Have astronomers found the 'missing link' of black hole evolution?

But researchers are divided over whether these are really midsized black holes, shining bright as they imbibe lots of surrounding gas, or smaller ones ingesting at a superfast rate. The largest, supermassive black holes, lurk at the center of galaxies, while small black holes result from the collapse of huge stars.

Artistic representation of a black hole.

But astronomers also know that much larger, supermassive black holes lie at the heart of large galaxies including the Milky Way, where Sagittarius A* weighs as much as 400m suns. The black hole appears to be mid-sized and not almost as big as the giant ones present at the centers of galaxies. Meaning, as soon as the black hole is formed, the matter from the companion star is sucked into itself by the black hole, and eventually, the companion star ceases to exist.

According to Time and Newsweek, those gases (which moved at different speeds and included molecules such as carbon monoxide and hydrogen cyanide) appeared to be moved by powerful gravitational forces.

Data gathered using the Atacama Large Millimeter Array, or ALMA telescope, revealed that the molecules in the elliptical cloud, which spans 150 trillion kilometers wide, were being pulled around by enormous gravitational forces.

Finding an IMBH would open up a new avenue of research in understanding supermassive black holes-black holes that can be billions of times the mass of the sun that sit at the center of most massive galaxies, including the Milky Way.

Now, Tomoharu Oka and colleagues at Keio University have studied a "peculiar molecular cloud" located near the centre of the Milky Way and concluded that it harbours a black hole weighing in at about 100,000 solar masses - putting it at the more massive end of the IMBH classification.

Writing in Nature Astronomy, the team says that the presence of a IMBH is backed up by observations of a compact region of dense gas near the centre of the cloud. To add further evidence, the researchers built a simulation of the gas cloud and its characteristics, particularly the gas velocities, and found that it, too, pointed to a mid-sized black hole.

In the past, astronomers have conjectured that SMBHs are formed by the merger of smaller black holes, which implied the existence of intermediate ones.

Scientists have known for a while that big and small black holes exist. But they can be detected by their influence on nearby objects, for example if the black hole is in a binary pair with a star, or if it is consuming gas which gets heated as it approaches and shines brightly.

According to theories, the Milky Way should be home to about 100 million smaller black holes, but only 60 have been found. These characteristics could be explained by a "gravitational kick" that is caused by "invisible compact object with a mass of about 105 solar masses".

The size of the hole classifies it as an intermediate-mass black hole (IMBH). A typical stellar-class of black hole can be between approximately three and 10 solar masses.

But Oko and his team posit that CO-0.40-0.22 used to be the nucleus of a dwarf galaxy that was slowly drawn into the Milky Way.

Researchers say they will continue to study the intermediate-mass black hole candidate in the hope of confirming its existence.

'This would make a considerable contribution to the progress of modern physics'.

  • Joey Payne