Indians in team spotting most massive black hole merger

A team of Indian astronomers and a specialised computing facility created at an institute in Pune played a key role in detecting the most massive merger of two black holes ever observed more than seven billion years ago.

The collision between the two black holes led to the creation of an “intermediate-mass black hole”.

Read: LIGO, Virgo Capture their most massive black holes yet

The two black holes that collided have 85 and 66 times the mass of the Sun, forming a bigger black hole of mass 142 times that of the Sun.

Black holes are remnants of massive dying stars, with gravity so monstrous that even light can’t escape their pull, making them literally black.

This is the first conclusive discovery of an intermediate-mass black hole. This event, its energy detected on Earth in the form of gravitational waves, is the most massive black hole merger yet observed.

An international team of researchers, including several Indian scientists, witnessed the birth of this intermediate-mass black hole by analysing its signature – a feeble gravity wave, labelled GW190521, on May 21, 2019.

They witnessed this with the Laser Interferometer Gravitational-wave Observatory (LIGO), a pair of identical 4-km-long L-shaped instruments in the USA and Virgo - a similar 3-km-long detector in Italy. The signal lasted only about a tenth of a second, but long enough to extract key data.

“Such black holes provide clues to the formation of supermassive black holes, at the core of the galaxies. Since the signal was very short, it could have been mistaken as noisy transient. We look for common signatures in both the detectors to zero in on the merge,” Archana Pai, professor at IIT, Bombay, and part of the team that made the discovery, told DH.

Between the stellar black holes that can be seen with existing detectors and supermassive black holes, there was no candidate for an intermediate range till this discovery.

“Evidences of intermediate mass black holes can complete our understanding of the universe,” said Sanjit Mitra, another team member at the Inter-University Centre for Astronomy and Astrophysics, Pune, which has set up a special high performance computing centre for data analysis.

After LIGO and Virgo, a third gravity detector would be set up in Maharashtra (LIGO India) to detect more such gravity waves that would unravel such unknowns of the universe, commented Tarun Sourdeep, a professor at the Indian Institute of Science, Education and Research, Pune and the spokesperson of the LIGO India project.

The discovery has been published on Wednesday in two papers that appeared in Physical Review Letters and Astrophysical Journal Letters.