Black holes are among the most amazing and mysterious things in the known universe. These giant gravitational planets form when massive stars undergo gravitational collapse at the end of their lives and shed their outer layers in a supernova explosion.
Meanwhile, the stellar remnant becomes so dense that the curvature of spacetime becomes infinite in its vicinity and its gravity is so intense that nothing (not even light) can escape its surface. This makes them impossible to observe with conventional optical telescopes that study objects in visible light.
As a result, astronomers usually look for black holes with invisible wavelengths or by observing their effect on objects in their vicinity.
After consulting the Gaia Data Release 3 (DR3), a team of astronomers led by the University of Alabama Huntsville (UAH) recently observed a black hole in the cosmic backyard. As they describe in their study, this monstrous black hole is roughly twelve times the mass of our sun and is located about 1,550 light-years from Earth.
Due to its mass and relative proximity, this black hole provides opportunities for astrophysicists.
The study was led by Dr Sukanya Chakrabarti, chair of Pei-Ling Chan Endowed in the Department of Physics at UAH. It was joined by astronomers from the observatories of the Carnegie Institution for Science, the Rochester Institute of Technology, the SETI Institute, the Carl Sagan Center, the University of California, Santa Cruz, the University of California at Berkeley, the University of Notre Dame, Wisconsin-Milwaukee, Hawaii, and Yale.
The paper describing their findings recently appeared online and is being reviewed by Astrophysical Journal.
Black holes are of particular interest to astronomers because they provide opportunities to study the laws of physics under the most extreme conditions. In some cases, such as Supermassive Black Holes (SMBH) located at the center of most massive galaxies, they also play a vital role in the formation and evolution of galaxies.
However, there are still unresolved questions regarding the role that non-interacting black holes play in the evolution of galaxies. These binary systems consist of a black hole and a star, in which the black hole does not pull material from its companion star. Dr. Chakrabari said in a UAH press release:
“It is not yet clear how these non-interacting black holes affect galactic dynamics in the Milky Way. If they are numerous, they may affect the composition and internal dynamics of our galaxy. We searched for objects to which large companion masses have been reported but can be attributed Its brightness is reduced to one visible star. Thus, you have good reason to believe that your companion is dark.”
To find the black hole, Dr. Chakrabarti and her team analyzed data from Gaia DR3, which included information on nearly 200,000 binary stars observed by ESA’s Gaia Observatory. The team pursued sources of interest by consulting spectroscopic measurements from other telescopes, such as the Lick Observatory’s Automated Planet Finder, the Giant Magellan Telescope (GMT), and the WM Keck Observatory in Hawaii.
These measurements showed a main sequence star subject to a strong gravitational force. As Dr. Chakrabari explained:
“The black hole’s pull on the visible sun-like star can be determined by these spectroscopic measurements, which give us the line-of-sight velocity due to the Doppler shift. By analyzing the line-of-sight velocities of the visible star – and this visible star is similar to our sun – we can infer how massive the black hole’s companion is, as well as to the rotation period, and the extent of the orbit skew. These spectroscopic measurements independently confirmed the Gaia solution which also indicated that this binary system consists of a visible star orbiting an extremely massive object.”
The interaction of black holes in visible light is usually easier to see because they are in tighter orbits and pull material from their stellar companions. This material forms a torus-shaped accretion disk around the black hole that is accelerated to relativistic velocities (close to the speed of light), becoming high-energy and emitting X-rays.
Since non-interacting black holes have wider orbits and do not form these disks, their existence must be inferred from the analysis of the motions of the visible star. Dr. Chakrabarti said:
“The majority of black holes in binary systems are in X-ray binaries – in other words, they are bright in X-rays due to some interaction with the black hole, often due to the black hole devouring the other star. From the other star this deep gravitational effort falls well, we can see the rays X-rays. In this case, we’re looking at a monster black hole, but it’s in a long orbit of 185 days, or about half a year. It’s too far from the visible star and making no progress toward it.”
The techniques used by Dr. Chakrabarti and her colleagues could lead to the discovery of many non-interactive systems.
According to current estimates, there could be a million visible stars in our galaxy that have massive black hole companions. While this is a small fraction of the number of stars (about 100 billion), accurate measurements by Gaia Observatory have narrowed this search. So far, Gaia has obtained data on the appropriate locations and motions of more than a billion astronomical objects – including stars and galaxies,
Additional studies of this group will allow astronomers to learn more about this group of binary systems and the path of formation of black holes. As Dr. Chakrabarti summarized:
“There are currently many different approaches that theorists have proposed, but non-interacting black holes around luminaries are a very new type of population. So, it will likely take some time to understand their demographics, how they form, and how these channels differ—or If they are the same – about the groups most famous for interaction, merging black holes.”
This article was originally published by Universe Today. Read the original article.
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