- Sagittarius A
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Strongest source of cosmic radio waves, lying in the direction of the constellation Sagittarius.Discovered by Karl Jansky in 1932, it has been identified as the nucleus of the Milky Way Galaxy. The region is relatively small and constitutes an intense source of infrared radiation thought to be emitted partly by stars and partly by dust around them. Within the region is a much smaller radio source, Sagittarius (Sgr) A*, which appears to mark the centre of the Galaxy. Observations indicate that the galactic nucleus contains a black hole with a mass of one million to several million times that of the Sun; they also provide a strong case that Sgr A* is the black hole. The activity at the Galaxy's centre resembles that of an active galactic nucleus but on a much smaller scale.
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strongest source of cosmic radio waves in the Milky Way Galaxy, originating from the direction of the constellation Sagittarius. One component of the source, known as Sagittarius A West, has been identified as coming from the direction of the nucleus of the Milky Way Galaxy. Most of the radio radiation is from a synchrotron mechanism, indicating the presence of free electrons and magnetic fields. A compact, extremely bright central point source is designated Sagittarius A*. X-ray, infrared (infrared radiation), spectroscopic, and radio interferometric investigations have indicated the very small dimensions of this region. Infrared observations of stars orbiting around the position of Sagittarius A* demonstrate the presence of a black hole with a mass equivalent to 4,310,000 Suns (Sun). These properties are similar to those of other galaxies with active nuclei (e.g., Seyfert galaxies (Seyfert galaxy)) but on a smaller scale.Paul W. Hodge* * *
Universalium. 2010.
