3C 273
Quasar 3C 273, with its jet (Image by Chandra X-ray Observatory)
Observation data (Epoch J2000)
Constellation	Virgo
Right ascension	12h 29m 06.7s[1]
Declination	+02° 03′ 09″[1]
Redshift	0.158339 ± 0.000067[1]
Distance	2.443 Gly (749 Mpc)[2][3]
Type	Blazar; Sy1[1]
Apparent magnitude (V)	12.9[1]
Notable features	optically-brightest quasar, first spectrum of a quasar
Other designations
PGC 41121[1] and HIP 60936
See also: Quasar, List of quasars
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3C 273 is a quasar located in the constellation Virgo. It was the first quasar ever to be identified.

It is the optically brightest quasar in our sky (m ~12.9), and one of the closest with a redshift, z, of 0.158.^[4] A luminosity distance of D_L = 749 megaparsecs (2.4 Gly) may be calculated from z.^[3] It is also one of the most luminous quasars known, with an absolute magnitude of −26.7, meaning that if it was only as distant as Pollux (~10 parsecs) it would appear nearly as bright in the sky as the Sun. Its mass has been measured to be 886 ± 187 million solar masses through broad emission-line reverberation mapping.^[5]

Large-scale jet [link]

The quasar has a large-scale visible jet, which measures ~200 kly (60 kpc) long, having an apparent size of 23″.^[3] In 1995 optical imaging of the jet using the Hubble Space Telescope revealed a structured morphology evidenced by repeated bright knots interlaced by areas of weak emission.^[3]

History [link]

The name signifies that it was the 273rd object (ordered by right ascension) of the Third Cambridge Catalog of Radio Sources (3C), published in 1959. After accurate positions were obtained using lunar occultation by Cyril Hazard at the Parkes Radio Telescope,^[6] the radio source was quickly associated with an optical counterpart, an unresolved stellar object. In 1963, Maarten Schmidt and Bev Oke published a pair of papers in Nature reporting that 3C 273 has a substantial redshift, placing it several billion light-years away.

Prior to the discovery of 3C 273, several other radio sources had been associated with optical counterparts, the first being 3C 48. Also, many active galaxies had been misidentified as variable stars, including the famous BL Lac, W Com, and AU CVn. However, it wasn't understood what these objects were, since their spectra were unlike those of any known stars. Its spectrum did not resemble that of any normal stars with typical stellar elements. 3C 273 was the first object to be identified as what we now know quasars to be — extremely luminous objects at cosmological distances.

3C 273 as imaged by the Hubble Space Telescope's Advanced Camera for Surveys. Credit: NASA/ESA.

3C 273 is a radio-loud quasar, and was also one of the first extragalactic X-ray sources discovered in 1970. However, even to this day, the process which gives rise to the X-ray emissions is controversial.^[3] The luminosity is variable at nearly every wavelength from radio waves to Gamma rays on timescales of a few days to decades. Polarization with coincident orientation has been observed in radio, infrared, and optical light being emitted from the large-scale jet; these emissions are therefore almost certainly synchrotron in nature,^[3] radiation that is created by a jet of charged particles moving at relativistic speeds. Such jets are believed to be created by the interaction of the central black hole and the accretion disk. VLBI radio observations of 3C 273 have revealed proper motion of some of the radio emitting regions, further suggesting the presence of relativistic jets of material.

3C 273 is visible in May in both the northern hemisphere and southern hemispheres. It is bright enough to be observed with larger amateur telescopes. Due in part to its radio luminosity and its discovery as the first identified quasar, 3C 273's right ascension in the Fifth Fundamental Catalog (FK5) is used to standardize the positions of 23 extragalactic radio sources used to define the International Celestial Reference System (ICRS).^[7]

Trivia [link]

• 'To the quasar', a song by Dutch project-band Ayreon is about quasar 3C 273. The song is found on the album 'Universal Migrator Part 2: Flight of the Migrator'.
• Given its distance from Earth and visual magnitude, 3C 273 is the most distant celestial object average amateur astronomers are likely to see through their telescopes.

References [link]

External links [link]

• 3C 273's Database at the INTEGRAL Science Data Centre (ESA)
• Detailed CCD image of 3C 273 based on 30 min total exposure
• Amateur 3C 273 Redshift Measurement
• NightSkyInfo.com - 3C 273
• 3C 273 at ESA/Hubble
• SKY-MAP.ORG SDSS image of 3C 273
• The Quasar 3C 273: Spring 2005 - Variable Star Of The Season AAVSO
• 3C 273 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

Coordinates: 12^h 29^m 06.7^s, +02° 03′ 09″