First intermediate mass black hole observed

On 21 May 2019, scientists have discovered GW190521 by three interferometers (two in US at Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo interferometer in Italy). The detection of GW190521 has been published on 2 September 2020. 

What is unique about GW190521?

It is first detected intermediate mass black hole. Till now, scientists have not found black holes with mass 100 to 1000 times the mass of Sun. The mass of GW190521 is 142 times the mass of Sun.

How was GW190521 formed?

Over seven billion years ago, the collision of two black holes of 85 and 65 solar masses led to the formation of GW190521. The collision produced gravitational waves same to energy of eight suns.  

What is the significance of the discovery of GW190521?

The discovery of GW190521 is significant because of its large mass and the large mass of the black holes that formed it. The discovery of GW190521 challenges existing knowledge that Black holes in the range 60 to 120 solar masses cannot be formed by the gravitational collapse of a star. This is because at the size range of 60 to 120 solar masses, stars undergo supernova explosion and get completely destroyed. Two black holes that formed GW190521 were in the range of 60 to 120 solar masses and still they formed large black hole.

What are Black holes?

Black holes are objects with a strong gravitational pull. The strong gravitational pull of Black holes does not allow particles or electromagnetic radiations such as light to pass through them.

What are the classes/types of black holes?

There are four classes of black holes. They are stellar, intermediate, supermassive and miniature (micro).

• Stellar-class black holes: Collapse of a dying star causes the formation of stellar-class black holes. They are 3 to 10 solar masses in size. They are also called collapsars.
• Intermediate-class black holes: Their mass is more than stellar class black holes but less than supermassive black holes. Their mass is in the range of 10²-10⁵ solar masses. One solar mass is approximately equal to 2 X 10³⁰
• Supermassive black holes: Supermassive black holes are present at the centre of most galaxies, including the Milky Way. Milky Way has Sagittarius A at its centre.
• Miniature (micro) black holes: They are hypothetical black holes.

What are Interferometers?

Interferometers are instruments based on the phenomenon of interference. They detect changes thousand times smaller than an atomic nucleus as gravitational waves pass Earth. They work according to the principle of superposition and the phenomenon of interference. Superposition of two or more waves produces an interference pattern that can be analyzed.

Why are gravitational waves used to detect black holes?

Gravitational waves are completely different from electromagnetic radiations such as visible light, X-rays, radio waves, etc. Black holes cannot be detected with electromagnetic radiation. Electromagnetic radiations interact with matter and show properties of reflection, bending, refraction, absorption. But, Gravitational waves show very weak interaction with the matter and are not interrupted when they pass through the Universe. 

What are gravitational waves?

Gravitational waves are defined as disturbances in space-time produced by the collision of black holes and supernova explosion. Einstein predicted gravitational waves in the general theory of relativity in 1916.

When were gravitational waves directly detected first time?

Rainer Weiss, Barry Barish and Kip Thorne directly detected gravitational waves for the first time in 2015 and won the 2017 Nobel Prize in physics for directly detecting gravitational waves for the first time.