Astrophysics (index)about


(QSO, quasi-stellar object)
(distant, bright object that appears something like a star)

A quasar (from quasi-stellar object or QSO) is an object with the point-like appearance of a star, but with a redshift indicating a far greater distance than that of a visible individual star. Quasars are identified now as active galactic nuclei. Observed redshifts range from .05 to greater than 7, putting them in the range of 600 million to near 13 billion light-years distant (or years old).

They appear bright enough that some quasars might equal the Sun's apparent brightness as seen from Earth at a distance of 30 light-years. However, they do not necessarily shine so brightly in all directions. Their strong light can be lensed by nearer objects and can be useful for studying the objects doing the lensing.

Quasars were first identified in the 1960s.

The Balmer series, typically H-alpha, is often useful to determine the redshift.

The term quasi-stellar source (or QSS or quasi-stellar radio source, also sometimes using the prefix QSR) refers to a quasar that is also a strong radio source In fact, the term quasar was originally coined for such radio sources, but is often used with the broader meaning. The term quasi-stellar galaxy (QSG) formerly was used for radio-quiet quasars. (Note that in radio astronomy, the word source is typically assumed to mean radio source).

(stars,galaxies,AGN,object type,jets)
QSOQSO B1957+405quasargeneral prefix
QSRQSR J1819+3845quasargeneral for "radio-loud quasar"
QuasarQuasar J192748.6+735802quasargeneral prefix

Referenced by:
accretion rate
astronomical catalog
Balmer series
Blandford-Znajek mechanism (BZ process)
Baryon Oscillation Spectroscopic Survey (BOSS)
Blandford-Payne mechanism (BP process)
Canada-France High-z Quasar Survey (CFHQS)
Cygnus A (3C 405)
deep field (DF)
deep survey
Dark Energy Spectroscopic Instrument (DESI)
Eddington luminosity
epoch of reionization (EOR)
star formation feedback
gravitational collapse
gravitational lensing
Gunn-Peterson trough
Hamburg/ESO Survey (HE)
hyperluminous infrared galaxy (HLIRG)
hot DOG
Hamburg Schmidt Survey (HS)
intensity mapping
Large Bright QSO Survey (LBQS)
luminous infrared galaxy (LIRG)
large quasar group (LQG)
Lyman-alpha forest
NASA/IPAC Extragalactic Database (NED)
Palomar Four-filter Survey (PC)
Pico dos Dias Survey (PDS)
Palomar-Green Survey (PG)
radio star
rare designator prefixes
relativistic beaming
retrograde accretion
radio galaxy (RG)
Second Byurakan Survey (SBS)
Sloan Digital Sky Survey (SDSS)
Seyfert galaxy
Soltan argument
spectral signature
3C 273
3C 48
3C 9
Tonantzintla Surveys (Ton)
2dF Galaxy Redshift Survey (2dFGRS)
2dF-SDSS LRG and QSO survey (2SLAQ)
ultraluminous infrared galaxy (ULIRG)
X-ray source (RS)