Gravitational waves from merged black holes
doi:10.1038/nindia.2017.70 Published online 20 June 2017
Astrophysicists have detected signals of gravitational waves emanating from a merger of two massive black holes, located three billion light years away1. Travelling at the speed of light, gravitational waves carry information about their cataclysmic origins, as well as invaluable clues on the nature of gravity and the evolution of the Universe.
Colliding black holes emit little or no electromagnetic radiation, but they shine brightly while emitting gravitational waves.
To detect gravitational wave signals, an international research team of scientists from the Tata Institute of Fundamental Research, Mumbai, Chennai Mathematical Institute, Chennai, Inter-University Centre for Astronomy and Astrophysics, Pune and Indian Institute of Technology, Madras analysed the data of twin detectors at the US-based Laser Interferometer Gravitational-wave Observatory (LIGO).
Sophisticated instruments recorded a gravitational-wave “chirp” from the merger of two black holes whose combined mass is 50 times that of the Sun. The observations also give insight into the typical properties of binary black holes, including their spins.
Analysis shows that this is the third merger of black holes, the first and second happened 1.3 and 1.4 billion light years away, respectively.
The study didn’t find any evidence for dispersion, a phenomenon which occurs when light waves travel in a physical medium such as glass. This supports Einstein's general theory of relativity which forbids dispersion in gravitational waves as they propagate from their source to Earth.
1. Abott, B. P. et al. GW170104: observation of a 50-solar-mass binary black hole coalescence at redshift 0.2. Phys. Rev. Lett. 118, 221101 (2017)