An Indian space telescope has helped astrophysicists to capture the signal of a black hole birth. The telescope has now detected 500 signals of black hole formation.
Black holes are born when massive stars die through violent explosions. As they collapse, the stars produce gamma-ray bursts (GRBs). The telescope, called AstroSat, detects GRBs that emit streams of highly energetic photons. These photons travel at the speed of light and spread across space and head towards Earth.
The researchers say the study of gamma-rays from such bursts will help scientists better understand what happens when black holes form from the death of massive stars.
GRBs can last anything from a fraction of a second to over 1,000 seconds, making it difficult for telescopes to detect them. AstroSat overcomes this by using Cadmium Zinc Telluride Imager (CZTI), a sensitive photon-counting detector that records the time of arrival, energy and position of each photon. The telescope can simultaneously study cosmic events at ultraviolet, visible and x-ray wavelengths.
Since its launch in September 2015, the AstroSat CZTI has detected 500 GRB signals with an average of 75 GRBs every year.
“CZTI can measure X-ray polarisation of GRBs that tells us what is happening just outside a newly formed black hole,” says Varun Bhalerao, an astrophysicist at the Indian Institute of Technology Bombay in Mumbai. He leads the GRB search with researchers at the Inter-University Centre for Astronomy and Astrophysics in Pune and the Tata Institute of Fundamental Research in Mumbai.