In recent news, a unique astronomical phenomenon was brought into focus. A compact binary merger created a long Gamma Ray Burst (GRB), which was accompanied by kilonova emissions. This peculiar pairing of phenomena has never before been scientifically validated or proven. This event was corroborated by India’s most significant optical telescope, the Devasthal Optical Telescope (DOT).
The series of events included a GRB that lasted over 50 seconds, identified as GRB211211A. Kilonovae were identified as the result of two compact bodies, such as binary neutron stars or a neutron star and a black hole, colliding.
Understanding Gamma-Ray Bursts (GRBs)
GRBs are massive but intensely bright, high-energy short gamma radiations, released when colossal stars in the universe collapse or die. As some of the most potent occurrences in the universe, they are detectable across billions of light-years. To contextualize, a light-year is the distance that a light beam traverses in a single Earth year, equivalent to 9.5 trillion kilometers.
Depending on whether the event lasts for more than two seconds or less, astronomers categorize them as either long or short GRBs.
Long GRBs and their association with Stellar Demise
Long GRBs have often been observed in relation to the demise of colossal stars. When a star, significantly larger than the sun, depletes its fuel, its core suddenly collapses, forming a black hole. A black hole is a region in space where matter is so intensely compressed that it creates a gravity field so strong that even light cannot escape.
As matter spirals into the black hole, some of it escapes in the form of two potent jets that rush outwards at nearly the speed of light in opposite directions. Only when one of these jets points almost directly towards Earth is a GRB detected. Each jet pierces through the star, producing a gamma ray pulse – the highest-energy form of light – that lasts up to minutes. The star, post-disruption, expands rapidly as a supernova- an exploding star that signifies the end of its life.
Short GRBs and the Collision of Compact Objects
In contrast, a short GRB forms when pairs of compact objects – such as neutron stars formed during stellar collapse – spiral inward over billions of years and collide. A neutron star comprises one of the possible evolutionary end-points of high mass stars.
Significance of Observing Blackhole Mergers
In previous years, scientists have observed the merger of giant blackholes billions of light-years away from Earth. As per a question in the UPSC Civil Services examination, the significance of this observation primarily includes the detection of ‘Gravitational Waves,’ which further reinforces our understanding of the cosmos.