Why in News?
The discovery of gravitational wave from a pair of neutron star – black hole (NS-BH) collisions by LIGO Scientific Collaboration (LSC) was reported in the Astrophysical Journal Letters on June 29, 2021.
What are Gravitational Waves?
- Gravitational waves are ripples in space-time caused by some of the most violent and energetic processes in the Universe like –
- Neutron stars orbiting each other
- Merger of Neutron Star-Black Hole (NS-BH)
- Merger of two black holes
- Explosion of a star as a supernova
- These waves travel at the speed of light, carrying with them information about their origins as well as clues to the nature of gravity itself.
- These were predicted by Albert Einstein in 1916 in his theory of relativity and on September 14, 2015 the World’s first direct detection of these waves was achieved.
- The technique used to detect the signals is called matched filtering.
What is Black Hole?
A Black Hole is a region of space time where gravity is so strong that no particle or electromagnetic radiation such as light can escape from it.
What is Neutron Star?
A Neutron Star is the collapsed core of a massive supergiant star, shedding their outer layers in a supernova explosions. The immense gravitational pressure squeeze their electrons and protons into neutrons.
Importance of detection of Gravitational Wave
It will answer following question:
- Is general relativity the correct theory of relativity?
- How does matter behave under extreme densities and pressures?
- How abundant are stellar-mass black holes?
- What is the central engine driving gamma ray busts?
- What happens when a massive star collapses?
Observations of Collision (NS-BH)
- A neutron start has a surface and black hole does not.
- It was for the first time that LIGO Scientific Collaboration discovered the gravitational waves from a pair of NS-BH mergers.
- The inference from data as to how often they merge gives clues about their orgin and how they (binaries) were formed.
- The observations help scientists understand the formation and relative abundance of binaries (NS-BH).
- The discovery of NS-BH collisions is a historic moment for the scientific community. These findings can help to understand the behaviour of matter at extreme densities, probe effects under extreme gravity if black holes emit extremely periodic pulses.
- In the Indian context, the discovery will significantly led the LIGO India to improve the sky localization of these events. The chance of observation of these distant sources using electromagnetic telescopes will be increased, which in turn, will give us more precise measurement of how fast the universe is expanding.