Experts discover method to weigh giant black holes

ASTRONOMERS HAVE discovered a unique way to weigh supermassive black holes at the centres of galaxies.

The method involves measuring the distances between the galaxies that contain them, and indicates supermassive black holes may not be as massive as previously thought. Scientists believe that mysterious, massive dark objects that lurk at the centre of nearly all galaxies are black holes that can be observed with the right equipment.

They can have masses that can exceed a billion suns, according to the study published in Nature Astronomy.

Such supermassive black holes may power quasars, and may halt the formation of stars by releasing copious amounts of energy which heats up and fragments the gas in their host galaxies.

Researchers say they are tiny compared with their host galaxies – the size of a grape compared with the Earth. But despite this, most observations suggest the bigger the galaxy, the bigger the supermassive black hole in it.

According to the astronomers, you would not expect the size of the black hole to know about the size of the galaxy it resides in, but there must be an intimate link between supermassive black hole growth and galaxy evolution.

This has not been proven, and in the study, the international team led by Dr Francesco Shankar of the University of Southampton, with Dr Viola Allevato at the Normale di Pisa and other partners in the US, Germany, Italy and Chile, set out to explain this link.

The masses of supermassive black holes are usually calculated by measuring the velocity of the surrounding stars or gas. Dr Shankar said: “These findings have significant implications for our understanding of the evolution and growth of supermassive black holes.”