The Laser Interferometer Gravitational-wave Observatory (LIGO) said today that it had made another successful detection of gravitational waves, ripples in space and time, from the merger of two massive black holes that happened three billion light years away.
The new detection occurred on January 4 this year during the ongoing second observing run of the Advanced LIGO detectors in the US, which began on November 30, 2016.
The third event was produced by the merger of two black holes, 31 and 19 times as massive as the Sun, forming a larger black hole of about 49 solar masses.
Also, data suggests that at least one of the black holes in this binary system might have been spinning in a direction that is not completely aligned with the orbital rotation of the binary, providing potential clues on how these binaries might have formed.
"The new event also provides new opportunities to test Einstein's theory of general relativity.
"For example, this allowed us to confirm Einstein's prediction that gravitational waves should not undergo dispersion -- the phenomena of waves travelling at different speeds depending on their wavelength. Indian scientists played a leading role in deriving this result," said Sanjit Mitra from the Pune-based Inter-University Centre for Astronomy and Astrophysics (IUCAA), researchers of which have participated in the LIGO discoveries.
Mitra, Anirban Ain, Sukanta Bose, Sanjeev Dhurandhar, Bhooshan U Gadre, Sharad G Gaonkar, Nikhil Mukund, Jayanti Prasad and Tarun Souradeep --- all from IUCAA -- were part of the team.
Sixty-seven scientists from 13 Indian institutions are part of the LIGO Scientific Collaboration, under the umbrella of the Indian Initiative in Gravitational-Wave Observations (IndIGO).
The Indian team in LIGO includes scientists from CMI Chennai, ICTS-TIFR Bengaluru, IISER-Kolkata, IISER-Trivandrum, IIT-Bombay, IIT-Madras, IIT-Gandhinagar, IIT-Hyderabad, IPR Gandhinagar, IUCAA Pune, RRCAT Indore, TIFR Mumbai and UAIR Gandhinagar.
Indian scientists have done foundational work over the last three decades in modelling the signal waveforms and developing mathematical techniques to search for gravitational wave signals in noisy data.
A new generation of Indian scientists are expanding these contributions on several other frontiers. The publication has 40 authors from 11 Indian institutions.
The first direct observation of gravitational waves was made in September 2015 during the first observing run. A second detection was made in December 2015.
These detections were made possible by contributions from more than thousand researchers from many different countries, setting a great example in collaborative science.
There are only two LIGO laboratories in the world, both located in the US. The third laboratory is to come up in Hingoli district in Maharashtra.
Describing the achievements to be really satisfying, IUCAA Director Somak Raychaudhury said, "The continuing discoveries of GW events as expected shows how this subject is rapidly evolving into a distinct field of Science. I am proud that scientists in India, in particular at IUCAA, continue to play leading roles."
