A galaxy is a principal component of our universe. It is made up of stars, an interstellar medium of gas and dust and a large number of stars, ranging from a few tens of million to as many as a trillion. Stars may congregate in clusters, associations and in spiral arms. Galaxies are also thought to contain vast amounts of dark matter, extending beyond the distribution of stars. Galaxies are held together by gravity including that due to the dark matter. Most galaxies are 1,000 to 100,000 parsecs (3000 to 300,000 light-years) in diameter and are usually separated by distances on the order of millions of parsecs. There are about 100 billion galaxies in the visible Universe. When capitalized, Galaxy refers to our own Milky Way Galaxy.
Dense Gas in Ultraluminous Infrared GalaxiesLast Updated on 2010-01-18 at 13:59CAMBRIDGE, MA (Jan. 18, 2010) – Ultraluminous infrared galaxies have luminosities that exceed a trillion suns. (For comparison, the Milky Way's luminosity is only that of... More »
Black hole zapping a galaxy into existenceLast Updated on 2009-11-30 at 11:27GARCHING, GERMANY (Nov. 30, 2009) – Which comes first, the supermassive black holes that frantically devour matter or the enormous galaxies where they reside? A brand new... More »
Baffling Galactic BulgeLast Updated on 2009-11-19 at 17:01GARCHING, GERMANY (Nov. 18, 2009) – Just as many people are surprised to find themselves packing on unexplained weight around the middle, astronomers find the evolution of... More »
Radio Galaxies: Early UniverseLast Updated on 2009-11-11 at 17:09Radio galaxies are cosmic beacons, with the brightest ones beaming nearly a trillion solar-luminosities of radiation into space at radio wavelengths. The origin of this intense... More »
Seven Billion Year-old GalaxiesLast Updated on 2009-11-11 at 16:28
As modern telescopes peer more and more deeply into the universe, they are seeing older and older galaxies. The current record is a galaxy whose light has been traveling towards... More »