of energy that heat their surroundings, yet that same gas can later cool into thin filaments that fall back inward and feed the black hole again. We are finally seeing this self-sustaining cycle in action."

A dieting supermassive black hole

To solve the mystery of feasting black holes, the JWST turned its attention to a relatively close AGN situated at the heart of the central galaxy of the Centaurus Cluster, NGC 4696, located just 145 million light-years from Earth.

The Hubble Space Telescope previously studied this galaxy, uncovering a strange, hook-shaped swirl of gas near the central supermassive black hole of NGC 4696.

The JWST followed up this discovery by producing a detailed map of gas flowing at the heart of the galaxy. This revealed the hook-shaped feature is around 800 light-years wide and is composed of gas moving at incredible speeds of around 1.3 million miles per hour (600 kilometers per second).

More excitingly, the swirl of gas appears to be connected to a vast filament of material falling in toward the central supermassive black hole.

The team tested the JWST observations against a computer simulation, finding gas in the infalling filament scenario would indeed take a shape similar to that seen in NGC 4696.

"JWST is now showing us the final link of this closed loop," team member Helen Russell of the School of Physics and Astronomy at the University of Nottingham in the U.K. said in the statement. "The vast filamentary network of gas flows ultimately funnels gas down to a disk that fuels the black hole."

The team's research was published on Wednesday (July 16) in the Astrophysical Journal Letters.

There may be an easier way to describe how black holes "leak" energy than the theory Stephen Hawking proposed — and the newly suggested process is similar to how we describe a boiling pot of water. This simple (well, relatively simple) description could be used to model black holes in many situations such as during their formation, mergers with other black holes, eventual evaporation and even explosive death.

In the 1970s, legendary theoretical physicist Stephen Hawking wrote a letter to the journal Nature entitled "Black hole explosions?" explaining how these objects may leak thermal radiation, evaporate and eventually implode at the end of their lives. This radiation eventually became known as Hawking radiation.

But in new research, scientists have suggested an alternative to Hawking radiation. It involves describing the increase in disorder, or entropy, of black holes. Boiling water, as an example, is also often described based on its increase in entropy. For black holes, this measure of entropy is connected to characteristics like spin and energy, which means it could be used to understand how these cosmic titans respond to different events.

"Hawking's laws of black hole mechanics provided a satisfying connection between extreme and ordinary physics and have been the paradigm for 50 years, but they have a serious limitation," team leader Abhay Ashtekar of the Eberly College of Science at Penn State University said in a statement. "They were formulated for black holes at equilibrium — or unchanging over time — but black holes are constantly changing; they form, merge, and eventually evaporate. We wanted to find a way to overcome this limitation and extend the laws to black holes that are out of equilibrium."

Black holes, Einstein and Hawking

To investigate the origins of black holes, one has to go back to history's most famous physicist (sorry Hawking, you're number two), Albert Einstein.

In 1915, Einstein revealed his theory of gravity, general relativity. One consequence of the equations underpinning that theory was the possibility of a singularity, a point at which the equations of general relativity go to infinity. This represents the heart of a black hole.

Another consequence of the general relativity equations is a region of space around this singularity at which gravity is so extreme that the escape velocity of the area increases to a value greater than the speed of light. That region is the light-trapping outer boundary of the black hole known as the event horizon, which prevents us from ever seeing the singularity at the heart of the black hole or receiving information from it. In fact, until Hawking's work in 1974, this is why it was proposed that nothing at all can escape a black hole.

"The laws of black hole mechanics came directly from Einstein's equations," team member Daniel E. Paraizo, a graduate student in physics at Penn State, said. "Because you cannot see into a black hole, it seemed that there could be an infinite number of ways to make a black hole, making their entropy infinite as well. They were also thought to only absorb energy and never radiate, so their temperature was zero."

However, the advent of Hawking radiation somewhat changed this paradigm. By suggesting that black holes actually radiate thermal energy, Hawking redefined them in such a way that suddenly the laws of thermodynamics could be applied to black holes.

"This changed the thinking about the thermodynamic properties of black holes from a sort of mathematical concept described by equations, to being more of a physical reality," Paraizo said. "This opened the door to finding analogies in black holes of entropy and temperature used in thermodynamics."

In Hawking's recipe for black holes, the area of the event horizon is proportional to its temperature and entropy, and is inversely proportional to its mass and its spin.

"There is a problem, though," team member Jonathan Shu, also from Penn State, said in the statement. "These analogies only really work for a black hole that is at equilibrium. In dynamic situations, event horizons can form and grow in what we call flat regions of space-time, where nothing is happening."

Shu added that a consequence of this is the properties of black holes cannot be determined just by the local physics of the black hole. Instead, determining the properties of black holes relies on the prediction of events that may or may not happen in the future.

"Therefore, the area of event horizons cannot be a measure of the physical entropy of dynamical black holes," Shu argues. "If we want to understand black holes that are growing, evaporating and merging, we need a viable alternative."

For the team, this meant replacing the event horizon of a black hole with something they call a "dynamical horizon," already used when scientists simulate black holes. Now, the first law of thermodynamics — which states the energy of a closed system cannot be created or destroyed but rather can only change forms — can be applied to black holes even when they are involved in dynamic acts. It also means black holes are subject to the second law of thermodynamics, which says the total entropy of an isolated system will always increase over time, during their birth, merger and death.

"This allows us to extend the first and second laws of thermodynamics to black holes that are not at equilibrium, thereby overcoming the limitations of the paradigm that has been used for over half a century," Ashtekar said. "We can apply these generalized laws to better understand evaporating black holes in quantum theory and black hole mergers."

The team's research was published in June in the journal Physical Review Letters.

The first of 10,000 missing black holes in the Omega Centauri globular cluster has been found thanks to teamwork by the Hubble and James Webb space telescopes.

The two observatories discovered the black hole after watching a star orbiting around something massive but dark, and which therefore could not be seen. The Hubble data ran from 2003 to 2023, and the James Webb Space Telescope picked up after that to help refine the measurements.

Astronomers used the space telescopes to focus on a particular star in a binary system that appeared to be home to another, dark object called oMEGACat BH-2. Previous studies had suggested that the dark object was a neutron star. However, the new results are conclusive: the object has a mass 4.46 times that of the sun. This is too massive to be a neutron star, so it must therefore be a black hole.

Omega Centauri is the most massive of our Milky Way galaxy's globular clusters. It is so massive that astronomers suspect that it is actually the core of a dwarf galaxy that has lost most of its stars to the Milky Way's gravitational cannibalism, which over the aeons has torn strips from Omega Centauri. Even so, Omega Centauri still contains about 10 million stars, collectively located 18,000 light-years from Earth.

In 2024, astronomers using the Hubble Space Telescope found clinching evidence that an intermediate-mass black hole – one that has a mass about 8,200 times that of our sun – lurks at the center of Omega Centauri, strengthening its claim of being the remnant of a dwarf galaxy, since galaxies harbor black holes at their center but star clusters typically do not.

However, alongside this intermediate-mass black hole should be about 10,000 other stellar-mass black holes born from the supernova explosions of massive stars. Searches have focused on binary systems where a star orbits a compact object, but until now astronomers had drawn a blank.

Now, a team led by Matthew Whitaker of the University of Utah in Salt Lake City have come along to save the day by diligently sifting through 20 years of Hubble observations, plus additional supporting views from the JWST, to uncover a stellar-mass black hole in Omega Centauri for the first time.

Whitaker's team used a technique called astrometry, which is the measurement of the changing positions of stars as they move through space. Although the black hole itself is dark, it is orbited by a normal star with a mass 78% that of our sun. Thanks to the unprecedented vision of Hubble and the JWST, Whitaker and his colleagues were able to track the motion of this star around the black hole.

It turns out that the star is on a 94-year-long orbit around the black hole, which is the widest separation of a binary composed of a stellar-mass black hole and star ever found. Over that 20-year-period, Hubble saw less than a quarter of the star's total orbit, but it coincided with the star's closest approach to the black hole, during which the star moved faster.

Based on this motion, Whitaker's team were able to measure the strength of the black hole's gravitational field acting on the star, and from that calculate the mass of the black hole.

"The precision of these measurements is incredible, down to a fraction of a pixel on Hubble and Webb's detectors," said Whitaker in a statement. "It would not have been possible to find this black hole without these two space telescopes."

Given how wide the orbit of the star is around the black hole, the likelihood is that the black hole's gravity captured the star when it passed close. This is a state of affairs that will not last forever; within another billion years, encounters with other stars in the crowded environs of the cluster will probably pluck the black hole's companion away.

The mass of oMEGACat BH-2 does seem unusual, however, in the sense that it is lower than expected. The mass of oMEGACat BH-2 exists in a void that has only become apparent during the past eleven years of gravitational wave detections. These gravitational waves are produced by the mergers of stellar-mass black holes, but black holes with masses between 2.5 times the mass of our sun (the theoretical limit for neutron stars) and five solar masses are conspicuous by their absence in the gravitational-wave events. Yet here is oMEGACat BH-2, sitting within that mass gap.

"It's important to understand black hole populations in globular clusters because there's uncertainty about their physics and formation," said Anil Seth of the University of Utah.

"More specifically, understanding the process of forming black holes and then dynamically forming binaries is vital, because it affects our ability to interpret and understand gravitational-wave events. Environments like Omega Centauri are the primary places where we think binaries are merging and creating these waves."

In particular, the stars of Omega Centauri are more primitive than our sun, chemically speaking, with fewer elements heavier than hydrogen and helium. Which types of massive stars produce black holes when they explode as supernovas is still an area of active research, but oMEGACat BH-2 adds another complication to the mix in that its progenitor star contained few heavy elements.

"We need to figure out how that happens," said Seth.

So that's one down, and 9,999 or thereabouts to go. Whitaker's team continue to use Hubble and JWST data to find more stellar-mass black holes in Omega Centauri, but he also highlights the potential of NASA's Nancy Grace Roman Space Telescope to find black-hole binary systems in our Milky Way galaxy at least when the telescope launches later this year.

"Roman … will image the crowded galactic bulge, including the galactic center, very regularly with Hubble-like resolution and with a much wider field of view," said Whitaker. "We're hoping we'll be able to find black hole binary systems like this one because of the regular cadence of Roman's observations."

The details regarding oMEGACat BH-2 are described in a paper published on July 13 in The Astrophysical Journal Letters.

A supermassive black hole at the heart of a nearby galaxy is behaving similarly to black holes that existed just after the Big Bang, voraciously feeding on copious amounts of matter. The relatively close cosmic titan could therefore provide insight into the much more distant universe.

Indeed, the intense accretion behavior demonstrated by the supermassive black hole, which sits at the center of the galaxy SDSS J110546.07+145202.4 located 1.8 billion light-years away, is something scientists have only ever seen in the earliest supermassive black holes.

SDSS J110546.07+145202.4 has been shining brightly in radio waves for many years, and these waves were the smoking gun that pointed to the feeding habits of the galaxy's central black hole.

"Such high-energy events can provide astronomers with a wealth of insights," Kovi Rose from the University of Sydney’s Sydney Institute for Astronomy said in the statement. "By observing these jets and outbursts, we can study the physical processes in some of the most extreme environments in the universe."

Even the hungriest black holes are messy eaters

All large galaxies have a supermassive black hole at their heart with masses of millions or even billions of times that of the sun. However, not all supermassive black holes accrete vast amounts of matter.

For example, the supermassive black hole at the heart of our galaxy, the Milky Way, Sagittarius A*, consumes so little gas and dust from its surroundings that, were it a human being, it would be existing on a diet of one grain of rice every million years. (That is one heck of a diet.)

When black holes are surrounded by copious amounts of gas and dust, their immense gravitational influence causes this material, in a flattened swirling cloud called an accretion disk, to glow brightly across the electromagnetic spectrum, from low-energy radio waves to high-energy X-rays.

Additionally, supermassive black holes are notoriously messy eaters, meaning some of the matter in accretion disks is channeled to the poles of the black hole, from where it is blasted out as jets of plasma traveling at speeds approaching the speed of light. These jets too are responsible for bright emissions of electromagnetic radiation.

Radio signals from the spiral galaxy SDSS J110546.07+145202.4 underwent a 20-fold increase in radio brightness over a short period, increasing to around 10 quadrillion times the intensity of the radio brightness of the sun. This happened around 8 years ago, and the galaxy has yet to show any sign of dimming.

"We are dealing with the prototype of a new class of galaxies that undergo rapid changes in radio emission," team member Phil Edwards from CSIRO, Australia’s national science agency, said.

Team leader Stefanie Komossa of the Max-Planck-Institute for Extraterrestrial Physics in Garching, Germany, added: "Luminous radio radiation from rapidly growing, lightweight black holes is rare to begin with. Their transition into a long-lasting, radio-bright state has never been observed before."

The source of this electromagnetic radiation is situated at the heart of SDSS J110546.07+145202.4, right by its central supermassive black hole. The team thinks the brightening of this galaxy began because the rate of matter falling into its supermassive black hole had increased, triggering the generation of plasma jets.

The increase in mass consumption of the supermassive black hole is leading to a level of growth that hasn't been seen in black holes outside of the early universe before. That means that SDSS J110546.07+145202.4 and its feasting supermassive black hole are set to be prime targets for astronomical investigations for some time to come, especially as proxies for ravenous black holes and rapidly growing early galaxies.

"With sensitive facilities like the incoming SKA telescopes, we'll be able to identify similar radio transients in future sky surveys," Komossa said. "This is crucial for filling the gaps in our understanding of the early universe."

The team's research was published in May in The Astrophysical Journal.

Using the European Space Agency's Euclid space telescope, astronomers have discovered a treasure trove of 31 black-hole-powered quasars in the early universe. The most impressive of these new discoveries is the most ancient and distant quasar ever seen, shining with the light of a trillion suns just 670 million years after the Big Bang.

Quasars occur when supermassive black holes with masses millions or even billions of times that of the sun are surrounded by swirling disks of matter called accretion disks. As accretion disks gradually feed these central cosmic titans, the immense gravity of the black holes generates intense friction, causing this matter to glow so brightly that their luminosity can exceed the combined light of every star in their host galaxies.

Despite this, quasars can still be difficult to spot at vast cosmic distances, with their light difficult to distinguish from the light of much more proximate stars. Thus, the hunt for the earliest quasars has been on for decades, with scientists hoping that the discovery of these bodies could help explain how supermassive black holes grew so rapidly so shortly after the Big Bang. Launched in 2023, Euclid has fulfilled its promise in its mission to discover early quasars, with this hitherto unprecedented haul of 31 of these black hole engines.

"These early quasars date back to the Universe's infancy," team leader Daming Yang of Leiden University in the Netherlands said in a statement. "By finding and studying them, we can better understand how these enormous systems formed and grew so quickly — one of the greatest mysteries in astrophysics."

Previously, astronomers took around a decade to discover the first ten or so quasars at distances like this, which makes it incredibly impressive that Euclid has managed to detect more than three times that many ancient black hole engines in just a single year of observations.

The tip of the iceberg

Thanks to this new treasure trove of quasars discovered when the 13.8 billion-year-old universe was merely 5% of its current age includes not just the brightest examples of these objects, but also some fainter quasars. That now means scientists can finally study these objects as a population.

"Euclid is a true game-changer," Yang continued. "Before, we could only find a handful of the very brightest ancient quasars, but Euclid lets us search far more efficiently across huge areas of sky to capture much fainter light. It’s a unique tool for quasar hunting."

Of the 31 new quasars, 12 existed when the universe was around 770 million years old, but the two that really stand out are the quasars designated EUCL J172902.75+641018.1 and EUCL J125308.55+705432.3, which are around 13 billion light-years away and existed just 670 million years after the Big Bang. That makes them the most ancient quasars ever documented.

"This finding more than doubles the number of quasars we know of that are so ancient," Antonio La Marca , a European Space Agency (ESA) Research Fellow on the Euclid team, said in the statement. "The Euclid team has taken a true 'census' of quasars at the dawn of the Universe for the first time. It's a big step towards understanding these fascinating objects on a more fundamental level."

The quasars date back to a period of the cosmos known as the epoch of reionization, which lasted from around 680 million years after the Big Bang to 1.1 billion years after the Big Bang. During this period, the universe's "dark ages" drew to a close with photons, particles of light, suddenly free to traverse the cosmos. Thus, these 31 quasars offer a unique opportunity to study this vital period in cosmic history.

"Ancient quasars are rare discoveries," ESA Euclid Project Scientist Valeria Pettorino said in the statement. "They're interesting in themselves, but also time machines that enable us to explore the early universe and understand how the first generation of galaxies came to be."

The 31 quasars were discovered as part of the Euclid Wide Survey, which will eventually cover around one-third of the total sky over Earth.

Scientists hope that this survey will shed light on the so-called "dark universe" comprised of two of the most pressing cosmic mysteries: dark energy, the puzzling force driving the acceleration of the expansion of the universe, and the nature of dark matter, the most abundant "stuff" in the cosmos which remains effectively invisible.

"Euclid's capabilities are unrivalled," Pettorino concluded. "The telescope combines a large area, depth, sharp imaging, and unique space-based infrared vision in a way that lets us pick out rare, extremely distant objects far more efficiently than before."

The team's research was published on Monday (July 6) in the journal Astronomy & Astrophysics.

Mysterious "little red dots" discovered in the early universe by the James Webb Space Telescope could harbor buried black holes that fire high-energy cosmic "ghost particles" through the cosmos.

Neutrinos are referred to as ghost particles because as chargeless and near-massless particles, hundreds of trillions of them stream through your body every second at nearly the speed of light. Plus, the source of high-energy neutrinos frequently detected on Earth is something of a mystery.

And another cosmic mystery is the existence of the "little red dots," which are galaxies that have been discovered by the James Webb Space Telescope (JWST). Though common around 600 million years after the Big Bang, these dots seem to disappear before the universe gets to 2 billion years old. Some researchers have theorized that these curious small galaxies could harbor black holes that are buried in thick shrouds of cosmic dust. If that is the case, then the dots could be a major contributor of high-energy neutrinos, linking these two mysteries.

Neutrinos are produced when other particles, such as protons, collide with particles of light, or photons, or with different sorts of matter. This usually occurs in gas-dense environments, but the ghost-like characteristics of neutrinos mean they have little trouble escaping into the universe at large.

Usually, the events that create high-energy neutrinos also give rise to high-energy photons called gamma-rays. However, neutrinos are so abundant as the second most common particles in the cosmos that if all sources of neutrinos also created gamma-rays, the gamma-ray background of our universe should be much greater than it actually is.

That means some sources of high-energy neutrinos must be located in environments from which gamma-rays can't readily escape — and that's where the little red dots enter the picture. These curious objects display very little emission associated with galactic jets or other outflows. This led this team to assume that the lack of these emissions, which should come in the form of X-rays and radio waves, is because the black holes and associated jets in Little Red Dots are buried in dense halos of dust and gas.

"In the scenario we considered, abundant photons and dense gas are expected to exist around the central black hole in a little red dot, which may allow such collisions to occur efficiently," team leader Riku Kuze of Kyoto University said in a statement.

Kuze and colleagues estimated the contribution that the little red dots could add to the universe's neutrino background. This revealed that, should particle acceleration be occurring in the buried black holes within the dots, these environments could produce high-energy neutrinos to contribute a significant fraction of the high-energy neutrino background observed on Earth. This would be while also suppressing gamma-ray escape.

"Although it is difficult to observe the individual objects directly, we believe this study is significant because it is the first to demonstrate that, given their abundance, these little red galaxies could account for a part of the observed high-energy neutrinos," said Kuze.

Neutrinos come in more than one type, or flavor; thus, the next step for the team will be to determine the ratio of neutrino flavors generated by buried black holes in the little red dots and to determine if this matches cosmic abundances witnessed.

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

The loudest crash of gravitational waves ever heard has offered us insight into event horizons, the boundaries beyond which nothing can escape the grips of black holes.

The gravitational wave signal GW250114 was picked up in January 2025 by LIGO (Laser Interferometer Gravitational-Wave Observatory), Virgo, and KAGRA ( Kamioka Gravitational Wave Detector). The signal was created when two black holes with around 32 times the mass of the sun collided and set the very fabric of space rippling.

Now, a team of researchers assessed this signal and found a feature in the gravitational waves represents the collective event horizon of the involved black holes at the very moment of that collision.

"We measured the last sound the black holes made when they crashed. Hidden within that signal is a small component, called direct waves, that had not previously been well understood," research co-leader Neil Lu, from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav), said in a statement. "Our new analysis allows us to decipher this component and extract unique information from close to the event horizon."

The team's research presents the intriguing possibility that scientists could use gravitational waves to study these mysterious black hole boundaries.

Event horizons and the point of no return

The concept of an event horizon first emerged through solutions to the equations of Albert Einstein's 1915 theory of gravity, general relativity. These solutions were developed by Karl Schwarzschild while serving with the German army on the Eastern Front in the First World War.

Schwarzschild found a point around a body with mass at which the escape velocity, the speed needed to escape the gravitational grip of that body, exceeds the speed of light. Also known as the Schwarzschild radius, the size of that boundary depends on the mass of the body. So the Schwarzschild radius for the sun would be about 1.86 miles (3 kilometers) from its center of mass; for the Earth, it would be just 0.35 inches (9 millimeters) from our planet's center of mass. That's the case with all planets and stars; the Schwarzschild radius is well within the bodies of those objects.

However, for a black hole, the Schwarzschild radius is far from the center of mass, acting as a light-trapping outer boundary: the event horizon. To escape the gravitational grip of a black hole from this point, matter would have to accelerate to a speed faster than the speed of light, which Einstein's theory of special relativity tells us would require infinite energy. Nothing in the universe travels faster than light; thus, nothing escapes the event horizon.

To understand why that shrouds a black hole in mystery, consider how no signal can travel faster than light. That means the event horizon is a one-way barrier for information. A black hole can swallow it, but the event horizon prevents it from spitting information out. We can never observe the interior of a black hole.

It's little wonder scientists are so keen to study event horizons and what happens there. They don't only want to understand the physics of matter engaged on a one-way trip into the maw of a black hole, but the effect on the very fabric of space itself these cosmic titans have.

The immense gravitational influence of black holes means that, as they spin, they drag the very fabric of space along with them, a phenomenon called "frame-dragging" or the Lense-Thirring effect. This introduces another rule about event horizons — not only does nothing escape this boundary, nothing there sits still either. This research brings scientists one step closer to understanding those rules in greater detail than ever before.

"We studied GW250114, the loudest binary black hole signal observed to date, about three times louder than the first gravitational-wave signal detected a decade ago," team co-leader Ling Sun of OzGrav said. "Our analysis shows that this exceptionally loud signal can be used as a powerful probe of the remnant black hole's horizon, allowing us to measure its two fundamental properties: rotation frequency and surface gravity."

The results could also shed more light on the behavior of gravity in the most extreme environment in the universe, at the very edge of a black hole.

"These measurements mark a first step towards future tests of general relativity with direct waves," Lu said.

The research was published on Wednesday (June 24) in the journal Nature.