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Merger of two black holes

Topics Covered: Awareness in space.

Merger of two black holes:


Gravitational waves from a collision between two black holes were detected in 2019 at the gravitational wave observatory LIGO (United States) and the detector Virgo (Italy).

  • It was calculated to have come from roughly 17 billion light years away, and from a time when the universe was about half its age.

What’s unique about this meger?

One of the two parent black holes was of an unusual “intermediate mass”, which challenges traditional scientific knowledge. It is the first “intermediate mass” black hole ever observed.

What are Gravitational Waves?

They are invisible ripples that form when a star explodes in a supernova; when two big stars orbit each other; and when two black holes merge.

  • Travelling at the speed of light, gravitational waves squeeze and stretch anything in their path.
  • Proposed by Albert Einstein in his General Theory of Relativity over a century ago.
  • It was only in 2015, however, that the first gravitational wave was actually detected — by LIGO.

What is a black hole?

A black hole is an object in space that is so dense and has such strong gravity that no matter or light can escape its pull. Because no light can escape, it is black and invisible.

  • There’s a boundary at the edge of a black hole called the event horizon, which is the point of no return — any light or matter that crosses that boundary is sucked into the black hole. It would need to travel faster than the speed of light to escape, which is impossible.
  • Anything that crosses the event horizon is destined to fall to the very centre of the black hole and be squished into a single point with infinite density, called the singularity.

What is LIGO?

It is a massive observatory for detecting cosmic gravitational waves and for carrying out experiments.

  • The objective is to use gravitational-wave observations in astronomical studies.
  • The project operates three gravitational-wave (GW) detectors. Two are at Hanford, Washington, north-western US, and one is at Livingston in Louisiana, south-eastern US.
  • The proposed LIGO India project aims to move one advanced LIGO detector from Hanford to India.


Prelims Link:

  1. About the General Theory of Relativity.
  2. When was the first gravitational wave detected?
  3. LIGO- mission objectives, observatories and funding.
  4. What are event horizon and singularity in the context of a black hole?
  5. LIGO India- proposed site, partners and objectives.
  6. Where is Virgo locator located?

Mains Link:

Discuss the applications and significance of findings of the Laser Interferometer Gravitational-Wave Observatory (LIGO) detector.


Sources: the Hindu.