Quasars:Discovery and Unusual Quasar

Quasars

 

A Quasar is an extremely luminous active galactic nucleus (AGN) in which a supreme black hole with mass ranging from million to billion times mass of the sun is surrounded by a gaseous accretion disk.

The power radiated by Quasars is enormous and most powerful Quasars have luminosities more than our own Milky Way.

The term Quasars originated as contraction of quasi-stellar radio source because quasars were identified in 1950s as source of radio wave emission of unknown physical origin.

The observed property of Quasar depend upon-

1 Mass of black hole

2 Rate of gas accretion

3 Presence or absence of jet

4 Degree of obscuration by gas

5 Orientation of accretion disk

The peak epoch of Quasar was approximately 10 billion years ago.As of 2017 most distant known quasar is ULAS J1342-0928 at redshift z=7.54

The light was emitted by this Quasar when universe was 690 million years old.

The supper massive black hole in this quasar is 800 million solar masses

The developments of physical understanding about the Quasars was done in 1960s.

Cloud of gas around distant Quasar SDSS

A cosmic mirage named Einstein Cross

The Unusual Quasar

This is direct image of HE 2347-4342 at centre of 7.5*7.5 arcmin 2 sky field.

It is biggest and brightest one known to have formed within 1 billion years of big bang.

There are about 40 known quasars spotted within billion years of big bang.