3C273 is a quasar located in the constellation Virgo. It is the optically-brightest quasar in our sky (m ~ 12.9), and one of the closest with a redshift, z, of 0.16. It is also the most luminous quasar known, with an absolute magnitude of -26.7. 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. 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 3C273 has a substantial redshift, placing it several billion light years away. This article is about a celestial body. ... This view, taken with infrared light, is a false-color image of a quasar-starburst tandem with the most luminous starburst ever seen in such a combination. ... Orion is a remarkable constellation, visible from most places on the globe (but not always the whole year long). ... See VIRGO (physics) for a French-Italian project in physics. ... See also list of optical topics. ... The apparent magnitude (m) of a star, planet or other heavenly body is a measure of its apparent brightness; that is, the amount of light received from the object. ... Redshift describes a change in the wavelength of light, in which the wavelength is longer than when it was emitted at the source. ... In astronomy, absolute magnitude is the apparent magnitude, m, an object would have if it were at a standardized distance away. ... Right ascension (RA; symbol α: Greek letter alpha) is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. ... The University of Cambridge is the second-oldest university in the English-speaking world. ... The Third Cambridge Catalog of Radio Sources (3C) is an astronomical catalogue of celestial radio sources, was published in 1959 by the University of Cambridge. ... 1959 was a common year starting on Thursday (link will take you to calendar). ... 1963 was a common year starting on Tuesday (link will take you to calendar). ... Maarten Schmidt (born December 28, 1929) is a Dutch astronomer who discovered objects in the universe called quasars. ... Nature is one of the oldest and most reputable general-purpose scientific journals, first published on November 4, 1869. ... Redshift describes a change in the wavelength of light, in which the wavelength is longer than when it was emitted at the source. ... A light year, abbreviated ly, is the distance light travels in one year: roughly 9. ...

Prior to the discovery of 3C273, several other radio sources had been associated with optical counterparts, the first being 3C48. 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. 3C273 was the first object to be identified as what we now know quasars to be--extremely luminous objects at cosmological distances. 3C48 was the first source in the Third Cambridge (3C) radio survey for which an optical identification was found (by Allan Sandage in 1960). ... Most stars are of nearly constant luminosity. ... A blazar is a galaxy with a very compact and highly variable energy source at the center of the host galaxy. ... Coma Berenices (Latin for Berenices Hair) is a traditional asterism that has since become a constellation. ... Canes Venatici (Latin for hunting dogs) is a small northern constellation that was introduced by Johannes Hevelius in the 17th century. ...

3C273 is a radio-loud quasar, and was also one of the first extragalactic X-ray sources discovered in 1970. The luminosity is variable at nearly every wavelength from radio waves to Gamma rays on timescales of a few days to decades. Polarization has been observed in radio, infrared, and optical light, suggesting that a fraction of the emitted light is synchrotron radiation, 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 3C273 have revealed proper motion of some of the radio emitting regions, further suggesting the presence of relativistic jets of material. In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... 1970 was a common year starting on Thursday. ... In physics, luminosity is the density of luminous intensity in a given direction. ... The wavelength is the distance between repeating units of a wave pattern. ... Radio frequency, or RF, refers to that portion of the electromagnetic spectrum in which electromagnetic waves can be generated by alternating current fed to an antenna. ... This article is about electromagnetic radiation. ... This article treats polarization in electrodynamics. ... Synchrotron radiation refers to electromagnetic radiation similar to cyclotron radiation, but generated by electrons moving at highly relativistic speeds. ... An artists impression of a black hole with a closely orbiting companion star that exceeds its Roche limit. ... An accretion disc (or accretion disk) is a structure formed by material falling into a gravitational source. ... This article needs cleanup. ... The proper motion of a star is the motion of the position of the star in the sky (the change in direction in which we see it, as opposed to the radial velocity) after eliminating the improper motions of the stars, which affect their measured coordinates but are not real...

3C273 is located at (J2000) right ascension 12h 29m 6.7s, declination +2d 3m 8.6s, and is visible in May in both the northern and southern hemispheres. It is bright enough to be observed with larger amateur telescopes. Right ascension (RA; symbol α: Greek letter alpha) is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. ... In astronomy declination (dec) is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. ... This article is about the month of May. ... Amateur astronomy, often called back yard astronomy, is a hobby whose participants enjoy observing celestial objects. ...