Observations confirm neutron star merger:

Observations confirm neutron star merger:

Context:

For the first time, a cosmic event has been observed with gravitational waves and also light waves.

Introduction:

• The LIGO-VIRGO collaboration, three members of which won this year’s physics Nobel Prize, detected the merger of two neutron stars –extremely dense, massive but tiny, objects.

Observations:

• Gamma rays bursting from the event were observed by nearly 70 ground and space-based observations.
• The second part of the discovery- the observation of Gamma ray bursts by several telescopes includes the observations by the Giant Metreware Radio Telescope (GMRT), the Himalayan Chandra Telescope (HCT) and AstroSat.
• The CZTI instrument on AstroSat helped narrow down the location of the gamma-ray flashes.
• Observations which were made earlier by LIGO have been of black hole mergers, and as no light can escape from a black hole, there was no such light counterpart to the measurements.
• The GMRT played a key role in understanding jet physics and refining models of radio emission from the remnant formed by the merging neutron stars.

Importance of discovery:

• Neutron-star mergers are incredibly rich and complex phenomena.
• Every  area of physics and astrophysics can learn something from this unique laboratory set up by nature.

Outcomes of discovery:

• The gravitational waves and the gamma ray burst, which light waves are arrived at nearly the same time indicate that the speed of gravitational waves is extremely close to the speed of light.
• This was predicted by Einstein, but it is the first time we are making a direct measurement.
• The neutron stars of the signal detected were located about 130 million light years away.
• These neutron stars emitted gravitational waves that were detectable for about 100 seconds.
• When they collided, a flash of light in the form of gamma rays was emitted.
• This gamma rays burst was seen on Earth about two seconds after the gravitational wavers were observed.
• The detection of a neutron star merger was surprising, because neutron stars are much smaller than black holes and their mergers produce much weaker gravitational waves than do black hole mergers.
• The observations have given  astronomers  an unprecedented opportunity       to probe a collision of two neutron stars

Neutron stars:

• Neutron stars are the smallest, densest stars known to exist.
• These could be about 20 kilometres in diameter and have masses much greater than the Sun.
• A teaspoonful  of neutron star material could hold a mass of a billion tonnes.
• They are formed when massive stars explode in supernovae.
• As these neutron stars spiraled together, they emitted gravitational wave that were detectable for about 100 seconds, when they collided, a flash of light in the form of gamma rays was emitted and seen on Earth about two seconds after the gravitational waves.

About LIGO:

• The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a large-scale physics experiment and observatory to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool
• The LIGO-VIRGO collaboration includes about 1,500 scientists and of this about 40 are Indians.
• LIGO is the largest and most ambitious project ever funded by the NSF( National Science Foundation).