Quasars and Active Galactic Nuclei

Quasar Properties and Origins

• The emission from an active galactic nucleus (AGN) in a quasar is thought to be powered by the accretion of material onto a supermassive black hole.

Quasar Redshifts

• The redshifts of quasars originate from the expansion of the universe, with quasars being extremely luminous objects at large cosmic distances.

Quasar Terminology

• The term 'quasi-stellar object' (QSO) refers to quasars because they appear as point-like objects, similar to stars, but have much higher luminosities.

Quasar Locations

• High-resolution imaging, particularly from the Hubble Space Telescope, has revealed that quasars are often located at the centers of galaxies.

Quasar Emission

• The emission from an active galactic nucleus (AGN) in a quasar is thought to be powered by the accretion of material onto a supermassive black hole.

Quasar Properties

• The observed properties of a quasar are dependent on the orientation of the AGN, the amount of dust and gas in the surrounding environment, and the distance of the quasar.

Quasar Identification

• Over 200,000 quasars have been identified with reliable spectroscopic redshifts.

Quasar Detection

• Quasar ULAS J1342+0928 was detected at a redshift of 7.54, making it one of the most distant quasars observed.

Quasar Light

• The light observed from quasar Pōniuāʻena was emitted around 13.4 billion years ago, when the universe was still in its early stages.

Quasar Activity

• The peak epoch of quasar activity occurred around 10-12 billion years ago, during a period of intense galaxy formation and supermassive black hole growth.