Galactic Center
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The Galactic Center is the rotational center of the Milky Way galaxy. It is located at a distance of about 8 kiloparsecs in the brightest part of the Milky Way, in the direction of the constellation Sagittarius.
Because of cool interstellar dust along the line of sight, the Galactic Center cannot be studied at visible, ultraviolet or soft X-ray wavelengths. The available information about the Galactic Center comes from observations at gamma ray, hard X-ray, infrared, sub-millimetre and radio wavelengths.
The complex radio source Sagittarius A appears to be located almost exactly at the Galactic Center, and contains an intense compact radio source, Sagittarius A*, which many astronomers believe may coincide with a supermassive black hole at the center of our Galaxy. Accretion of gas onto the black hole, probably involving a disk around it, would release energy to power the radio source, itself much larger than the black hole. The latter is too small to see (in silhouette, of course) with present instruments.
Work presented in 2002 by Antony Stark and Chris Martin mapping the gas density in a 400 light year region around the galactic center has revealed an accumulating ring with a mass several million times that of the Sun and near the critical density for star formation. They predict that in approximately 200 million years there will be an episode of starburst in the galactic center, with many stars forming rapidly and undergoing supernovas at a hundred times the current rate. The starburst may also be accompanied by the formation of galactic jets as matter falls into the central black hole. It is thought that the Milky Way undergoes a starburst of this sort every 500 million years.
The coordinates of Galactic Center in the Equatorial coordinate system are: RA 17h45m40.04s, Dec -29º 00' 28.1" (J2000 epoch).
See also
External links
- UCLA Galactic Center Group (http://www.astro.ucla.edu/research/galcenter/)
- Max Planck Institute for Extraterrestrial Physics Galactic Center Group (http://www.mpe.mpg.de/ir/GC/)
- Dramatic Increase in Supernova Explosions Looms (http://www.space.com/scienceastronomy/astronomy/boom_times_020610-1.html)ja:銀河核