Indian astronomers discovers binary super-massive black holes

Two Indian astronomers and their US collaborator on Monday reported the discovery of the closest ever binary super-massive black hole system in a spiral galaxy located about 400 million light-years from the Earth.
 
A black hole is the terminal phase of some of the extremely massive stars, which become so heavy and dense that even light – the fastest runner in the universe – can't escape their gravitational pull, making them literally black.
 
Black holes are amongst most fascinating objects in astronomy and even more the binary systems in which two black holes orbiting around each other. Scientists still know little about these cosmic monsters that are shrouded in multiple layers of mysteries.
 
What Preeti Kharab and Dharam Vir Lal at the National Centre for Radio Astronomy, Pune and David Merritt from the Rochester Institute of Technology, the USA discovered is a pair of black holes, orbiting each other in extremely close proximity.
 
The duo is separated by a distance of less than one light year (the distance travelled by the light in a year or 5.9 trillion miles). In astronomical terms, one light year is a small distance.
 
“This discovery is very significant because this is a direct observational proof of the existence of close super-massive black hole binary systems inside galaxies that are potential sources of gravitational waves,” Lal told DH. The findings have been reported in the journal Nature Astronomy on Monday.
 
The combined mass of the two black holes is roughly forty million times the mass of the Sun. The scientists estimated the orbital period of the binary to be about one hundred thousand years.
 
The new system in the gas-rich spiral galaxy named NGC 7674 has much lesser separation distance compared to the only other known binary black hole system where two such cosmic giants are separated by a distance of 24 light years.
 
Astrophysicists have long predicted the existence of a class of binaries, consisting of super-massive black holes, each having a mass upwards of one million times the mass of the Sun.
 
Single super-massive black holes are known to be present at the centres of most galaxies, and since galaxies are observed to merge with other galaxies, it is possible to form gravitationally bound black hole pairs. In due course of time, these two super-massive black holes would coalesce via the emission of gravitational waves.
 
The existence of binary black holes, roughly ten times the mass of Sun, was confirmed by the 2015 discovery of the gravitational waves by LIGO telescope.
 
For the binary black hole discovery, the Indo-US team used data generated by the Very Long Baseline Array – a radio telescope located in New Mexico, USA.