3C 273 is a quasar or quasi-stellar object (QSO) in Virgo. Hold your mouse cursor over the image to see its location in the image.

Although appearing to look like a star, a quasar is really the tremendously bright nucleus of an extremely distant galaxy. Quasars are not completely understood, but scientists believe that they are associated with a supermassive black hole in the center of their host galaxy that powers an active galactic nucleus.

Originally discovered as a radio source in 1963, Maarten Schmidt examined the spectrum of 3C 273 and realized that it was strongly redshifted, receding from us at 16 percent of the speed of light. This indicated that it was very far away. At that distance and brightness, he realized it was unlikely to be a star and theorized that it was the bright nucleus of a distant galaxy.

Today it is thought that 3C 273 lies at a distance of 2.5 billion light-years, making it one of the closest quasars to us. This is still incredibly far away. The nearest star to the Sun is Proxima Centauri at a distance of 4 light-years. Galaxy M31 lies at a distance of 2.5 million light-years. 3C 273 is 1,000 times farther away than M31.

At this distance, its apparent magnitude of 12.8 would correspond to an absolute brightness of -26.7. Its luminosity is more than 2 trillion times brighter than the Sun and 100 times that of a large galaxy. Quasars are the most luminous objects known in the universe.

3C 273 can vary in brightness from magnitude 11.7 to 13.2, but it is the brightest quasar visible, and the farthest object that is easily visible in amateur telescopes.

3C 273's size, however, is only 1 light-year in diameter. This compares to the Milky Way Galaxy's diameter of 100,000 light-years. 3C 273 is also believed to have a mass of nearly 1 billion solar masses.

3C 273 lies at the center of a giant 16th-magnitude elliptical galaxy that has an apparent size of 30 arcseconds. The galaxy itself is not seen in the image at the top of this page, only the quasar is visible.

3C 273 was the first quasar to be identified. It derives its numerical designation from being the 273rd object listed in the third Cambridge Catalog of radio sources. This catalog was published in 1959.

North is to the top in the above image.

3C 273 Catalogs: 3C 273, PGC 41121, HIP 60936 Object Type: Quasar Magnitude: 12.8 Size: Stellar Constellation: Virgo Image Field Centered At: RA: 12h 29m 03s Dec: +02° 01' 51"