Scientists find mysterious tiny black hole in the Milky Way which could be smallest in the universe
Scientists developed a different approach to detect black holes of small mass by examining how a companion star moves in response to its gravity
In their decades-long hunt for black holes, astronomers may have overlooked a whole class of these celestial mysteries, suggests a new study. The never-seen-before black hole may be smaller than the smallest known black hole in the universe.
A black hole can be as large as 31 times the mass of the sun. But the black hole the scientists found is likely to be 3.3 times the mass of the sun and way larger than neutron stars, according to Todd Thompson, the author of the study and a professor of astronomy at the Ohio State University.
Most earlier methods used X-rays to detect black holes in our Milky Way, Thompson told MEA WorldWide (MEAWW). This method builds on the interaction between a black hole and an accompanying star. He explains that the accompanying star siphons off gas to the black hole. This causes the gas to get heated and release X-rays.
This method allowed scientists to detect black holes of large masses. Thompson and other astrophysicists had long suspected that black holes might come in sizes outside the known range, they knew that black holes could be large. The team was interested in finding out whether black holes could exist in sizes between the biggest neutron stars and the smallest black holes.
Imagine a census of a city that only counted people 5'9" and taller - and imagine that the census takers didn't even know that people shorter than 5'9" existed. Data from that census would be incomplete, providing an inaccurate picture of the population. That is essentially what has been happening in the search for black holes, he explains
So the team could not adopt the X-ray method. "In our case, the companion [star] is dark, with no X-ray emission," says Thompson.
As a result, the scientists developed a different approach to detect black holes of small mass. They examined how the companion star moves in response to the gravitational pull of the black hole.
By going through a huge chunk of data, they found that giant red star appeared to be orbiting something, which according to their calculations, was smaller than the known black holes in the Milky Way, but way bigger than most known neutron stars.
After more calculations and additional data from the Tillinghast Reflector Echelle Spectrograph and the Gaia satellite, they realized they had found a low-mass black hole, likely about 3.3 times the mass of the sun.
"This might be the first system with a black hole in the “mass gap” between the most massive neutron stars and the lowest mass black hole," Thompson told MEAWW.
The study, Thompson says, could explain why some stars collapse to form neutron stars and supernova explosions while others collapse to black holes. "We are very interested in the success or failure of massive star core collapses over time because these systems enrich the universe with the elements of existence," Thompson told MEAWW.