Researchers have observed the strongest candidate yet for a "microblazar" — a dazzling object that has long been predicted to exist but never spotted.

Observations of microblazars would give astronomers closer views of black holes emitting powerful jets of energy and help them understand how these extreme objects behave.

Blazars are some of the most energetic objects in the universe. They are a type of quasar — a brightly glowing object fueled by a supermassive black hole stripping material from its host galaxy and then ejecting some of it in powerful, opposing jets of particles and radiation. To qualify as a blazar, one of those near-light-speed jets needs to point directly at Earth. Astronomers have previously discovered smaller versions of quasars, dubbed microquasars, and long theorized that there must be smaller versions of blazars as well.

Now, an international team led by astronomers in Spain, the Netherlands and Argentina has described a microblazar in a study accepted for publication in the journal Astronomy and Astrophysics.

"It is the first time that we have a serious candidate," Josep Martí, an astronomer at the University of Jaén in Spain and first author of the study, told Live Science.

The object, called IRAS 18293-0941, is located in our galaxy, about 12,000 light-years from Earth, and it's hidden behind a veil of dust. It is a binary system that includes a black hole that orbits a hot, gigantic star every 11 days. Matter from the star falls into the black hole, and some of this material is jettisoned into the surrounding environment in two opposing jets. One of those jets flares toward Earth.

These objects, as well as microquasars in general, are tricky to observe, Martí said. "Because of stellar evolution, you need to catch the system at the right time," he added. "The microquasar phase of evolution is very short, and so it is difficult to find one in that phase."

Theorists predicted that microblazars would have special characteristics that should help define them. These features include powerful emissions across the electromagnetic spectrum, rapid changes in brightness (variability), and a hotspot behind them where its opposing jet heats up the interstellar medium in the opposite direction of Earth.

To observe IRAS 18293-0941, the study authors used a variety of instruments ‪—‬ including the Calar Alto Astronomical Observatory in Spain, a network of radio astronomy telescopes called the European VLBI Network, and the MeerKAT radio telescope array in South Africa ‪—‬ as well as archival data from the Very Large Array in New Mexico.

They found that IRAS 18293-0941 has all of the expected microblazar characteristics, except one ‪—‬ variability. Microblazars have rapid variability, which means their brightness changes a lot in a short period, because one of the jets is facing Earth and small changes in brightness are amplified by an effect called Doppler boosting.

Martí said IRAS 18293−0941's lack of rapid variability could be explained by the dense cloud of gas surrounding it, which could smooth out quick fluctuations in brightness.

The researchers are currently investigating whether the observed area behind the microblazar is in fact a hotspot, study co-author Pedro Luque-Escamilla, an astronomer at the University of Jaén, told Live Science.

Even with one of the expected features missing, this object is a promising candidate for the first known microblazar. "The claims and the results of the paper are sensible and there are no questionable hidden assumptions," Kinwah Wu, a theoretical astrophysicist at University College London who was not involved in the research, told Live Science in an email. "The source in this paper had shown signatures of interactions between the jets and the ambient material, which naturally leads to [particle] interaction."

Svetlana Jorstad, a senior research scientist at the Institute for Astrophysical Research at Boston University who was not involved in the research, told Live Science in an email that the new study was "very interesting, important and comprehensive."

Itumeleng Monageng, an astronomer at the University of Cape Town who was also not involved in the research, added that the team's observations "presents a previously overlooked mechanism for generating some of the highest energy emissions observed."

Microblazars "may power some of the universe's most energetic processes," Monageng told Live Science in an email.

Martí, J., Luque-Escamilla, P. L., Marcote, B., Abaroa, L., Aguasca-Cabot, A., Combi, J. A., Romero, G. E., Paredes, J. M., García, F., Fogantini, F., Saavedra, E. A., Del Ser, D., & Van Den Eijnden, J. (2026). A Galactic microblazar as a potential accelerator of ultra-high-energy particles. Astronomy and Astrophysics. https://doi.org/10.1051/0004-6361/202661105

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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.

Some of the brightest objects in the universe may also hold the key to understanding how galaxies evolve — especially when gravity transforms them into giant cosmic magnifying glasses.

Using artificial intelligence to search through data from the Dark Energy Spectroscopic Instrument (DESI), astronomers have identified seven promising candidates for quasars acting as gravitational lenses — natural cosmic magnifying glasses created when a massive object's gravity bends and magnifies light from a more distant object.

These unusual systems could help researchers better understand how actively growing supermassive black holes evolve, according to a statement from Ohio State University.

"Quasars are like the baby pictures of a supermassive black hole," Everett McArthur, lead author of the study and a graduate student in astronomy at The Ohio State University, said in the statement. "So exploring how we get from quasars to those black holes is really important."

Quasars are the intensely bright centers of galaxies powered by actively feeding supermassive black holes. Studying these objects can help researchers understand how black holes evolve into the enormous ones found throughout the modern universe. But as these black holes pull in gas and dust, they release so much energy that they can outshine their entire host galaxies, making those galaxies difficult to study.

Rare cases where a quasar acts as a gravitational lens offer a way around that problem, giving astronomers a unique opportunity to observe both the quasar and the distant galaxy whose light is magnified by its gravity.

However, finding these rare alignments can be exceptionally challenging. To uncover them, the research team began with a catalog of roughly 800,000 quasars identified by DESI and used a machine-learning model to search for subtle signatures of gravitational lensing.

Because so few quasars acting as gravitational lenses are known, researchers had little real-world data to train their AI model. Instead, they generated simulated examples of these cosmic alignments, allowing the algorithm to learn what to look for before searching the DESI catalog. The algorithm narrowed the search to about 200 candidates, which researchers then reviewed manually. That process resulted in seven new quasar lens candidates.

The discoveries roughly double the number of known systems found through similar survey searches, according to the statement.

While artificial intelligence played a key role in finding the candidates, the discoveries highlight the scientific potential hidden within the massive datasets produced by modern astronomy. DESI is mapping millions of galaxies and quasars, creating an enormous archive that would be nearly impossible to search by hand.

Follow-up observations will be needed to confirm the newly identified quasar lenses and study their properties in greater detail. If verified, they could offer astronomers a powerful new way to investigate how supermassive black holes shaped the galaxies around them while demonstrating how AI can uncover rare cosmic phenomena hidden within the enormous datasets produced by modern sky surveys.

Their findings were published July 22 in The Astrophysical Journal.

Using NASA's Chandra X-ray space telescope, astronomers have spotted the blisteringly hot exhaust fumes of one the earliest quasars, cosmic "breath" with temperatures as great as 36 million degrees Fahrenheit. This intensely bright titan is powered by a feeding supermassive black hole engine.

The Chandra X-ray telescope observed a relatively silent quasar that existed 2.1 billion years after the Big Bang. The cosmic "exhaust fumes" from this black hole engines extend out for around 100,000 light-years around a quasar at the heart of a still-forming galactic cluster, or "proto-cluster" called MQN01. These blisteringly hot gas structures will eventually become the atmospheres that envelope modern clusters of galaxies, known as the intracluster medium (ICM).

Thus, this research reveals for the first time the exact moment in cosmic history that these galactic atmospheres began to form and gather.

"The central scientific question is to understand how this hot phase forms: what are the physical conditions of the gas during its formation and what processes contribute to its heating," team member Sebastiano Cantalupo of the University of Milan-Bicocca said in a statement.

"[The data] show extraordinary properties of the gas that could provide us with the first insights into how this hot phase of the circumgalactic medium, which we now see as intracluster medium, formed."

Start your engines...

The team behind this research spotted this hot gas structure after 180 hours of X-ray observations conducted by Chandra. Until now, X-ray detections such as this have only been made for quasars that sit in active galactic nuclei (AGNs) at the heart of "radio-loud" galaxies.

The X-ray emissions from these radio galaxies come from jets of particles blasted out from around feeding supermassive black holes at near-light speeds.

But the quasar at the heart of MQN01 differs from these because it is radio-quiet. This means the X-rays detected by Chandra from this quasar are uncontaminated by plasma jets, so the observation is entirely the result of the cosmic "motorbreath" from the quasar.

"We are facing one of the most distant detections of extended thermal X-ray emission associated with the formation of hot gas in dense regions of the universe, which will likely evolve into the known local ICM," Cantalupo said.

"We believe we have identified a phase in its life in which cold gas falls towards the gravitational potential of this massive halo and is heated by gravitational shocks, reaching temperatures of about 20 million Kelvin [36 million degrees Fahrenheit (20 million degrees Celsius)].

"The densities and pressures we measured are high: one to two orders of magnitude higher than those of clusters in our local universe."

The observations of this radio-quiet galaxy were possible thanks to the application of a technique usually used to analyze Seyfert galaxies, which host feeding supermassive black holes in the local universe (the area of space found within 1 billion light-years of Earth). The challenge the team faced was isolating the faint light from the gas from the blinding glare of gas closer to the central black hole.

"We were initially extremely skeptical ourselves," team leader Andrea Travascio of the INAF said. "Given the exceptional nature of the data, we sifted through every alternative explanation: from artificial outflows to instrumental contamination or other unsuspected effects. But each alternative scenario encountered insurmountable theoretical limitations. The thermal explanation is the only one consistent with the physical data."

Travascio and the team are now analyzing archival datasets from hundreds of other quasars to discover if this heating phase is common to protoclusters or if MQN01 is a rarity.

"Considering how unique the result was and also taking into account Chandra's technical difficulties in the final phases of its mission, the satellite has once again demonstrated its extraordinary ability to produce scientifically relevant results even after decades of operation," Travascio said.

The team's research was published on Friday (July 24) in the journal Astronomy & Astrophysics.

Fixing a problem inside one of the world's most sophisticated scientific observatories might seem like the kind of challenge that demands a multimillion-dollar upgrade or revolutionary new technology.

But for scientists working on the Laser Interferometer Gravitational-Wave Observatory (LIGO), which listens for ripples in spacetime generated by cosmic collisions like merging black holes, the solution to a mild but persistent engineering challenge turns out to be as simple as an off-the-shelf camera.

By pairing commercially available thermal imaging cameras with computer models, a team led by Jonathan Richardson at the University of California, Riverside, has developed a technique that corrects tiny, heat-induced distortions in the observatory's mirrors — an elusive flaw that scientists say currently limits how far into deep space the facility can look.

"It doesn't require any new technology development, which is almost unheard of for solving a LIGO instrumentation problem," Richardson said in a statement.

Once incorporated into LIGO's upcoming upgrade, Richardson and his team estimate the fix would extend the observatory's reach by roughly 33 million light-years.

That gain might sound like a drop in the ocean against the unimaginably vast scale of the universe, but because space expands in three dimensions, pushing a detector's reach even slightly opens up an exponentially larger window of space. Being able to look further into the universe will allow astronomers to "hear" many more cosmic ripples, in turn increasing the potential for discovering the universe’s most violent collisions that lie beyond LIGO's reach today.

LIGO detects these cosmic ripples, known as gravitational waves, using twin L-shaped facilities in the U.S. — in the states of Washington and Louisiana. Inside each detector, a laser beam shoots down two 2.5-mile-long (4-kilometer-long) tunnels, bouncing off pristine mirrors at each end. When a gravitational wave passes through Earth, it subtly stretches one tunnel and squeezes the other. That microscopic shift alters the laser beams ever so slightly, producing a tiny flicker of light that alerts scientists to a distant cosmic event.

Because these cosmic signals are inconceivably small, preserving every single photon is crucial. To accomplish this, LIGO relies on mirrors polished to reflect 99.9999%t of the laser light that strikes them, ranking them among the purest optical components ever built.

Yet even these near-perfect mirrors have had one unavoidable flaw. The mirrors still absorb a tiny fraction of that intense laser light. That energy turns into heat, warping the mirror's surface by just a few nanometers, enough to distort the laser beam and reduce the observatory's overall sensitivity.

Physicists already knew they could counteract these distortions by applying targeted heat to the back of the mirrors. The difficult part was measuring the distortions accurately enough such that the correcting heat could be applied with exact precision.

The new technique uses infrared thermal images and existing computer models to reconstruct a map of distortions across the mirror's surface.

"You can think of it like taking an infrared picture of a car engine," Richardson said in the statement. "An engineer can look at the temperature pattern on the outside and infer what's happening inside the engine. We're doing the same thing with LIGO's mirrors."

And the technique isn't just a fix for LIGO. It is also expected to become part of the foundational design for Cosmic Explorer, a proposed next-generation U.S. gravitational-wave observatory targeted for the mid-2030s.

With 25-mile-long (40-km-long) arms — 10 times larger than LIGO's — Cosmic Explorer is already designed to detect gravitational wave events far beyond the reach of today's observatories. This new technique will only supercharge its ultimate reach.

"The goal for the next generation of gravitational-wave detectors is to achieve about 10 times the sensitivity of today's instruments," Richardson said in the statement. "One of the key obstacles to achieving that is reducing the fundamental quantum mechanical noise that limits the precision of the measurements."

The technique is described in a paper published July 16 in Classical and Quantum Gravity.

The launch of NASA's next super telescope, the Nancy Grace Roman Space Telescope (Roman), may mean there is nowhere left for violent black holes to hide.

In fact, these cosmic cannibals may not even be able to hide from Roman at "cosmic noon," a period of the universe's history that occurred around 11 billion to 12 billion years ago. The study of these gory stellar events so early in the history of the universe could help reveal how supermassive black holes grew so big, so rapidly.

Occurrences of black holes ripping apart stars are called tidal disruption events (TDEs), and they happen when an unfortunate star's orbit brings it too close to the immense gravitational influence of a supermassive black hole. This simultaneously squashes and squeezes the star in a process called "spaghettification," with plasma pasta wrapping around the black hole and being fed gradually to it.

Because supermassive black holes are wrapped in a one-way, light-trapping boundary called an event horizon, the only way to study them is when they are actively consuming surrounding matter. Such matter swirls around them in what are known as accretion disks.

However, lighter supermassive black holes aren't ravenous feeders, making them harder to investigate. That is, until a star gets too close and is shredded in an incredibly bright TDE that can outshine the combined light of every star in the supermassive black hole's host galaxy. TDEs are more common to supermassive black holes with masses of about 100,000 to 100 million suns, because supermassive black holes with masses over 1 billion solar masses tend to immediately swallow their stellar snacks.

Previous research has suggested TDEs wouldn't be common in the early universe, because the first supermassive black holes wouldn't even have a mass of 100,000 times that of the sun and thus wouldn't shred stars. However, a new study has reassessed the frequency of TDEs around 1 billion to 2 billion years after the Big Bang, finding they could be more common than previously estimated. Especially during the crowded conditions found during cosmic noon.

Set to launch on Aug. 30, 2026, scientists are hoping Roman's High-Latitude Time-Domain Survey, which will repeatedly revisit a region of the sky equivalent to 90 full moons, will be a powerful tool in the hunt for TDEs in the early universe and their subsequent study. This team estimated that Rubin will detect thousands to tens of thousands of TDEs each year, with 100s dating back to cosmic noon.

"The Roman Space Telescope is going to be transformative for transient science [transients are astronomical events that light up the sky then fade away]," research team leader Mitchell Karmen of the Johns Hopkins University said in a statement. "Thanks to Roman's high sensitivity, we can find multiple tidal disruption events out to greater distances and earlier cosmic times than ever before."

This means Roman is ideally poised to solve a puzzle that has developed since its predecessor, the James Webb Space Telescope (JWST), began beaming data back to Earth in July 2022.

How could early TDEs solve the puzzle of black hole growth

Supermassive black holes with masses equivalent to millions or even billions of suns are found at the hearts of all large galaxies. When they are seen in the relatively local universe, that isn't so problematic; they have had plenty of time to grow via mergers and feeding.

However, the JWST has been routinely spotting supermassive black holes prior to the universe being even 1 billion years old. That is troubling because these early black holes should have had to undergo at least 1 billion years of mergers and gluttonous feeding to reach supermassive status. Scientists have two prevailing theories as to how this growth may have happened.

The first suggests supermassive black holes grow from "light seeds," beginning with black holes with masses just a few hundred times that of the sun that are born from the death and collapse of massive stars.

Such black holes might weigh up to a few hundred times the mass of the sun. These black holes would then merge over time, as well as consume surrounding gas at an incredible rate that facilitates rapid growth. For this theory to be the right one, every young galaxy would have to harbor a massive black hole at its center.

The second theory suggests early supermassive black holes grew from "heavy seeds" created directly from the collapse of vast clouds of primordial gas and dust. This would allow rapid growth because black holes could begin the whole merger and feeding process before the first stars lived and died.

Should this be the correct pathway, however, the fact that collapse events would be rare would make massive black holes at the heart of cosmic noon galaxies less common.

Because TDEs are common to less massive supermassive black holes, counting their occurrence at cosmic noon could give an indication of the masses of black holes during that epoch — the key to determining between heavy seeds and light seeds.

"Tidal disruption events help us probe the population of light supermassive black holes, which can help us discriminate between these models," Karmen said.

"Just by counting the number of TDEs as a function of redshift [a measure of cosmic distance], you can put meaningful constraints on the population of million-solar-mass black holes. Roman will be transformative in that it can probe tidal disruption events out to greater distances, so you can look at how the rate of TDEs evolves over time," team member Suvi Gezari, an associate professor of astronomy at the University of Maryland, said. “Just like the JWST has transformed our understanding of distant, high-redshift [very distant] galaxies, Roman is poised to transform our understanding of high-redshift transients."

The team's research was published on July 14 in The Astrophysical Journal.

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.