Context: Recently, One of the latest yet extremely rare observations is the merger of two black holes captured by scientists from the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo interferometer in Pisa, Italy

Key Points

• According to the scientists, LIGO is a pair of twin detectors, which are based in Hanford, Washington, and Livingston, Louisiana. 
• The gravitational wave observatories at LIGO scientific collaboration have detected a merger of two unequal-mass black holes. The event has been named as GW190412.
• Event GW190412 took place about 1.9 to 2.9 billion light-years away from Earth and the two black holes weighed approximately 8 and 30 solar masses?
• This is the first such observation involving two black holes of unequal masses coalescing.
• The detected signal’s waveform has special extra features in it when it corresponds to the merger of two unequal-sized black holes as compared to a merger of equal-sized black holes.
• This event has opened new boundaries for further study on black holes, their merger and gravitational waves.

About Black hole

• A black hole is a region of spacetime where gravitational forces are so strong that no particles or even electromagnetic radiation such as light can escape from it.
• The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying.
• The general theory of relativity (GTR) is the geometric theory of gravitation published by Albert Einstein in 1915 and the current description of gravitation in modern physics.
• The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole.

About Gravitational waves

• Gravitational waves are ‘ripples’ in space-time caused by violent and energetic processes in the universe.
• Albert Einstein predicted the existence of gravitational waves in 1916 in his general theory of relativity.
• Einstein’s mathematics showed that massive accelerating objects (such as neutron stars or black holes orbiting each other) would disrupt space-time in such a way that ‘waves’ of undulating space-time would propagate in all directions away from the source. These cosmic ripples would travel at the speed of light.
• The strongest gravitational waves are produced by cataclysmic events such as colliding black holes, supernovae (massive stars exploding at the end of their lifetimes), and colliding neutron stars.

About LIGO detectors

• The Laser Interferometer Gravitational-Wave Observatory (LIGO) is an observatory to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool.
• The observatories help detect gravitational waves by laser interferometry.
• Currently, 2 LIGO observatories are active in the U.S. LIGO-India is a planned advanced gravitational-wave observatory to be located in India as part of the worldwide network. This is being planned at Hingoli District, Maharashtra.
• INDIGO or IndIGO is a consortium of Indian gravitational-wave physicists.