India's contribution behind discovery of the heaviest black hole merger

New Delhi: An algorithm created by Indian researchers and two critical analyses by astrophysicists in Mumbai and Kozhikode were instrumental in a major international scientific discovery announced on Monday - the most massive black hole collision known till date.

A network of gravitational wave observatories in the USA and Europe picked up the signals emanating from the merger of two black holes with masses 137 and 103 times the mass of the sun, producing a black hole 240 times the mass of the sun.

Even though the discovery of the gravitational wave signal GW231123 – announced at a conference in Glasgow - is the outcome of a multi-institution collaboration, several Indian research groups played critical roles in analysing the data.

“One of the algorithms used for the analysis was developed by us. A young researcher from IIT Bombay made a deep specific analysis, vital to the discovery. Another group at the National Institute of Technology, Calicut also made a critical contribution,” Archana Pai from Indian Institute of Technology, Bombay and one of India’s leading gravitational wave scientists told DH.

Black holes are heavy-weight stars in the death bed with such a huge gravity that even light – the fastest runner in the universe – can’t escape them, making them black. A majority of the known black holes are in the range of 5 – 30 solar mass.

For the first time, the researchers observed the merger of two black holes with colossal 103 and 137 times the masses of the sun, thanks to the gravitational wave detectors.

In addition to being extremely massive, the two black holes are spinning incredibly fast, making this a uniquely challenging signal to interpret and suggesting the possibility of a complex formation history.

“Black holes this massive are forbidden within our current understanding of the formation of these objects from the evolution of massive stars. One possibility is that the two black holes in this binary formed through earlier mergers of smaller black holes," said Mark Hannam, from Cardiff University and a member of the team.

Pai said the merged black hole is at a distance of nearly 10 billion light years away from the earth and provided clues on how such massive cosmic bodies are formed by fusing two smaller ones.

The signal, just a tenth of a second long, was a puzzle at first, but the scientists soon realised that it matched the signature of merging black holes, just as Einstein’s general relativity predicts.

“We realised that we may have, for the first time, witnessed the collision of two intermediate-mass black holes. But uncovering its true origin and extracting all the science out of it will take years,” said Koustav Chandra, a scholar from IIT Bombay, who contributed significantly to analyzing and interpreting the GW231123 data.

M K Haris at the NIT, Calicut said his group checked if the data was consistent with the General Theory of Relativity. “This is the heaviest event observed since 2015, suggesting the formation of black holes from channels beyond standard stellar collapse,” he said.

India is in the process of setting up a Rs 2,600 crore gravitational wave observatory at Hingoli in Maharashtra. Once ready, it will join the global network of such detectors in the USA, Europe and Japan.