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Swallowing up of neutron start by black holes

  • Category
    Science & Technology
  • Published
    14th Jul, 2021

A team of international scientists, including those from India, confirms detecting collisions between black holes and neutron stars by analyzing gravitational waves created in January 2020.

Context

A team of international scientists, including those from India, confirms detecting collisions between black holes and neutron stars by analyzing gravitational waves created in January 2020.

  • The gravitational waves were detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the United States and by the Virgo detector in Italy.
  • The research also involved scientists from the LIGO-India Scientific Collaboration (LISC) and the collaboration of other Indian institutions.

Laser Interferometer Gravitational-wave Observatory (LIGO)

  • It is the world's largest gravitational wave observatory and a marvel of precision engineering. Comprising two enormous laser interferometers located 3000 kilometers apart, LIGO exploits the physical properties of light and of space itself to detect and understand the origins of gravitational waves (GW).
  • LIGO is blind: Unlike optical or radio telescopes, LIGO does not see electromagnetic radiation (e.g., visible light, radio waves, microwaves). It doesn't have to because gravitational waves are not part of the electromagnetic spectrum. 
  • A single LIGO detector could not initially confirm gravitational waves on its own.

About

About the key findings

  • Scientists detected the gravitational waves, earlier in 2020, as a result of the two mergers of celestial bodies.
  • Now, it is found that these waves were generated by the process of swallowing neutron stars by the black hole.
  • The first merger involved a black hole about nine times the mass of our sun and a neutron star about 1.9 times the mass of our sun.

Black Hole

  • A black hole is a region of space-time, where gravity is extremely strong that no object can escape from it.
  • Types: There are two types of black holes which become three with the discovery:
    • Stellar-mass black holes: These are the black holes witha mass of fewer than 100 times that of the Sun.
    • Supermassive black holes (SMBH): These are the ones with a mass greater than 100,000 times that of the Sun.
    • Intermediate-mass black holes (IMBHs): These are a class of black holes with a mass approximately 100 to 100,000 times that of the Sun.
  • Both stellar black holes and SMBHs are commonly found.

Neutron Stars

  • Neutron stars are formed when a massive star runs out of fuel and collapses.
  • The very central region of the star, the core, collapses, crushing together every proton and electron into a neutron.
  • If the core of the collapsing star is between about 1 and 3 solar masses, these newly-created neutrons can stop the collapse, leaving behind a neutron star.
  • Stars with higher masses will continue to collapse into stellar-mass black holes.
  • Many neutron stars are likely undetectable because they simply do not emit enough radiation.
  • The location of the first merger in space remains uncertain, with the researchers estimating that it happened somewhere in an area that is 34,000 times the size of a full moon.
  • The second merger involved a 6-solar-mass black hole and a 1.5-solar-mass neutron star.
  • The second event, designated GW200115, originated from the merger of a black hole with a 1.5-solar mass neutron star that took place roughly 1 billion light-years from Earth.
  • It is a new set of binary that merged that was missing.
  • Earlier, it was thought that only the two similar types of bodies could merge such as a black hole and black hole or neutron star with a neutron star.

Significance of the discovery

  • It will be helpful to answer some of the significant questions such as how many of these systems exist, how often they merge, and why we have not yet seen examples in the Milky Way.

Gravitational waves

  • Gravitational waves are ripples in the space-time fabric.
  • These are created by extreme events, such as the collision of two blackholes or two neutron stars.
  • They were first discovered in 2015 and since then observed in the collision between similar cosmic bodies.
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