This is an image of a series of Chandra images that has allowed scientists to trace the evolution of large-scale X-ray jets produced by a black hole in a binary star system. As the schematic shows, gaseous matter pulled from a normal star forms a disk around the black hole. The gas is heated to temperatures of millions of degrees, and intense electromagnetic forces in the disk can expel jets of high-energy particles. (Image for representation only. Please see actual image below.)

 

(Photo : NASA/Getty Images)

Astronomers identified for the first time an intermediate-mass black hole also called "middleweight" black hole hiding at the center of the globular star cluster 47 Tucanae. It weighs about 2,200 times the mass of the Sun.

The world's first discovery was described in the science journal Nature on Feb. 9, 2017. It was led by Dr. Bulent Kiziltan of the Harvard-Smithsonian Center for Astrophysics in the United States and other colleagues. This discovery is the first proof that the intermediate-mass black hole exists in space, according to ABC News.

Dr. Kiziltan said that they want to find intermediate-mass black holes because they are the missing link between stellar-mass and supermassive black holes. He further said that they may be primordial seeds that grew into the monsters they see in the centers of galaxies today.

There are two pieces of evidence of the existence of this middleweight black hole. First is the overall motions of stars in the cluster, in which it so dense that the heavier stars tend to sink at the center of the cluster. Meanwhile, the intermediate-mass black hole hiding at the center of the cluster acts like a cosmic spoon and stirs the pot. This caused the stars to slingshot to higher speeds and greater distances. Then, the team was able to employ computer simulations of stellar motions and distances and likened them with visible-light observations and finally finds evidence for this gravitational stirring.

The second evidence comes from pulsars and dead stars that radio signals could be easily identified. They were also flung by the gravity of the central intermediate-mass black hole and caused them to be at greater distances from the center of the cluster.

With these two pieces of evidence, the astronomers discovered the presence of an intermediate-mass black hole of about 2,200 solar masses in the 47 Tucanae. This is 12-billion-year-old star cluster located 13,000 lightyears away from Earth in the southern constellation of Tucana the Toucan, according to Phys.org. </s> Intermediate-mass black holes should help us to understand the evolutionary connection between stellar-mass and super-massive black holes1. However, the existence of intermediate-mass black holes is still uncertain, and their formation process is therefore unknown2. It has long been suspected that black holes with masses 100 to 10,000 times that of the Sun should form and reside in dense stellar systems3,4,5,6. Therefore, dedicated observational campaigns have targeted globular clusters for many decades, searching for signatures of these elusive objects. All candidate signatures appear radio-dim and do not have the X-ray to radio flux ratios required for accreting black holes7. Based on the lack of an electromagnetic counterpart, upper limits of 2,060 and 470 solar masses have been placed on the mass of a putative black hole in 47 Tucanae (NGC 104) from radio and X-ray observations, respectively8,9. Here we show there is evidence for a central black hole in 47 Tucanae with a mass of solar masses when the dynamical state of the globular cluster is probed with pulsars. The existence of an intermediate-mass black hole in the centre of one of the densest clusters with no detectable electromagnetic counterpart suggests that the black hole is not accreting at a sufficient rate to make it electromagnetically bright and therefore, contrary to expectations, is gas-starved. This intermediate-mass black hole might be a member of an electromagnetically invisible population of black holes that grow into supermassive black holes in galaxies. </s> An intermediate-mass black hole might be lurking within a dense stellar cluster — a discovery that could point toward how these oddities form.

Every Friday Bülent Kızıltan heads to a local coffee shop. There, Kızıltan (Harvard-Smithsonian Center for Astrophysics), who is a self-described “overly curious person,” meets with scientists, artists and philosophers from different disciplines across the Cambridge and Boston area. His goal is to enrich himself intellectually.

That’s how he found himself deep in conversation with a cognitive scientist one afternoon who introduced him to a mathematical tool called Kullback–Leibler divergence. Originally developed by two mathematicians and cryptanalysts at the National Security Agency in the 1950s, the tool attempts to extract information from incomplete data.

Perhaps it was the stimulating effects of the freshly brewed cup of joe, but Kızıltan quickly realized that this tool could also be used when observing a dense stellar cluster — a messy environment chockfull of hundreds of thousands of stars where the center is hidden from view. It was the first step toward a paper published today in the journal Nature that provides the best evidence yet that a globular cluster might harbor an intermediate-mass black hole.

"Weighing" a Hidden Black Hole

Few intermediate-mass black holes have been observed before. In fact, skeptics might argue that none of these black holes — which theoretically lie in the range between those that are just a few times the mass of our Sun and those that weigh millions to billions of times the Sun — even exist.

The issue is two-fold. First, there’s no obvious, direct way for these objects to form. Second, the evidence that they exist has been hazy at best.

But with this new mathematical tool in hand, Kızıltan knew he could do better. He set his eyes on the globular cluster 47 Tucanae, located roughly 15,000 light-years away in the southern constellation Tucana. The cluster, which appears roughly the size of the full Moon, is one of the most massive globular clusters in the galaxy, with millions of stars.

In order to probe those stars, Kızıltan and his colleagues first built a realistic model of 47 Tucanae. Then, they measured the locations of 25 pulsars throughout the globular cluster. These rapidly rotating neutron stars sweep electromagnetic radiation across Earth with every spin at a rate so reliable they rival atomic clocks. This (plus the fact that they emit radio waves, as opposed to visible light) enabled the team to probe deeper into the typically invisible depths of the globular cluster.

The pulsars, they found, are on the move. They’re spinning around the center of the cluster rapidly — too rapidly given the number of central stars alone. Using their new mathematical tool, Kızıltan and his colleagues compared those pulsars’ oddly quick movements with their simulation in order to determine that an intermediate-mass black hole, some 2,200 times the mass of the Sun, must be lurking in the cluster’s center, governing the pulsars’ motions.

Runaway Collisions or Dangerous Tangos?

But Cole Miller (University of Maryland), who was not involved in the study, doesn’t think that the new evidence will convince every skeptic.

“Most scientists would like to see strong evidence,” he says. “Because if these objects exist, they will have implications for the formation of the earliest massive black holes. They will have implications about stellar dynamics. And they will have implications about the evolution of very massive stars. All of this is frontier research and you don't want to be jumping on the band wagon too early.”

The main issue is that astronomers are at a loss to explain how these intermediate-mass black holes can form. Miller’s favorite hypothesis enlists runaway stellar collisions. Essentially, the heaviest stars sink to the center of the globular cluster, where they are most likely to collide and merge with other heavy stars, forming even bigger stars. And because a star’s gravitational pull increases with its size and mass, so does its chance of further stellar collisions. This effect snowballs until a massive star rests in the center of the globular cluster.

But how this massive star evolves is not fully understood, says Kayhan Gültekin (University of Michigan) who was not involved in the study. “Standard stellar theory doesn’t apply to these objects. A lot of turning this merged star-like object into a black hole is based on analogies with stellar evolution rather than detailed calculations of how it would actually evolve.”

Luckily, the competing theory doesn’t need to invoke strange astrophysics. Here, stars evolve into black holes, which sink to the center of the cluster where one enters into a binary orbit with another. Through interactions with other black holes, that duo shrinks until it merges, creating a more massive black hole. This single black hole picks up another companion and the process begins anew, until there’s only one massive black hole in the center of the globular cluster.

Unfortunately, there are issues with this theory too. In the interactions between the black hole binary and the third black hole, energy is transferred to the third black hole. And if enough energy is transferred, the third black hole could get kicked out of the system entirely — a huge problem when you’re trying to build a massive black hole.

Although there are other theories that could explain how intermediate-mass black holes arise, only these two rely on the densely packed environment of a globular cluster.

“The fact that this black hole exists in 47 Tucanae, might mean that one or both of those theories is correct,” says Gültekin, who is hopeful that both theories will receive rejuvenated attention in light of the latest discovery.

Reference:

B. Kızıltan et al. “An Intermediate-Mass Black Hole in the Centre of the Globular Cluster 47 Tucanae.”Nature, February 9, 2017. </s> An international team of scientists - including 21 researchers from The University of Western Australia - has detected gravitational waves for the third time in history. The first time was in September 2015, then again in December 2015.

Gravitational waves are waves of energy, ripples in the fabric of space-time. The discovery of the first wave proved a prediction by Einstein 100 years ago.

The newfound black hole, formed by the pair's merger, has a mass about 49 times that of our sun. This fills in a gap between the masses of the two merged black holes detected previously by LIGO, which had solar masses of 62 (first detection) and 21 (second detection).

These collisions produce more power during the instant before the black holes merge, than is radiated as light by all the stars and galaxies in the universe at any given time. The recent detection is the farthest yet, with the black holes located about 3 billion light-years away.

The black holes in the first and second detections are located 1.3 and 1.4 billion light-years away, respectively.

The third and most recent detection, called GW170104, was made on January 4 this year. The latest finding solidifies the case for a new class of black hole pairs, or binary black holes, with masses that are larger than what had been seen before by the Laser Interferometer Gravitational-wave Observatory (LIGO) detectors.

Professor David Blair, from UWA's School of Physics, said the event released more energy in its last few orbits than that of rest of the entire universe.

"Yet when the ripples passed the LIGO detector they made it vibrate by just one attometer, or 0.000000000000000001 metres," Professor Blair said.

Despite this tiny displacement, the scientists were able to demonstrate the black holes exhibited a property known as "spin".

"This is the first time that we have evidence that the black holes may not be aligned, giving us just a tiny hint that pairs of black holes may form in dense stellar clusters," Professor Blair said.

Postdoctoral Fellow Qi Chu, from UWA's School of Physics, is part of a team led by OzGrav Chief Investigator Professor Linqing Wen that is racing to create faster ways to crunch the LIGO data to minimise the time between the gravitational waves hitting earth and an alert being sent out for follow-up observations.

"The LIGO detector lets us feel the gravitational wave, and we are on a mission to see the source of the event by looking through powerful telescopes," Ms Chu said.

An international group of researchers, including the Australian International Gravitational Research Centre, is also investigating how to fine-tune the sensitivity of the gravitational waves detector, leading to improved detection of future gravitational waves and electromagnetic observational, and potentially more exotic sources.

LIGO is funded by the National Science Foundation (NSF), and operated by MIT and Caltech, which conceived and built the project. Financial support for the Advanced LIGO project was led by NSF with Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council) and Australia (Australian Research Council) making significant commitments and contributions to the project.

More than 1,000 scientists from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration. LIGO partners with the Virgo Collaboration, a consortium including 280 additional scientists throughout Europe supported by the Centre National de la Recherche Scientifique (CNRS), the Istituto Nazionale di Fisica Nucleare (INFN), and Nikhef, as well as Virgo's host institution, the European Gravitational Observatory.

The ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) is funded by the Australian Government through the Australian Research Council Centres of Excellence funding scheme. OzGrav is a partnership between Swinburne University (host of OzGrav headquarters), the Australian National University, Monash University, University of Adelaide, University of Melbourne, and University of Western Australia, along with other collaborating organisations in Australia and overseas. </s> For the third time, scientists have detected a spacetime rumble caused by a violent collision of two black holes. The Laser Interferometer Gravitational-wave Observatory (LIGO) made the detection, determining that the two black holes merged to create one large black hole in a galaxy about 3 billion light-years away.

"We have observed – on the 4th of January, 2017 – another massive black hole-black hole binary coalescence; the in-spiral and merging of black holes 20 and 30 times the mass of our sun," Dave Shoemaker, a senior research scientist who works at Massachusetts Institute of Technology (MIT) and the spokesperson for the LIGO Scientific Collaboration, told reporters during a special news briefing on Wednesday (May 31).

This gargantuan black hole smashup created an even more massive spinning black hole, approximately 49 times the mass of our sun. In an instant, the equivalent mass twice that of our sun was converted directly into gravitational waves — briefly producing more energy than all the energy that is radiated as light by all the galaxies in the universe at any moment, LIGO scientists say.

After many years of planning, development and construction, LIGO took its first observations in 2002. However, it wasn't until Sept. 14, 2015, that the first historic detection of gravitational waves — an event called "GW150914" — was made. That happened after LIGO underwent upgrades (known as Advanced LIGO) to boost its sensitivity. Then, a second detection ("GW151226") followed a few months later in December, confirming that the first discovery was no fluke.

Now, the LIGO Scientific Collaboration — which consists of over a thousand scientists around the world — has confirmed the third gravitational wave detection ("GW170104"), meaning we're at the cusp of a completely new kind of astronomy.

All the gravitational waves detected so far have been created by the collision of stellar-mass black holes of varied sizes. These are black holes that are a few to a few dozen times the mass of our sun that were likely formed by the death of very massive stars after they'd run out of fuel and exploded as supernovas billions of years ago. Advanced LIGO has reached a crossroads in our gravitational wave search, finally reaching a sensitivity that can detect when very distant black holes collide, creating faint gravitational waves that we now know fill our universe.

The 2015 events were caused by mergers creating black holes 62 and 21 solar masses in galaxies 1.3 and 1.4 billion light-years away, respectively. (Note: As gravitational waves travel at the speed of light these mergers happened 1.3 and 1.4 billion years ago.) This latest detection originated from a merger creating a black hole of 49 solar masses (another "heavy" black hole like the first one), but the merger happened over twice as far away than previous events.

"What this means is that we now have a second candidate in the "heavy" black hole category," says Bangalore Sathyaprakash, of Penn State and Cardiff University and a member of the LIGO Scientific Collaboration.

This is important as, before LIGO made its first detection (a 62 solar mass black hole) and its most recent one (a 49 solar mass black hole), there was no observational evidence that these large black holes even existed. This is an incredible early discovery. Scientists have revealed a brand-new type of large black hole in only three detections.

Things are about to get even more exciting as LIGO undergoes more planned upgrades and other observatories join the hunt for gravitational waves.

"We should expect to see one binary merger event per day once LIGO's designed sensitivity is reached," says Sathyaprakash.

When gravitational waves are detected the conditions of the colliding black holes at the time of the merger can be studied.

"In our analysis, we cannot measure the spins of the individual black holes very well, but we can tell if the black holes are generally spinning in the same direction as the orbital motion," says astrophysicist Laura Cadonati, LIGO Scientific Collaboration deputy spokesperson from Georgia Tech.

But an idea of the individual black hole's spin relative to one another can be figured out by studying the "fingerprint" of the gravitational wave signal, says Cadonati.

Theoretical models of merging black holes indicate that if the two black holes' spins are not aligned, the merging event will happen faster than if the spins are aligned. Also, additional wobbles in the signal are predicted as two spin-aligned black holes get close and begin to merge.

Spin-aligned black holes were likely sibling stars. Both would have been born from massive stars that evolved in close proximity in ancient star factories as a binary pair, eventually dying as supernovas.

But in this most recent event, the merging occurred relatively quickly and no additional oscillations were observed, meaning the two black holes were likely not spin-aligned and probably didn't form together. This gives a clue to their origin: Rather than being formed from sibling binary stars, they were strangers and evolved independently, drifting toward one another in the center of a dense stellar cluster where they eventually merged.

"This has implications for astrophysics ... while we cannot say with certainty, this finding likely favors the theory that these two black holes formed separately in a dense stellar cluster, sank to the core of the cluster and then paired up, rather than being formed together from the collapse of two already paired stars," adds Cadonati.

As black holes are gravitational monsters, they're governed by Einstein's general relativity, so by studying the gravitational waves they produce when they collide, scientists also can study the waves for an effect known as "dispersion." For example, when light travels through a prism, the different wavelengths will travel at different speeds through the glass. This causes dispersion in the beam of light — this is the mechanism that creates a rainbow.

General relativity forbids dispersion from happening to gravitational waves, however. This latest signal traveled across a record 3 billion light-years of spacetime to reach Earth, and LIGO didn't detect any dispersion effects.

"It looks like Einstein was right – even for this new event, which is about two times farther away than our first detection," says Cadonati in a statement. "We can see no deviation from the predictions of general relativity, and this greater distance helps us to make that statement with more confidence."

A New Window to the 'Dark Universe'

Einstein's famous theory of general relativity predicts the existence of gravitational waves, but it's taken humanity over a century to develop the technological know-how to build a detector sensitive enough to perceive them. When an energetic event occurs (like a black hole merger or neutron star collision), spacetime becomes violently disturbed and energy is carried away from the event in the form of gravitational waves — like ripples traveling across the water's surface after dropping a pebble in a pond.

But to detect these waves, astronomers need to build an observatory that can detect incredibly minuscule wobbles in the fabric of spacetime as these waves travel through our planet. Gravitational waves are not part of the electromagnetic spectrum; they cannot be detected by ordinary telescopes that are only sensitive to light.

To open the window to this "dark universe," physicists build gravitational wave detectors like LIGO that reflect incredibly precise lasers along 2.5 mile-long (4 kilometer-long) "L"-shaped tunnels. These tunnels are shielded from external vibrations caused by wind, traffic, tectonic activity and other terrestrial interference. Through a method known as laser interferometry, the distance between the reflecting mirrors inside the tunnel can be measured to a very high precision. Should a gravitational wave travel through our planet, a tiny change in distance may be recorded by the interferometer – this represents the minute squeezing and stretching of spacetime that occurs as gravitational waves propagate.

It's as if physicists have created a virtual tripwire that notifies us when an invisible gravitational wave intruder rumbles local spacetime.

One detector isn't enough to confirm a gravitational wave event, however. In the case of LIGO, one detector is located in Hanford, Washington, and another is located in Livingston, Louisiana — separated by 1,865 miles (3,002 kilometers). Only when the same event is detected by both locations can scientists confirm a gravitational wave signal. Two detectors can even determine a rough direction as to where the wave was traveling from, but if more detectors are added to the network, astronomers hope to eventually pinpoint, with increasing precision, where they originate.

More gravitational wave observatories are planned, and the European Virgo detector, located near Pisa, Italy, is currently undergoing commissioning. Once online, Virgo will be used in conjunction with LIGO to boost observational power of gravitational waves and allow better localization of the cosmic events causing the signals.

Now that the existence of gravitational waves has been confirmed, and astronomers are detecting more black hole mergers, we are entering a new era for astronomy. This is gravitational wave astronomy, where the dark universe will finally be revealed. </s> 'Middleweight' black hole discovered in space in world-first, Queensland scientist says

A Queensland scientist has played a vital role in the world-first discovery of a "middleweight" black hole in space, spending 40 years searching the universe to find it.

University of Queensland astronomer Associate Professor Holger Baumgardt said it was the missing link between small and super-sized black holes.

Dr Baumgardt said the discovery would help astronomers understand galaxies and how galaxies have formed and evolved.

He said black holes were normally either small and weighed a few times the Sun's mass, or supermassive, and weigh millions of times the Sun's mass.

But this study showed the first proof of an intermediate-mass black hole existing — weighing 2,200 times the mass of the Sun.

The researchers, led by Dr Bulent Kiziltan of the Harvard-Smithsonian Centre for Astrophysics in the United States, relied on computer simulations by the Queensland scientists to look for clues in space.

By employing simulations of stellar motions and distances, and comparing them with visible-light observations, the team found evidence for just this sort of gravitational stirring.

He said the second line of evidence came from pulsars, compact remnants of dead stars with radio signals that were easily detectable.

"These objects were also flung about due to the gravitational influence of the central intermediate-mass black hole, causing them to be found at greater distances from the cluster's centre than would be expected if no black hole existed," Dr Baumgardt said.

The discovery was announced today in the journal Nature, revealing the black hole hid at the centre of the 12-billion-year-old globular 47 Tucanae star cluster.

It is 13,000 light years from Earth in the southern constellation of Tucana the Toucan.

It contains 3 million stars and holds about two dozen pulsars that are important targets of this investigation.

In their paper, the researchers said 47 Tucanae had been examined previously for a central black hole, without success.

Dr Kiziltan said in most cases, a black hole was found by looking for X-rays emanating from a hot disk of material swirling around the black hole.

This method only worked if the black hole was actively feeding on nearby gas.

"The centre of 47 Tucanae is gas-free, effectively starving any black hole that might lurk there," Dr Kiziltan said.

"A supermassive black hole at the centre of the Milky Way gives clues to its presence by its influence on nearby stars.

"Years of infrared observations have shown a handful of stars at our galactic centre whipping around an invisible object with a strong gravitational tug.

"But the crowded centre of 47 Tucanae makes it impossible to watch the motions of individual stars."

This was why the hunt for the "missing link" across the cosmos was so challenging, he said.

However, the discovery would not help find out more about life in space, Dr Baumgardt said.

"Anything which comes too close to the black hole will basically fall into the black hole and have no chance of ever getting out again."

The researchers said their discovery would help them unlock the link between the smaller mass black holes and super ones that could be found in the centre of galaxies.

"Of course we got very excited because we've been looking for black holes for a very long time," Dr Baumgardt said.

"We are already working on a second cluster to find a second 'middleweight' black hole."

Researchers said the fact this black hole had eluded detection for so long suggested black holes of similar masses could be hiding in other globular clusters. </s> Two massive black holes colliding into each other created ripples in space and time, known as gravitational waves, which have been detected at the furthest distance yet, international physicists said Thursday.

The galactic mash-up which produced the gravitational waves occurred some three billion light-years away, and marks the science world's third observation of this phenomenon.

The finding further bolsters Einstein's 1915 theory of general relativity, and comes two years after these enigmatic ripples were first detected, said the report in the journal Physical Review Letters.

"It is remarkable that humans can put together a story, and test it, for such strange and extreme events that took place billions of years ago and billions of light-years distant from us," said David Shoemaker, spokesman for the Laser Interferometer Gravitational-wave Observatory (LIGO) Scientific Collaboration.

The group includes more than 1,000 international scientists who perform LIGO research together with the European-based Virgo Collaboration.

In all three cases, each of the twin detectors of LIGO detected gravitational waves from the tremendously energetic mergers of black hole pairs.

"These are collisions that produce more power than is radiated as light by all the stars and galaxies in the universe at any given time," said a LIGO statement.

The latest black hole collision, resulting in a detectable "chirp" of a gravitational wave, happened when two black holes merged, forming a new one that is about 49 times the mass of the Sun.

Its size is smack in the middle of the first such black hole merger detected by LIGO, at 62 solar masses, and the second which had 21.

"We have further confirmation of the existence of stellar-mass black holes that are larger than 20 solar masses -- these are objects we didn't know existed before LIGO detected them," said Shoemaker, a senior research scientist at the Massachusetts Institute of Technology (MIT).

The first-ever direct observation of gravitational waves was made in September 2015, and detected an event some 1.3 billion light-years away.

The second came shortly after, in December 2015, and was a distance of 1.4 billion light-years.

The third detection, called GW170104, was made on January 4, 2017.

"With the third confirmed detection of gravitational waves from the collision of two black holes, LIGO is establishing itself as a powerful observatory for revealing the dark side of the universe," says David Reitze of Caltech, executive director of the LIGO Laboratory.

"While LIGO is uniquely suited to observing these types of events, we hope to see other types of astrophysical events soon, such as the violent collision of two neutron stars."

LIGO's observations are carried out by twin detectors -- one in Hanford, Washington, and the other in Livingston, Louisiana.

The observatories, which use laser interferometers to sense the presence of gravitational waves, are operated by Caltech and MIT with funding from the National Science Foundation (NSF).

"It looks like Einstein was right -- even for this new event, which is about two times farther away than our first detection," said Laura Cadonati, an associate professor at the Georgia Institute of Technology.

"We can see no deviation from the predictions of general relativity, and this greater distance helps us to make that statement with more confidence." </s> In yet another historic moment, an international research team, including scientists from India, has announced the third detection of gravitational waves -- ripples in the fabric of space and time which were first predicted by Albert Einstein more than a century ago.

The Laser Interferometer Gravitational-wave Observatory (LIGO) in the US made the detection on January 4 this year, demonstrating that a new window in astronomy has been firmly opened.

Gravitational waves pass through Earth and can be "heard" by the extremely sensitive LIGO detectors.

As was the case with the first two detections, the waves were generated when two black holes merged to form a larger black hole.

"Our handful of detections so far is revealing an intriguing black hole population we did not know existed until now," said Northwestern University's Vicky Kalogera, a senior astrophysicist with the LIGO Scientific Collaboration (LSC).

The new detection, called GW170104, occurred during the ongoing second observing run of the Advanced LIGO detectors which began on November 30 last year.

The first direct observation of gravitational waves was made in September 2015 during the first observing run.

A second detection was made in December 2015.

The third detection is described in a new paper accepted for publication in the journal Physical Review Letters.

The publication has 40 authors from 11 Indian institutions.

IIT-Madras recently joined the LSC as one of the participating institutes, under the leadership of Dr Chandra Kant Mishra.

The Chennai Mathematical Institute has also been contributing to the activities under the leadership of Dr K.G. Arun.

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The group at IIT-Madras is involved in modelling the gravitational wave sources such as the ones which have been detected by the LIGO detectors so far as well as testing the consistency of the detected gravitational wave signals with the predictions of Einstein's general theory of relativity.

The third and latest detection points to merging black holes that are twice as far away from Earth as the two earlier pairs -- about three billion light-years away.

This time, the two black holes were unequal in size, one significantly lighter than the other. They merged into a black hole whose size is in the middle of the other two merged black hole pairs.

"Now we have three pairs of black holes, each pair ending their death spiral dance over millions or billions of years in some of the most powerful explosions in the universe. In astronomy, we say with three objects of the same type you have a class. We have a population, and we can do analysis," Kalogera added.

The newfound black hole, formed by the pair's merger, has a mass about 49 times that of our sun.

This fills in a gap between the masses of the two merged black holes detected previously by LIGO, which had solar masses of 62 (first detection) and 21 (second detection).

"We have further confirmation of the existence of black holes that are heavier than 20 solar masses, objects we didn't know existed before LIGO detected them," said David Shoemaker of MIT, the newly elected spokesperson for the LSC.

India is also working towards setting up its own LIGO observatory.

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The move received in-principle approval from the cabinet in February last year and has made rapid progress towards the plan to join these exciting scientific observations in 2024.

LIGO-India will greatly enhance the scientific capabilities of the international network of observatories for astronomy, primarily by enabling precise pointing to the location of the gravitational wave events in the sky.

Scientific and engineering teams at IPR Gandhinagar, IUCAA Pune and RRCAT Indore are actively engaged in the pre-construction activities of LIGO-India. </s> University of Columbia in New York reveals there could be 10,000 smaller black holes surrounding the supermassive black hole in the Milky Way's Galactic Center.

A new study by Columbia University suggests that 10,000 smaller black holes surround the supermassive black hole at the core of the Milky Way.

According to a report by Science Daily, researchers discovered a dozen black holes surrounding the supermassive black hole in the middle of the Milky Way, Sagittarius A. This supports predictions that smaller black holes surround a much larger black hole.

Chuck Hailey, the study’s lead author and a co-director of the university’s astrophysics lab, explains that studying the distribution makes it possible to learn the interaction between bigger black holes and the smaller black holes.

For years, scientists have been looking for evidence that much smaller black holes surround supermassive ones located at the core of large galaxies. The Columbia University study which appears in the April 5 issue of the journal Nature aims to shed light on this theory.

As Hailey explains, the most accessible place to prove this theory is by studying the closest supermassive black hole to Earth, Sagittarius A.

The most common method to look for black holes is to look for bursts of X-ray glow which occurs in some black hole binaries. According to Hailey, this is the obvious way to search for black holes located in the Galactic Center. However, bursts which are bright and strong enough can only be seen in 100 to 1,000 years. Hence, his team devised another method — looking for X-rays emitted by binaries that are in an inactive state. These emissions are fainter but steadier.

These emissions indicate the mating between a low mass star and a black hole, hence proving a more viable way of knowing what lies in the Galactic Center.

“Isolated, unmated black holes are just black — they don’t do anything. So looking for isolated black holes is not a smart way to find them either. But when black holes mate with a low mass star, the marriage emits X-ray bursts that are weaker, but consistent and detectable. If we could find black holes that are coupled with low mass stars and we know what fraction of black holes will mate with low mass stars, we could scientifically infer the population of isolated black holes out there.”

Based on the data from Chandra X-ray Observatory, the team tested the technique and searched for X-ray signatures indicating the fusion between a black hole and a low mass binary in an inactive state. Within three light years of the supermassive black hole, they found 12 black holes-low mass binaries.

The spatial distribution of the emissions they tracked indicates that there are about 300 to 500 black hole and low mass binaries and approximately 10,000 black holes in the area close to the Sagittarius A.

Discovering the existence of these 10,000 black holes surrounding the supermassive black hole Sagittarius A will be a valuable tool in the advancement of gravitation wave research and other studies involving the universe.
New strong evidence supporting the existence of an intermediate-mass black hole is announced.