Thousands of Black Holes detected in the Center of Milky Way.

Using the data from NASA’s Chandra X-ray Observatory, astronomers have discovered evidence for thousands of black holes located near the center of our Milky Way galaxy.

This black holes consist of stellar-mass black holes, which typically weigh between 5 to 30 times the mass of the Sun. These newly identified black holes were found within three light years, a relatively short distance on cosmic scales  of the supermassive black hole at our Galaxy’s center known as Sagittarius A*.

Theoretical studies of the dynamics of stars in galaxies have indicated that a large population of stellar mass black holes, as many as 20,000 could drift inward over the eons and collect around Sagittarius A*. This recent analysis using Chandra data is the first observational evidence for such a black hole bounty.

A black hole by itself is invisible. However, a black hole or neutron star locked in close orbit with a star will pull gas from its companion [astronomers call these systems “X-ray binaries”]. 

This material falls into a disk and heats up to millions of degrees and produces X-rays before disappearing into the black hole. Some of these X-ray binaries appear as point-like sources in the Chandra image.

A team of researchers, led by Chuck Hailey of Columbia University in New York, used Chandra data to search for X-ray binaries containing black holes that are located near the Sagittarius A*. They studied the X-ray spectra, that is the amount of X-rays seen at different energies of sources within about 12 light years of the supermassive black hole.

The result of the study imply that, at least 300 and up to a thousand containing stellar-mass black holes should be present around Sagittarius A* .

This population of black holes with companion stars near Sagittarius A* could provide insight into the formation of X-ray binaries from close encounters between stars and black holes. 

This discovery could also inform future gravitational wave research. Knowing the number of black holes in the center of a typical galaxy can help in better predicting how many gravitational wave events may be associated with them.

While the authors strongly favor the black hole explanation, they cannot rule out the possibility that up to about half of the observed dozen sources are from a population of millisecond pulsars - very rapidly rotating neutron stars with strong magnetic fields.

Image Credit: NASA/JPL-Caltech
Original Source: Nasa.gov