galactic halo

galactic halo
In astronomy, a nearly spherical volume of thinly scattered stars, globular clusters, and tenuous gas observed surrounding spiral galaxies.

It may extend far beyond the disk and contain most of the galaxy's mass. The halo of the Milky Way Galaxy is thought to have a radius greater than 100,000 light-years and to be predominantly composed of dark matter.

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      in astronomy, nearly spherical volume of thinly scattered stars, globular clusters of stars, and tenuous gas observed surrounding spiral galaxies, including the Milky Way (Milky Way Galaxy)—the galaxy in which the Earth is located. The roughly spherical halo of the Milky Way is thought to have a radius of some 50,000 light-years (about 5 × 1017 kilometres), and its gas is a source of radio emission, particularly at the 21-centimetre wavelength (see 21-centimetre radiation).

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Universalium. 2010.

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