The Universe: Galaxies
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.
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Featured Article
Supermassive Black Hole at Center of Milky Wa
There is now overwhelming evidence that the center of our Milky Way galaxy contains a giant black hole with a mass of about four million suns. The most convincing data come from the motions of stars...
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Featured Blog Post
Notes from the Astronomy Underground- Astropalooza
According to the tagline in Ridley Scott’s 1979 blockbuster Alien, “In space, no one can hear you scream.” It’s true that sound waves, unlike light, need a medium- some kind of...
Latest News
ESO Very Large Telescope Shows Spectacular Spiral Galaxy in Leo
ESO, Garching, Germany (10 Aug. 2011) – This new picture from ESO’s Very Large Telescope shows NGC 3521, a spiral galaxy located about 35 million light years away in the constellation...
Articles
Introduction Galaxies are now known to contain Supermassive Black Holes in their centers. In most galaxies (pe...
The longest known collimated structures in the universe are the narrow jets that emanate from vicinity of powe...- The galaxy Arp 220 is actually two galaxies that have been caught in the act of merging. Astronomers think tha...
Introduction Galaxies at high redshift often have peculiar shapes, in contrast to the well-developed spiral an...
Introduction BL Lacertae (BL Lac or S4 2200+420) was known to be variable in the visible part of the electroma...
Introduction Galaxy interaction and merging is seen throughout the universe, and it is believed to be an impor...
Introduction The Einstein gravitational theory predicts that light and all other wavelengths of electromagneti...
Blog Posts
A.k.a. The Digital Universe: Now with 10% more dark energy. Things have been rather frenzied this summer, to s...
News Articles
Carnegie Institution for Science (Apr. 23, 2009) Using information from a suite of telescopes, astronomers...
Harvard-Smithsonian Center for Astrophysics (Oct. 22, 2009) Some dramatic galaxies eject gigantic, collima...
GARCHING, GERMANY (Nov. 30, 2009) Which comes first, the supermassive black holes that frantically devour mat...
GARCHING, GERMANY (Nov. 18, 2009) Just as many people are surprised to find themselves packing on unexplained...
NASA JPL, Pasadena, CA (Aug. 20, 2009) For decades, astronomers have gone about their business of studying...
European Southern Observatory, Garching (Sep. 2, 2009) ESO has released a striking new image of a nearby g...
CAMBRIDGE, MA (Jan. 18, 2010) Ultraluminous infrared galaxies have luminosities that exceed a trillion suns. ...
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