Gravitational Wave Observations

[pib] Narrow-Line Seyfert 1 (NLS1) Galaxy

Note4Students

From UPSC perspective, the following things are important :

Prelims level : NLS1 Galaxy

Mains level : Black holes and gravitation waves

Astronomers have discovered a new active galaxy identified as the farthest gamma-ray emitting galaxy that has so far been stumbled upon. This active galaxy called the Narrow-Line Seyfert 1 (NLS1) galaxy.

Try this PYQ:

Q.Recently, scientists observed the merger of giant ‘blackholes’ billions of light-years away from the Earth. What is the significance of this observation?

(a) ‘Higgs boson particles’ were detected.

(b) ‘Gravitational waves’ were detected.

(c) Possibility of inter-galactic space travel through ‘wormhole’ was confirmed.

(d) It enabled scientists to understand ‘singularity’.

NLS1 Galaxy

  • Indian scientists have studied around 25,000 luminous Active galactic nuclei (AGN) from the Sloan Digital Sky Survey (SDSS).
  • They identified it as a gamma-ray emitting NLS1 galaxy, which is a rare entity in space.
  • It is about 31 billion light-years away, opens up avenues to explore more such gamma-ray emitting galaxies that wait to meet us.

What makes it intriguing?

  • Ever since 1929, when Edwin Hubble discovered that the Universe is expanding, it has been known that most other galaxies are moving away from us.
  • Light from these galaxies is shifted to longer (and this means redder) wavelengths – in other words, it is red-shifted.
  • Scientists have been trying to trace such red-shifted galaxies to understand the early Universe.
  • Powerful relativistic jets, or sources of particles in the Universe travelling nearly at speed to light, are usually produced by AGN powered by large black holes and hosted in a giant elliptical galaxy.

Why NLS1 is unique?

  • NLS1s are a unique class of AGN that are powered by the black hole of low mass and hosted in a spiral galaxy.
  • As of today, gamma-ray emission has been detected in about a dozen NLS1 galaxies, which are a separate class of AGN identified four decades ago.
  • All of them are at redshifts lesser than one, and no method was present to date to find NLS1 at redshifts larger than one.
  • This discovery opens up a new way to find gamma-ray emitting NLS1 galaxies in the early Universe.
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