Andromeda I
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Andromeda I is a dwarf spheroidal galaxy (dSph)[1] about 2.40[2] million light-years away in the constellation Andromeda. Andromeda I is part of the local group of galaxies and a satellite galaxy of the Andromeda Galaxy (M31). It is roughly 3.5 degrees south and slightly east of M31.[3] As of 2005, it is the closest known dSph companion to M31[4] at an estimated projected distance of ~40[2] kpc or ~150,000[3] light-years.
Andromeda I was discovered by Sidney van den Bergh[5] in 1970 with the Mount Palomar Observatory 48-inch telescope.[1] Further study of Andromeda I was done by the WFPC2 camera of the Hubble Space Telescope. This found that the horizontal branch stars, like other dwarf spheroidal galaxies were predominantly red.[6] From this, and the abundance of blue horizontal branch stars, along with 99 RR Lyrae stars detected in 2005,[4] lead to the conclusion there was an extended epoch of star formation. The estimated age is approximately 10 Gyr. The Hubble Space Telescope also found a globular cluster in Andromeda I, being the least luminous galaxy where such a cluster was found.[7]
See also
References
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External links
Template:Sky Template:Andromeda galaxy Template:Andromeda (constellation)