The recent scientific advancements have brought to light the intriguing insights into the universe’s enigmatic entities – black holes. A team of researchers from the Chennai Mathematical Institute and other associated institutions have conducted an in-depth analysis of the data gathered from the LIGO-VIRGO observatories. The primary objective of these observations is to estimate the fraction of binary Black Hole mergers detected so far, which show promising potential for the formation of Intermediate-Mass Black Holes.
Understanding Black Hole Mergers
Black Hole mergers are a cosmic phenomenon involving the amalgamation of two or more black holes. Indian scientists have managed to observe the merger of three supermassive black holes previously. The resulting product of these mergers varies, leading to the creation of different types of black holes such as Intermediate-Mass Black Holes and Binary Black Holes.
Intermediate-Mass Black Holes (IMBHs)
Intermediate-Mass Black Holes present themselves as a distinct category of black holes, carrying mass within the range of 102-105 solar masses. This range situates them between the lighter stellar black holes and the heavier supermassive black holes. One prevalent theory regarding the formation of IMBHs involves ‘hierarchical growth’. As per this theory, if black holes exist within a dense cluster of stars, the remnant (black hole) of a merger can pair up with another nearby black hole to form a binary. These binaries can eventually merge to form a second, more massive remnant, thereby explaining the process behind the formation of intermediate-mass black holes.
The Role of Gravitational Waves in Black Hole Mergers
The phenomenon of two black holes orbiting each other and merging gives rise to Gravitational Waves (GW). These waves carry significant implications for understanding another essential aspect of black hole mergers – the ‘kicks’.
Mergers and “Kicks”
‘Kicks’ refer to the opposing momentum gained by a remnant black hole during mergers. It is a reaction to Gravitational Waves taking away energy and linear momentum during mergers. These kicks can measure large, providing the remnant with a velocity of up to 1000 kilometres per second. If this kick velocity exceeds the cluster’s escape velocity in which the black hole forms, it escapes from its environment and moves out, impeding further hierarchical mergers. Scientists can estimate the extent of the kick received by the remnant, and this estimation helps to identify which mergers could potentially form Intermediate-Mass Black Holes.
Black Hole Origin: From Theory to Observation
A black hole is a highly compressed point in space that creates a gravity field so intense that even light cannot escape from it. Albert Einstein first theorized this concept in 1915, but the term ‘black hole’ was introduced by John Archibald Wheeler.
Black holes originate when a massive star undergoes a supernova explosion towards the end of its lifetime. The remnants of this explosion culminate into the formation of a black hole. However, not all stars are destined to become black holes. Most of them inflate, lose mass, and cool down to form white dwarfs as they reach their life’s end. The larger ones, at least 10 to 20 times as massive as our sun, either transform into super-dense neutron stars or stellar-mass black holes.
Black holes usually fall into two categories: Stellar black holes, with mass ranging from a few to tens of solar masses, are thought to form when massive stars die. On the other hand, supermassive black holes, hundreds of thousands to billions times the Sun’s mass, result from the merger of two or more black holes. In April 2019, a major breakthrough was achieved when scientists from the Event Horizon Telescope Project released the first-ever image of a black hole, or more precisely, its shadow.
