Narrow-Line Seyfert 1 (NLS1) Galaxy

Q Why is it in News ? 

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.

Q What are details about 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.

Q 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.

Q  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.