Researchers discover new monster black hole ‘practically in our back yard’

The discovery of a so-called monster black hole about 12 times the mass of the sun is detailed in a new Astrophysical Journalresearch submission, whose lead author Dr. Sukanya Chakrabarti is a physics professor at the University of Alabama at Huntsville (UAH).

“It is closer to the Sun than any other known black hole, at a distance of 1,550 light-years,” said Dr. Chakrabarti, the Pei-Ling Chan Endowed Chair in the Department of Physics at the University of Alabama, UAH. System. “So it’s practically in our backyard.”

Black holes are considered exotic because although their gravity is clearly felt by stars and other objects in their environment, no light can escape a black hole, so they cannot be seen in the same way as visible stars.

“In some cases, such as supermassive black holes at the centers of galaxies, they can stimulate the formation and evolution of galaxies,” said Dr. Chakrabarti.

“It is not yet clear how these non-interacting black holes affect the galactic dynamics in the Milky Way. If they are numerous, they could influence the formation of our galaxy and its internal dynamics.”

To find the black hole, Dr. Chakrabarti and a national team of scientists provided data from nearly 200,000 binary stars released over the summer by the European Space Agency’s Gaia satellite mission.

“We looked for objects that were reported to have large companion masses, but whose brightness can be attributed to a single visible star,” she says. “So you have good reason to think the companion is dark.”

Interesting sources were followed up with spectrographic measurements from several telescopes, including the Automated Planet Finder in California, the Chilean Giant Magellan Telescope and the WM Keck Observatory in Hawaii.

“The gravitational pull of the black hole on the visible Sun-like star can be determined from these spectroscopic measurements, which give us a line-of-sight velocity due to a Doppler shift,” said Dr. Chakrabarti. A Doppler shift is the change in frequency of a wave relative to an observer, such as how the pitch of a siren’s sound changes as an emergency vehicle passes.

“By analyzing the line-of-sight velocities of the visible star — and this visible star is related to our own sun — we can deduce how massive the black hole’s companion is, as well as its rotation period and how eccentric its orbit is,” she says. “These spectroscopic measurements independently confirmed the Gaia solution which also indicated that this binary system is composed of a visible star orbiting a very massive object.”

The black hole must be inferred from analyzing the movements of the visible star because it does not interact with the luminous star. Non-interacting black holes usually do not have a donut-shaped ring of accretion material and material that accompanies black holes interacting with another object. Accretion makes the interacting type relatively easier to observe optically, which is why many more of that type have been found.

“Most black holes in binary systems are in X-ray binaries — in other words, they are bright in X-rays because of some interaction with the black hole, often because the black hole is devouring the other star,” said Dr. Chakrabarti. “As the stuff from the other star falls down into this deep gravitational potential, we can see X-rays.”

These interacting systems are usually in short-period orbits, she says. “In this case, we’re looking at a monstrous black hole, but it’s in a long orbit of 185 days, or about half a year,” said Dr. Chakrabarti. “It’s quite far from the visible star and isn’t making any headway toward it.”

The techniques the scientists used should also be applied to find other non-interacting systems.

“This is a new population that we’re just starting to learn about that will tell us about the black hole formation channel, so it’s been really exciting to work on this,” said Peter Craig, a doctoral student at the Rochester Institute of Technology who is working on this. his dissertation is advised by Dr. Chakrabarti.

“Simple estimates suggest that there are about a million visible stars that have massive black hole companions in our galaxy,” said Dr. Chakrabarti. “But there are a hundred billion stars in our galaxy, so it’s like looking for a needle in a haystack. The Gaia mission, with its incredibly accurate measurements, made it easier by refining our search.”

Scientists are trying to understand the formation pathways of non-interacting black holes.

“There are currently several pathways proposed by theorists, but non-interacting black holes around luminescent stars are a whole new type of population,” said Dr. Chakrabarti. “So, it will probably take us some time to understand their demographics, and how they form, and how these channels are different — or similar — to the more familiar population of interacting, merging black holes.”