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. First noticed in the 1960s, quasars are now identified to be active galactic nuclei. Observed redshifts range from 0.05 to greater than 7, putting them in the range of 600 million to near 13 billion light-years distant (and years old). The Balmer series, typically H-alpha, is often useful to determine the redshift. 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.

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. The terms radio loud quasar (RLQ) and radio quiet quasar (RQQ) are also used. 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)
Further reading:
QSOQSO B1957+405general prefix
QSRQSR J1819+3845general for "radio-loud quasar"
QuasarQuasar J192748.6+735802general prefix

Referenced by pages:
accretion rate
astronomical catalog
Balmer series (H)
black hole mass function (BHMF)
Blandford-Znajek mechanism (BZ process)
Baryon Oscillation Spectroscopic Survey (BOSS)
Calán/Tololo Supernova Survey
celestial reference frame
Canada-France High-z Quasar Survey (CFHQS)
Cygnus A (3C 405)
dark matter
direct collapse black hole (DCBH)
deep field (DF)
deep survey
Dark Energy Spectroscopic Instrument (DESI)
damped Lyman alpha absorber (DLA)
Deep Multicolor Survey (DMS)
Eddington luminosity
epoch of reionization (EOR)
extragalactic astronomy
Catalogues of Fundamental Stars
star formation feedback
Giant Gemini GMOS survey (GGG survey)
gravitational collapse
gravitational potential energy
gravitational lensing
GRS 1915+105
Gunn-Peterson trough
Hamburg/ESO Survey (HE)
high-energy astrophysics (HEA)
hyperluminous infrared galaxy (HLIRG)
hot DOG
Hamburg Schmidt Survey (HS)
International Celestial Reference System (ICRS)
intensity mapping
intergalactic dust
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)
Penrose Compton scattering (PCS)
Palomar-Green Survey (PG)
PG 1302-102
radio star
rare designator prefixes
relativistic beaming
retrograde accretion
radio galaxy (RG)
Second Byurakan Survey (SBS)
Sloan Digital Sky Survey (SDSS)
Seyfert galaxy (Sy)
supermassive black hole (SMBH)
SMBH formation
Soltan argument
spectral signature
3C 273
3C 279
3C 48
3C 9
Tonantzintla Surveys (Ton)
2dF Galaxy Redshift Survey (2dFGRS)
2dF-SDSS LRG and QSO survey (2SLAQ)
James Webb Space Telescope (JWST)
X-ray source