Quasar 3C 273

Object Description

Quasar 3C 273
Quasar 3C 273: Detail of the jet with the Canada-France-Hawaii (left) and the Hubble Space Telescope (right) [106]

3C 273 is the brightest known example of a «quasi-stellar radio source» or in short: Quasar. It is a strong radio source that looks like a faint star in the telescope. The spectrum shows an enormous redshift of z = 0.158, which indicates that this object is moving away from us at around 47'400 km/s or 15.8% of the speed of light. With a Hubble constant of 75 km/s/Mpc, the quasar is about two billion light years away from us.

In 1963 3C 273 was covered by the moon. Since then it has been known that this is a dual radio source and that the two radio components can be identified with optically visible details. The star-like component is the main component, but about 90% of the radio energy comes from the foggy streak or «jet» southwest of the object. The jet starts about 11" from the bright center and continues about another 10" and is about 1" to 2" wide. If the distance from the quasar is correct, then this jet is about 300'000 light years long.

Quasar 3C 273
Quasar 3C 273: Image taken with the Hubble Space Telescope, 2003. © NASA/ESA, J. Bahcall (IAS) [213]

The stellar component of 3C 273 has a radio core about 0.5" in diameter and is surrounded by a 3" halo. Assuming the distance is correct, the diameter of the radio core should be around 7'500 light years. The enormous energy output of such a relatively small object is difficult to explain. But a new problem arises: The stellar component shows fluctuations in brightness of around 0.5 magnitudes with half a period of around 13 years, but also sudden increases for a week or so. It is difficult to understand how an object of galactic dimensions can exhibit such rapid changes in brightness when it takes centuries for light to cross the object. This suggests that the true source must have a diameter of a few light months. [70, 90, 92, 95, 106, 111, 124]

Data from Simbad [145]
Designations 3C 273, PGC 41121, QSO J1229+0203
Right Ascension (J2000.0) 12 29 6.6
Declination (J2000.0) +02 03 08
Magnitudes B 13.05, V 14.830, R 14.11, G 12.844090, J 11.692, H 10.953, K 9.937, u 13.859, g 12.990, r 12.871, i 12.630, z 13.242
Redshift z 0.158339

The term «3C» refers to the number in the Third Cambridge Catalog of Radio Sources, published in 1959 by the Royal Astronomical Society in London. The quasar is also listed under the designation PGC 41121 in the «Principal Galaxies Catalog».

Finder Chart

The map below shows the position of quasar 3C 273 in the constellation Virgo. Once you are in the correct section of the sky, the 1° and 15' excerpts from the STScI Digitized Sky Survey help with the precise identification of the quasar, as it does not differ visually from the surrounding stars.

Finder Chart Quasar 3C 273
Quasar 3C 273 in constellation Virgo. Charts created using SkySafari 6 Pro and STScI Digitized Sky Survey. Limiting magnitudes: Constellation chart ~6.5 mag, DSS2 close-ups ~20 mag. [149, 160]

Visual Observation

300 mm Aperture: This really extremely exotic deep-sky object is much easier to track down and view than it appears at first glance - the sight of a 12.3 to 12.8 bright little star is all the more frustrating, which is why no sketch was made. Nothing can be recognized from the said jet, which seems to be asking a lot. The quasar is very clearly visible with an aperture of 300 mm, probably even down to an aperture of 150 mm. — 1996, Bernd Nies

Objects Within a Radius of 15°


  • [70] Tracking Down A Quasar by Phil Harrington; Astronomy 6/94, p.56
  • [90] Hunt Down A Quasar; Astronomy 4/96, p.64
  • [92] Have Astronomers Solved The Quasar Enigma? by Ken Croswell; Astronomy 2/93, p.28
  • [95] Objekte der Saison: 3C 273 von Klaus Veit; Interstellarum2/96, S.50
  • [106] Resolving a Quasar's Jet; S&T 3/94, p.12
  • [111] A Catalog of Quasars Near and Far by Geoffrey Burbidge and Adelaide Hewitt; S&T 12/94, p.32
  • [124] Quasar 3C 273 im Achtzöller von Michael Grosse; SuW 4/88, S.246
  • [145] SIMBAD astronomical database; simbad.u-strasbg.fr/simbad
  • [149] SkySafari 6 Pro, Simulation Curriculum; skysafariastronomy.com
  • [160] The STScI Digitized Sky Survey; archive.stsci.edu/cgi-bin/dss_form
  • [213] Quasar 3C 273; esahubble.org/images/opo0303c (2020-12-31)