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Indian astronomers have found an active galaxy in a very bright state with 10 times more X-ray emission than normal, equivalent to more than 10 trillion of the sun, and located five billion light years away that could help probe how particles behave under intense gravity and acceleration to the speed of light.
It could help study the role of strong gravity and acceleration of matter in the formation, interaction and evolution of galaxies in the early universe.
Every galaxy in the universe is believed to host a supermassive black hole at its centre. In some galaxies, the black hole is actively devouring a large amount of material and shooting a jet of plasma almost at the speed of light towards us. These are called blazars.
OJ 287 belongs to a class of blazars known as BL Lacertae objects which show very rapid and large amplitude flux variations but barely discernible emission line features.
This class of sources emit in the whole electromagnetic spectrum, a rather uncommon phenomenon which requires extreme physical conditions. Hence, a study of such sources tells us about the behaviour of matter in an extreme gravitational field where it is difficult for light to escape from the vicinity of the black hole.
Astronomers at Aryabhatta Research Institute of Observational Sciences, an autonomous institute of the Department of Science and Technology, Government of India, have been monitoring one such black hole system named 'OJ 287' since 2015. This source shows a repeated optical brightness enhancement almost every 12 years.
"The repeated optical enhancement makes OJ 287 very intriguing as this class of sources does not show any repeating features in flux variations. The repeated optical enhancement made the researchers believe that the system hosts a binary black hole," said a release from the Ministry of Science and Technology.
In 2020, the source was very bright at optical and X-ray bands with X-ray flux more than 10 times the normal (non-active phase) flux. This flare was very different as it was not expected in models proposed for this source and thus, indicated a more complex system and physical conditions.
Investigating the extreme brightness shown by OJ 287 at optical and X-ray bands, astronomers led by Pankaj Kushwaha and Alok C. Gupta reported the source in a completely new spectral state.
The team argued that this change of state holds clues to the researcher's quest to understand how matter behaves in very strong gravity and how it accelerates the particle to almost the speed of light -- a feat that is out of the scope of even the most advanced CERN accelerator.
The research published in 'The Astrophysical Journal' tracked the details of changes in optical to the X-ray emission spectrum of the source with time from 2017 to 2020 -- after the second brightest X-ray flare of the source. It revealed how the source gradually started to change its spectral behaviour from mid-2018 to the new spectral state in 2020.
The study included data recorded by the ground-based facility operated by Physical Research Laboratory, Ahmedabad, operated Mount Abu observing facility in near infra-red bands and the space-based NASA's satellites -- the Niels Gherel Swift satellite at optical, UV and X-rays with gamma ray data from the Fermi satellite, the release added. (IANS/JB)
Keywords: Science, NASA, Satellites, Black Hole, Gravity, India
Astronomers have discovered a small black hole outside the Milky Way by looking at how it influences the motion of a star in its close vicinity.
The team at Liverpool John Moores University in the UK used the European Southern Observatory's Very Large Telescope (ESO's VLT), situated in the Atacama Desert of northern Chile, to spot the black hole.
The newly found black hole was spotted lurking in NGC 1850, a cluster of thousands of stars roughly 160,000 light years away in the Large Magellanic Cloud -- a neighbour galaxy of the Milky Way. The detection in NGC 1850 marks the first time a black hole has been found in a young cluster of stars (the cluster is only around 100 million years old, a blink of an eye on astronomical scales).
According to Sara Saracino from the Liverpool John Moores University's Astrophysics Research Institute, the black hole is roughly 11 times as massive as our Sun. Astronomers started on the trail of this black hole due to its gravitational influence on the five-solar-mass star orbiting it.
Previously such small, "stellar-mass" black holes have been spotted in other galaxies by picking up the X-ray glow emitted as they swallow matter, or from the gravitational waves generated as black holes collide with one another or with neutron stars.
However, most stellar-mass black holes don't give away their presence through X-rays or gravitational waves.
This is the first time this detection method has been used to reveal the presence of a black hole outside of our galaxy. The method could be key to unveiling hidden black holes in the Milky Way and nearby galaxies, and to help shed light on how these mysterious objects form and evolve, the team said.
"Every single detection we make will be important for our future understanding of stellar clusters and the black holes in them," said co-author Mark Gieles from the University of Barcelona, Spain. (IANS/JB)
Keywords: Black Hole, Space, Milky Way Galaxy, Science, Technology.
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Fifty years after physicist Stephen Hawking derived the black hole theorem, physicists at the Massachusetts Institute of Technology have confirmed it for the first time, using observations of gravitational waves.
In 1971, Hawking proposed the area theorem, which set off a series of fundamental insights about black hole mechanics. The theorem predicts that the total area of a black hole's event horizon -- and all black holes in the universe, for that matter -- should never decrease. The statement was a curious parallel of the second law of thermodynamics, which states that the entropy, or degree of disorder within an object, should also never decrease.
In the study, which appears in the Physical Review Letters, the researchers took a closer look at GW150914, the first gravitational wave signal detected by the Laser Interferometer Gravitational-wave Observatory (LIGO), in 2015. The signal was a product of two in-spiraling black holes that generated a new black hole, along with a huge amount of energy that rippled across space-time as gravitational waves.
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If Hawking's area theorem holds, then the horizon area of the new black hole should not be smaller than the total horizon area of its parent black holes.
The MIT physicists team reanalyzed the signal from GW150914 before and after the cosmic collision and found that indeed, the total event horizon area did not decrease after the merger -- a result that they report with 95 percent confidence.
A black hole devours a neutron star. Wikimedia Commons
Their findings mark the first direct observational confirmation of Hawking's area theorem, which has been proven mathematically but never observed in nature until now. The team plans to test future gravitational wave signals to see if they might further confirm Hawking's theorem or be a sign of new, law-bending physics.
"There may be a zoo of different compact objects, and while some of them are the black holes that follow Einstein and Hawking's laws, others may be slightly different beasts," said lead author Maximiliano Isi, from MIT's Kavli Institute for Astrophysics and Space Research.
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"So, it's not like you do this test once and it's over. You do this once, and it's the beginning," Isi added.
The similarity between the two theories suggested that black holes could behave as thermal, heat-emitting objects -- a confounding proposition, like black holes by their very nature, were thought to never let energy escape, or radiate. Hawking and others have since shown that the area theorem works out mathematically, but there had been no way to check it against nature until LIGO's first detection of gravitational waves.
The team plans to further test Hawking's area theorem, and other longstanding theories of black hole mechanics, using data from LIGO and Virgo, its counterpart in Italy. (IANS/KB)
Peering back 10 billion years into the universe’s past, astronomers have found a pair of quasars that are so close to each other they look like a single object in ground-based telescopic photos, but not in the Hubble Space Telescope’s crisp view. The researchers believe the quasars are very close to each other because they reside in the cores of two merging galaxies. The team went on to discover yet another quasar pair in another colliding galaxy duo.
A quasar is a brilliant beacon of intense light from the center of a distant galaxy that can outshine the entire galaxy. It is powered by a supermassive black hole voraciously feeding on inflating matter, unleashing a torrent of radiation.
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“We estimate that in the distant universe, for every 1,000 quasars, there is one double quasar. So finding these double quasars is like finding a needle in a haystack,” said lead researcher Yue Shen of the University of Illinois at Urbana-Champaign in the US.
The discovery of these four quasars offers a new way to probe collisions among galaxies and the merging of supermassive black holes in the early universe, researchers said. Quasars are scattered all across the sky and were most abundant 10 billion years ago. There were a lot of galaxy mergers back then feeding the black holes. Therefore, astronomers theorize there should have been many dual quasars during that time.
“This truly is the first sample of dual quasars at the peak epoch of galaxy formation with which we can use to probe ideas about how supermassive black holes come together to eventually form a binary,” said research team member Nadia Zakamska of the Johns Hopkins University in Baltimore, Maryland. The team’s results appeared in the online issue of the journal Nature Astronomy.
Shen and Zakamska are members of a team that is using NASA’s Hubble Space Telescope, the European Space Agency’s Gaia space observatory, and the Sloan Digital Sky Survey, as well as several ground-based telescopes, to compile a robust census of quasar pairs in the early universe. The observations are important because a quasar’s role in galactic encounters plays a critical part in galaxy formation, the researchers said. (IANSSP)