The existence of the so-called intermediate-mass black holes (IMBH) has been a subject of debate because it is extremely hard to find one. Scientists, however, now have the strongest evidence to date that the elusive black hole exists.

Intermediate-Mass Black Holes

There are two main classes of black holes. The supermassive black holes such as the Sagittarius A* at the center of the Milky Way have a mass equivalent to up to billions of times the mass of the sun. The stellar mass black holes, on the other hand, only have about 10 times the solar mass.

In between these extremes are intermediate-mass black holes, which are thought to be seeds that will later grow to become supermassive black holes. Proof of this class of black holes has been elusive, and very few robust candidates have so far been found.

Hunting For Intermediate-Mass Black Holes

Intermediate-mass black holes are believed to form in various ways, and one of these involves the merger of massive stars in dense star clusters, which makes the center of these stellar clusters a good place to search for this class of black hole.

These black holes, though, tend to become devoid of gas once they have formed. This leaves them with no material to consume, so little radiation is emitted, making them extremely difficult to detect.

The researchers said that one method to find an IMBH is to wait for a star to pass close to it and become disrupted, which will essentially activate the appetite of the black hole and prompt it to emit an observable flare.

Flare Produced By Intermediate-Mass Black Holes Devouring A Star

They were able to observe one candidate by sifting through data collected by ESA's XMM-Newton X-ray space observatory and NASA's Chandra X-Ray Observatory and Swift X-Ray Telescope.

Dacheng Lin of the University of New Hampshire and colleagues detected an enormous flare of radiation in the outskirts of a galaxy about 740 million light-years away. The flare was emitted as a star approached too close to a black hole and was subsequently devoured.

The researchers think that the star was disrupted and torn apart by a black hole with mass equivalent to about 50,000 times that of the sun.

"This thermal-state signature, coupled with very high luminosities, ultrasoft X-ray spectra and the characteristic power-law evolution of the light curve, provides strong evidence that the source contains an intermediate-mass black hole with a mass tens of thousand times that of the solar mass." the researchers wrote in their study, which was published in Nature Astronomy on June 18.