Astronomy

How does a Super-Massive Black Hole 'flare'?

How does a Super-Massive Black Hole 'flare'?


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This week we have read of evidence of the Super Massive Black Hole in the centre of the Galaxy 'flaring'.

My understanding is that light cannot escape from a black hole.

My question is: How does a Super-Massive Black Hole 'flare'?


The flare happens just outside the black hole. Matter which aproaches a black hole but not perfectly straight on doesn't fall into it immediately. It gets pulled around the black hole, just as a satellite is pulled around the Earth.

If the object is a single small particle, that's almost the end of the story. Gravitational radiation and the precise effects of GR will cause its orbit to decay until it eventually falls in, but if it's small enough not much of anything is emitted in the process.

If there are lots of objects in the neighbourhood, or if your obect is something relatively large and diffuse (like a gas cloud, or a planet or star) on the other hand, different things happen. As gravity pulls on different parts of it with different strengths (tides) the object gets stretched and then pulled to pieces, and multiple objects collide and interact in all sorts of ways. Magnetic fields also start to play a role. Some of that matter escapes completely, but much of it ends up in a disk (a little like Saturn's rings, but less well organised) around the hole. By this point all the stretching and collisions have made it very hot, so it shines.

Now even within the disk there are collisions and friction, and they have the overall effect of heating the matter in the disk and pushing some of it out of orbit, so that it falls into the hole, getting even hotter in the process.

So finally we come to a flare. There are probably many kinds of flare-up in this basically unstable setup, but the most obvious is when a particularly large object or cloud of gas falls into the accretion disk, or when some instability in the disk causes a large amount of matter to fall out of the disk. Either way, the larger amount of hotter matter shines more, and we see a flare.


A supermassive black hole usually has an accretion disc composed of gas, dust and other debris attracted into close orbit. These materials gradually fall toward the black hole, becoming heated by compression and friction as they go. When a large mass of this matter is drawn to the inner edge of the accretion disc just before it disappears for ever into the black hole, the result is a flare up or rapid but temporary brightening of the accretion disc. The light doesn't escape from the black hole itself, but from regions just outside the black hole. There are also high energy particle jets accelerated by the black hole's magnetic field in precisely opposite directions by the black hole's magnetic poles, but again they are emitted before they enter the event horizon, not afterwards.


Indian Astronomers Detect Huge Optical Flare From Super Massive Black Hole

New Delhi: Indian astronomers have reported one of the strongest flares from a feeding super massive black hole or blazar called BL Lacertae, analysis of which can help trace the mass of the black hole and the source of this emission, the Department of Science and Technology said on Saturday. Also Read - Most Detailed, New 3D Map of Milky Way Galaxy Ever Made Revealed Shows Earth Heading Towards Black Hole

Such analysis can provide a lead to probe mysteries and trace events at different stages of evolution of the Universe, it said. Also Read - Black Holes Don't Suck in Objects Like Vacuum Cleaner: Expert Busts Popular Myth

Blazars or feeding super massive black holes in the heart of distant galaxies receive a lot of attention from the astronomical community because of their complicated emission mechanism. They emit jets of charged particles travelling nearly at the speed of light and are one of the most luminous and energetic objects in the Universe. Also Read - Nobel Prize in Physics Jointly Awarded to Roger Penrose, Reinhard Genzel & Andrea Ghez For Black Hole Research

&ldquoBL Lacertae blazar is 10 million light-years away and is among the 50 most prominent blazars that can be observed with the help of a relatively small telescope. It was among the 3 to 4 blazars that was predicted to be experiencing flares by the Whole Earth Blazar Telescope (WEBT), an international consortium of astronomers,&rdquo the statement said.

A team of astronomers led by Alok Chandra Gupta from Aryabhatta Research Institute of Observational Sciences (ARIES), an institute of the Department of Science & Technology, who has been following the blazar since October 2020 as part of an international observational campaign detected the exceptionally high flare on January 16 with the help of Sampurnanand Telescope (ST) and 1.3m Devasthal Fast Optical Telescopes located in Nainital.

The data collected from the flare observed will help calculation of the black hole mass, size of emission region, and mechanism of the emission from one of the oldest astronomical objects known, hence opening a door to the origin and evolution of the Universe, it added.


Black Hole Has Major Flare

The baffling and strange behaviors of black holes have become somewhat less mysterious, with new observations from two NASA missions.

The baffling and strange behaviors of black holes have become somewhat less mysterious recently, with new observations from NASA's Explorer missions Swift and the Nuclear Spectroscopic Telescope Array, or NuSTAR. The two space telescopes caught a supermassive black hole in the midst of a giant eruption of X-ray light, helping astronomers address an ongoing puzzle: How do supermassive black holes flare?

The results suggest that supermassive black holes send out beams of X-rays when their surrounding coronas -- sources of extremely energetic particles -- shoot, or launch, away from the black holes.

"This is the first time we have been able to link the launching of the corona to a flare," said Dan Wilkins of Saint Mary's University in Halifax, Canada, lead author of a new paper on the results appearing in the Monthly Notices of the Royal Astronomical Society. "This will help us understand how supermassive black holes power some of the brightest objects in the universe."

Supermassive black holes don't give off any light themselves, but they are often encircled by disks of hot, glowing material. The gravity of a black hole pulls swirling gas into it, heating this material and causing it to shine with different types of light. Another source of radiation near a black hole is the corona. Coronas are made up of highly energetic particles that generate X-ray light, but details about their appearance, and how they form, are unclear.

Astronomers think coronas have one of two likely configurations. The "lamppost" model says they are compact sources of light, similar to light bulbs, that sit above and below the black hole, along its rotation axis. The other model proposes that the coronas are spread out more diffusely, either as a larger cloud around the black hole, or as a "sandwich" that envelops the surrounding disk of material like slices of bread. In fact, it's possible that coronas switch between both the lamppost and sandwich configurations.

The new data support the "lamppost" model -- and demonstrate, in the finest detail yet, how the light-bulb-like coronas move. The observations began when Swift, which monitors the sky for cosmic outbursts of X-rays and gamma rays, caught a large flare coming from the supermassive black hole called Markarian 335, or Mrk 335, located 324 million light-years away in the direction of the constellation Pegasus. This supermassive black hole, which sits at the center of a galaxy, was once one of the brightest X-ray sources in the sky.

"Something very strange happened in 2007, when Mrk 335 faded by a factor of 30. What we have found is that it continues to erupt in flares but has not reached the brightness levels and stability seen before," said Luigi Gallo, the principal investigator for the project at Saint Mary's University. Another co-author, Dirk Grupe of Morehead State University in Kentucky, has been using Swift to regularly monitor the black hole since 2007.

In September 2014, Swift caught Mrk 335 in a huge flare. Once Gallo found out, he sent a request to the NuSTAR team to quickly follow up on the object as part of a "target of opportunity" program, where the observatory's previously planned observing schedule is interrupted for important events. Eight days later, NuSTAR set its X-ray eyes on the target, witnessing the final half of the flare event.

After careful scrutiny of the data, the astronomers realized they were seeing the ejection, and eventual collapse, of the black hole's corona.

"The corona gathered inward at first and then launched upwards like a jet," said Wilkins. "We still don't know how jets in black holes form, but it's an exciting possibility that this black hole's corona was beginning to form the base of a jet before it collapsed."

How could the researchers tell the corona moved? The corona gives off X-ray light that has a slightly different spectrum -- X-ray "colors" -- than the light coming from the disk around the black hole. By analyzing a spectrum of X-ray light from Mrk 335 across a range of wavelengths observed by both Swift and NuSTAR, the researchers could tell that the corona X-ray light had brightened -- and that this brightening was due to the motion of the corona.

Coronas can move very fast. The corona associated with Mrk 335, according to the scientists, was traveling at about 20 percent the speed of light. When this happens, and the corona launches in our direction, its light is brightened in an effect called relativistic Doppler boosting.

Putting this all together, the results show that the X-ray flare from this black hole was caused by the ejected corona.

"The nature of the energetic source of X-rays we call the corona is mysterious, but now with the ability to see dramatic changes like this we are getting clues about its size and structure," said Fiona Harrison, the principal investigator of NuSTAR at the California Institute of Technology in Pasadena, who was not affiliated with the study.

Many other black hole brainteasers remain. For example, astronomers want to understand what causes the ejection of the corona in the first place.

NuSTAR is a Small Explorer mission led by Caltech and managed by NASA's Jet Propulsion Laboratory in Pasadena, California, for NASA's Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp., Dulles, Virginia. NuSTAR's mission operations center is at UC Berkeley, and the official data archive is at NASA's High Energy Astrophysics Science Archive Research Center. ASI provides the mission's ground station and a mirror archive. JPL is managed by Caltech for NASA.


Shedding Sources

Reconstruction of the orbits of several S stars at the center of the galaxy. The two colored orbits mark two stars with the closest known approaches to Sgr A*.
Keck / UCLA Galactic Center Group

Sgr A*’s flares likely came from an abrupt increase in the amount of material available to accrete onto this black hole. Murchikova identifies two likely sources of this excess material.

  1. Shedding S stars
    The dense nucleus of our galaxy hosts a population of stars on tight orbits around Sgr A*. These stars shed mass via stellar winds, and when the stars swing close around Sgr A* at the pericenter of their orbit, this shed mass could accrete onto Sgr A*.
  2. Disintegrating G objects
    Also known to orbit close to Sgr A* are so-called G objects. These extended sources may be gas clouds, stars, or a combination of the two — we’re not sure yet! Tenuous G objects lose mass as a result of friction as they orbit, exhibiting higher rates of mass loss as they get closer to Sgr A* and are stretched out into shapes with large surfaces areas passing through dense background material. The mass they lose through this disintegration at pericenter could then accrete onto Sgr A*.

Astronomers Find Clue to How Supermassive Black Holes Emit X-ray Flares

In 2014, NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) and the agency’s Swift satellite observed an X-flare from the supermassive black hole in Markarian 335, a galaxy located 324 million light-years away in the constellation Pegasus. The observations allowed astronomers to link a shifting corona to an X-ray flare for the first time.

A supermassive black hole is depicted in this artist’s concept, surrounded by a swirling disk of material falling onto it. Image credit: NASA / JPL-Caltech.

According to the astronomers, led by Dr Dan Wilkins of Saint Mary’s University in Canada, supermassive black holes send out beams of X-rays when their surrounding coronas shoot, or launch, away from the black holes.

“This is the first time we have been able to link the launching of the corona to a flare,” said Dr Wilkins, who is the lead author of a new study on the findings accepted for publication in the Monthly Notices of the Royal Astronomical Society (arXiv.org preprint).

“Coronas are made up of highly energetic particles that generate X-ray light, but details about their appearance, and how they form, are unclear.”

Dr Wilkins and his colleagues have been using NASA’s Swift space telescope to regularly monitor Markarian 335 since 2007.

On 29 August 2014, the telescope caught a huge flare coming from the supermassive black hole in this galaxy. Eight days later, NASA’s NuSTAR set its X-ray eyes on the target, witnessing the final half of the flare event.

After careful scrutiny of the data, the scientists realized they were seeing the ejection and eventual collapse of the black hole’s corona.

“The corona gathered inward at first and then launched upwards like a jet,” Dr Wilkins explained.

“We still don’t know how jets in black holes form, but it’s an exciting possibility that this black hole’s corona was beginning to form the base of a jet before it collapsed.”

The corona gives off X-ray light that has a slightly different spectrum than the light coming from the disk around the black hole.

By analyzing a spectrum of X-ray light across a range of wavelengths observed by both Swift and NuSTAR, the team could tell that the corona X-ray light had brightened, and that this brightening was due to the motion of the corona.

The corona associated with the supermassive black hole in Markarian 335 was traveling at about 20% the speed of light.

When this happens, and the corona launches in our direction, its light is brightened in an effect called relativistic Doppler boosting.

Putting this all together, the results show that the X-ray flare from this black hole was caused by the ejected corona.

“The nature of the energetic source of X-rays we call the corona is mysterious, but now with the ability to see dramatic changes like this we are getting clues about its size and structure,” said Dr Fiona Harrison of the California Institute of Technology in Pasadena, who was not involved in the study.


Massive black holes flaring up time and again

The short and regular bursts in massive black hole systems known as quasi-periodic eruptions have intrigued — and puzzled — astronomers since their discovery. Two such sources recently discovered by SRG/eROSITA suggest that they could be the electromagnetic counterparts to a type of gravitational-wave sources called extreme mass-ratio inspirals.

Binaries are some of the most ubiquitous systems in the Universe. Stars orbiting stars. Stars, or what are left of them, orbiting black holes. Black holes orbiting black holes. But perhaps one of the most unusual is a type of system known as an extreme mass-ratio inspiral (EMRI), which is a binary system with — you’ve guessed it — an extreme mass ratio between the two objects of about 10,000:1 or higher 1 . It is thought to be made up of a white dwarf, a neutron star or a stellar-mass black hole orbiting and slowly spiralling into a massive black hole located in the centre of a galaxy. These systems are some of the main sources of millihertz gravitational waves expected for the Laser Interferometer Space Antenna (LISA) 2 , the future space-borne gravitational-wave observatory. But what would be even more exciting would be if we could also observe these systems with our telescopes and receive astrophysical information from them using the two fundamentally different, yet complementary, messengers of gravitational waves and electromagnetic radiation. Writing in Nature, Riccardo Arcodia and collaborators 3 have reported the discovery of two ‘quasi-periodic eruptions’ (QPEs) and presented intriguing evidence that these new phenomena of short and regular X-ray flares, which were first reported in 2019 4 , could be the electromagnetic radiation emitted by EMRIs.


Supermassive black holes devour gas just like their petite counterparts

As a supermassive black hole consumed a star, researchers were surprised it exhibited properties that were similar to that of much smaller, stellar-mass black holes. Credit: Christine Daniloff, MIT

On Sept. 9, 2018, astronomers spotted a flash from a galaxy 860 million light years away. The source was a supermassive black hole about 50 million times the mass of the sun. Normally quiet, the gravitational giant suddenly awoke to devour a passing star in a rare instance known as a tidal disruption event. As the stellar debris fell toward the black hole, it released an enormous amount of energy in the form of light.

Researchers at MIT, the European Southern Observatory, and elsewhere used multiple telescopes to keep watch on the event, labeled AT2018fyk. To their surprise, they observed that as the supermassive black hole consumed the star, it exhibited properties that were similar to that of much smaller, stellar-mass black holes.

The results, published today in the Astrophysical Journal, suggest that accretion, or the way black holes evolve as they consume material, is independent of their size.

"We've demonstrated that, if you've seen one black hole, you've seen them all, in a sense," says study author Dheeraj "DJ" Pasham, a research scientist in MIT's Kavli Institute for Astrophysics and Space Research. "When you throw a ball of gas at them, they all seem to do more or less the same thing. They're the same beast in terms of their accretion."

Pasham's co-authors include principal research scientist Ronald Remillard and former graduate student Anirudh Chiti at MIT, along with researchers at the European Southern Observatory, Cambridge University, Leiden University, New York University, the University of Maryland, Curtin University, the University of Amsterdam, and the NASA Goddard Space Flight Center.

When small stellar-mass black holes with a mass about 10 times our sun emit a burst of light, it's often in response to an influx of material from a companion star. This outburst of radiation sets off a specific evolution of the region around the black hole. From quiescence, a black hole transitions into a "soft" phase dominated by an accretion disk as stellar material is pulled into the black hole. As the amount of material influx drops, it transitions again to a "hard" phase where a white-hot corona takes over. The black hole eventually settles back into a steady quiescence, and this entire accretion cycle can last a few weeks to months.

Physicists have observed this characteristic accretion cycle in multiple stellar-mass black holes for several decades. But for supermassive black holes, it was thought that this process would take too long to capture entirely, as these goliaths are normally grazers, feeding slowly on gas in the central regions of a galaxy.

"This process normally happens on timescales of thousands of years in supermassive black holes," Pasham says. "Humans cannot wait that long to capture something like this."

But this entire process speeds up when a black hole experiences a sudden, huge influx of material, such as during a tidal disruption event, when a star comes close enough that a black hole can tidally rip it to shreds.

"In a tidal disruption event, everything is abrupt," Pasham says. "You have a sudden chunk of gas being thrown at you, and the black hole is suddenly woken up, and it's like, 'whoa, there's so much food—let me just eat, eat, eat until it's gone.' So, it experiences everything in a short timespan. That allows us to probe all these different accretion stages that people have known in stellar-mass black holes."

In September 2018, the All-Sky Automated Survey for Supernovae (ASASSN) picked up signals of a sudden flare. Scientists subsequently determined that the flare was the result of a tidal disruption event involving a supermassive black hole, which they labeled TDE AT2018fyk. Wevers, Pasham, and their colleagues jumped at the alert and were able to steer multiple telescopes, each trained to map different bands of the ultraviolet and X-ray spectrum, toward the system.

The team collected data over two years, using X-ray space telescopes XMM-Newton and the Chandra X-Ray Observatory, as well as NICER, the X-ray-monitoring instrument aboard the International Space Station, and the Swift Observatory, along with radio telescopes in Australia.

"We caught the black hole in the soft state with an accretion disk forming, and most of the emission in ultraviolet, with very few in the X-ray," Pasham says. "Then the disk collapses, the corona gets stronger, and now it's very bright in X-rays. Eventually there's not much gas to feed on, and the overall luminosity drops and goes back to undetectable levels."

The researchers estimate that the black hole tidally disrupted a star about the size of our sun. In the process, it generated an enormous accretion disk, about 12 billion kilometers wide, and emitted gas that they estimated to be about 40,000 Kelvin, or more than 70,000 degrees Fahrenheit. As the disk became weaker and less bright, a corona of compact, high-energy X-rays took over as the dominant phase around the black hole before eventually fading away.

"People have known this cycle to happen in stellar-mass black holes, which are only about 10 solar masses. Now we are seeing this in something 5 million times bigger," Pasham says.

"The most exciting prospect for the future is that such tidal disruption events provide a window into the formation of complex structures very close to the supermassive black hole such as the accretion disk and the corona," says lead author Thomas Wevers, a fellow at the European Southern Observatory. "Studying how these structures form and interact in the extreme environment following the destruction of a star, we can hopefully start to better understand the fundamental physical laws that govern their existence."

In addition to showing that black holes experience accretion in the same way, regardless of their size, the results represent only the second time that scientists have captured the formation of a corona from beginning to end.

"A corona is a very mysterious entity, and in the case of supermassive black holes, people have studied established coronas but don't know when or how they formed," Pasham says. "We've demonstrated you can use tidal disruption events to capture corona formation. I'm excited about using these events in the future to figure out what exactly is the corona."


Supermassive Black Hole Devours Passing Star – Exhibits Properties That Surprise Astronomers

On September 9, 2018, astronomers spotted a flash from a galaxy 860 million light years away. The source was a supermassive black hole about 50 million times the mass of the sun. Normally quiet, the gravitational giant suddenly awoke to devour a passing star in a rare instance known as a tidal disruption event. As the stellar debris fell toward the black hole, it released an enormous amount of energy in the form of light.

Researchers at MIT, the European Southern Observatory, and elsewhere used multiple telescopes to keep watch on the event, labeled AT2018fyk. To their surprise, they observed that as the supermassive black hole consumed the star, it exhibited properties that were similar to that of much smaller, stellar-mass black holes.

The results, published on May 17, 2021, in the Astrophysical Journal, suggest that accretion, or the way black holes evolve as they consume material, is independent of their size.

“We’ve demonstrated that, if you’ve seen one black hole, you’ve seen them all, in a sense,” says study author Dheeraj “DJ” Pasham, a research scientist in MIT’s Kavli Institute for Astrophysics and Space Research. “When you throw a ball of gas at them, they all seem to do more or less the same thing. They’re the same beast in terms of their accretion.”

Pasham’s co-authors include principal research scientist Ronald Remillard and former graduate student Anirudh Chiti at MIT, along with researchers at the European Southern Observatory, Cambridge University, Leiden University, New York University, the University of Maryland, Curtin University, the University of Amsterdam, and the NASA Goddard Space Flight Center.

A stellar wake-up

When small stellar-mass black holes with a mass about 10 times our sun emit a burst of light, it’s often in response to an influx of material from a companion star. This outburst of radiation sets off a specific evolution of the region around the black hole. From quiescence, a black hole transitions into a “soft” phase dominated by an accretion disk as stellar material is pulled into the black hole. As the amount of material influx drops, it transitions again to a “hard” phase where a white-hot corona takes over. The black hole eventually settles back into a steady quiescence, and this entire accretion cycle can last a few weeks to months.

Physicists have observed this characteristic accretion cycle in multiple stellar-mass black holes for several decades. But for supermassive black holes, it was thought that this process would take too long to capture entirely, as these goliaths are normally grazers, feeding slowly on gas in the central regions of a galaxy.

“This process normally happens on timescales of thousands of years in supermassive black holes,” Pasham says. “Humans cannot wait that long to capture something like this.”

But this entire process speeds up when a black hole experiences a sudden, huge influx of material, such as during a tidal disruption event, when a star comes close enough that a black hole can tidally rip it to shreds.

“In a tidal disruption event, everything is abrupt,” Pasham says. “You have a sudden chunk of gas being thrown at you, and the black hole is suddenly woken up, and it’s like, ‘whoa, there’s so much food — let me just eat, eat, eat until it’s gone.’ So, it experiences everything in a short timespan. That allows us to probe all these different accretion stages that people have known in stellar-mass black holes.”

A supermassive cycle

In September 2018, the All-Sky Automated Survey for Supernovae (ASASSN) picked up signals of a sudden flare. Scientists subsequently determined that the flare was the result of a tidal disruption event involving a supermassive black hole, which they labeled TDE AT2018fyk. Wevers, Pasham, and their colleagues jumped at the alert and were able to steer multiple telescopes, each trained to map different bands of the ultraviolet and X-ray spectrum, toward the system.

The team collected data over two years, using X-ray space telescopes XMM-Newton and the Chandra X-Ray Observatory, as well as NICER, the X-ray-monitoring instrument aboard the International Space Station, and the Swift Observatory, along with radio telescopes in Australia.

“We caught the black hole in the soft state with an accretion disk forming, and most of the emission in ultraviolet, with very few in the X-ray,” Pasham says. “Then the disk collapses, the corona gets stronger, and now it’s very bright in X-rays. Eventually there’s not much gas to feed on, and the overall luminosity drops and goes back to undetectable levels.”

The researchers estimate that the black hole tidally disrupted a star about the size of our sun. In the process, it generated an enormous accretion disk, about 12 billion kilometers wide, and emitted gas that they estimated to be about 40,000 Kelvin, or more than 70,000 degrees Fahrenheit. As the disk became weaker and less bright, a corona of compact, high-energy X-rays took over as the dominant phase around the black hole before eventually fading away.

“People have known this cycle to happen in stellar-mass black holes, which are only about 10 solar masses. Now we are seeing this in something 5 million times bigger,” Pasham says.

“The most exciting prospect for the future is that such tidal disruption events provide a window into the formation of complex structures very close to the supermassive black hole such as the accretion disk and the corona,” says lead author Thomas Wevers, a fellow at the European Southern Observatory. “Studying how these structures form and interact in the extreme environment following the destruction of a star, we can hopefully start to better understand the fundamental physical laws that govern their existence.”

In addition to showing that black holes experience accretion in the same way, regardless of their size, the results represent only the second time that scientists have captured the formation of a corona from beginning to end.

“A corona is a very mysterious entity, and in the case of supermassive black holes, people have studied established coronas but don’t know when or how they formed,” Pasham says. “We’ve demonstrated you can use tidal disruption events to capture corona formation. I’m excited about using these events in the future to figure out what exactly is the corona.”

Reference: “Rapid Accretion State Transitions following the Tidal Disruption Event AT2018fyk” by T. Wevers, D. R. Pasham, S. van Velzen, J. C. A. Miller-Jones, P. Uttley, K. C. Gendreau, R. Remillard, Z. Arzoumanian, M. Löwenstein and A. Chiti, 17 May 2021, Astrophysical Journal.
DOI: 10.3847/1538-4357/abf5e2

This research was partially supported by the Australian Government through the Australian Research Council’s Discovery Projects funding scheme.


Clearing up a supermassive (black hole) confusion

The Mercator telescope on La Palma, Spain. Image credit: Péter I. Pápics

Black holes are among the most enigmatic objects in our universe. These mysterious celestial bodies do not emit any light of their own and are thus incredibly difficult to spot. In fact, one can only detect black holes based on the effects that they have on their surroundings. Black-holes come in various flavors and sizes, from 'small' stellar-mass black holes to supermassive black holes found in the center of galaxies. Stellar-mass black holes are the final remnants of massive stars, born more than 20 to 30 times the mass of our Sun and should only form in certain mass ranges according to current theory. In this context, the claimed discovery, published in the distinguished journal Nature in November 2019, of a black hole 70 times more massive than our Sun caught the attention of the astronomical community.

The system in question, LS V +22 25 or LB-1 in short, was claimed to be a double-star system consisting of an 8 solar mass star and a 70 solar mass black hole that orbit around one another in just 80 days, very much the same way as planets orbit around stars. The data used in the original study showed two spectral signatures that moved in different ways: one clear signature belonging to the star and another, more subtle, that was interpreted as belonging to material around the black hole, thus tracing its orbital motion. Based on the motion of these two signatures, the original authors reached their controversial conclusion.

"A stellar black hole this massive challenges everything we know about massive star evolution," says Michael Abdul-Masih, a Ph.D. student from the KU Leuven Institute of Astronomy in Belgium. "Theory tells us that in this mass range, when a star dies it should completely annihilate itself without leaving anything behind, and certainly not such a massive black hole."

The interpretation of the second signature has since come under scrutiny. Using higher-resolution data from the Flemish-funded Mercator Telescope on the island of La Palma (Spain), the KU Leuven team ran several simulations and concluded that the original interpretation of the system was in fact incorrect.

"As we examined the available data more carefully, we began to realize that something didn't seem quite right" explains Michael Abdul-Masih. "The second signature did not behave as we expected it to. This is when I realized that maybe this second signature is not moving at all, but only appears to do so because of the movement of the star." "It is a little like the fake impression of moving you get while sitting in a train and the train next to you starts moving while you are not.", explains Prof. Hugues Sana of KU Leuven further.

The team quickly tested this interpretation and found that it indeed was able to reproduce the observations without the need of such a massive black hole in the system.

"It was quite exciting when we first saw the results. The simulations matched the observations perfectly and we were able to prove that LB-1 does not contain a 70 solar mass black hole as originally thought," concludes Julia Bodensteiner, another Ph.D. student in the team of Prof. Sana.

The findings of Ph.D. student Abdul-Masih appear in the prestigious journal Nature this week and solve the riddle posed by the claimed presence of a massive black-hole in LB1. Even though astronomers can breathe a sigh of relief that LB-1 does not violate stellar evolution theory, this system is indeed remarkable and will surely be the subject of additional studies in the future.

Michael Abdul-Masih et al. On the signature of a 70-solar-mass black hole in LB-1, Nature (2020). DOI: 10.1038/s41586-020-2216-x


DST astronomers trace huge optical flare from supermassive black hole discovered in the 1960s

Indian astronomers have reported one of the strongest flares from a feeding supermassive black hole or blazar called BL Lacertae, analysis of which can help trace the mass of the black hole and the source of this emission, the Department of Science and Technology said on Saturday. Such analysis can provide a lead to probe mysteries and trace events at different stages of evolution of the Universe, it said. Blazars or feeding supermassive black holes in the heart of distant galaxies receive a lot of attention from the astronomical community because of their complicated emission mechanism. They emit jets of charged particles travelling nearly at the speed of light, making them one of the most luminous and energetic objects in the known universe.

"BL Lacertae blazar is 10 million light-years away and is among the 50 most prominent blazars that can be observed with the help of a relatively small telescope. It was among the 3 to 4 blazars that was predicted to be experiencing flares by the Whole Earth Blazar Telescope (WEBT), an international consortium of astronomers," the statement said.

Illustration of a shock wave (bright blob in the upper jet) after a
spiral path (yellow) as it moves away from the black hole and through a section of
the jet where the magnetic field (light blue curved lines) is wound up in a coil. Image: Cosmovision/Instituto de Astronomia

A team of astronomers led by Alok Chandra Gupta from Aryabhatta Research Institute of Observational Sciences (ARIES), an institute of the Department of Science & Technology, who has been following the blazar since October 2020 as part of an international observational campaign detected the exceptionally high flare on January 16 with the help of Sampurnanand Telescope (ST) and 1.3 m Devasthal Fast Optical Telescopes located in Nainital.

The data collected from the flare observed will help calculation of the black hole mass, size of emission region, and mechanism of the emission from one of the oldest astronomical objects known, hence opening a door to the origin and evolution of the Universe, it added.

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Watch the video: How to Spot a Supermassive Black Hole. Supermassive Black Holes. BBC Studios (November 2022).