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The red dwarf Proxima Centauri (also Alpha Centauri
C), part of the Alpha Centauri star system, is the nearest
star to Earth, other than the Sun. As the name suggests, it is located in the constellation of Centaurus.
Based on the parallax of 772.33 ± 2.42 milliarcsec measured by Hipparcos, Proxima Centauri is roughly 4.22 light years from Earth (40 Pm), 270,000 times more distant than
the Sun.
In 2002, VLTI used optical interferometry to measure the angular diameter of
Proxima Centauri as 1.02 ± 0.08 milliarcsec. Knowing its distance, the actual diameter can be determined to be about 1/7 that of
the Sun, or 1.5 times that of Jupiter. The mass is also about
1/7 that of the Sun, or 150 times that of Jupiter.
Its apparent magnitude is 11 (very weak, as red dwarfs in
general are: far too weak to be observable with the naked eye). Proxima Centauri was discovered in 1915 by Robert Innes while he was Director of the Republic Observatory in Johannesburg,
South Africa.
Proxima Centauri has often been suggested as a logical first destination for interstellar travel.
Proxima Centauri is about 13,000 astronomical units away from
Alpha Centauri (this is about 2 Pm, or 0.2 light years, or about 1/20 of the distance between Alpha Centauri and the Sun) and may be in orbit about it, with a period on the order of 500,000 years or more. For this reason, Proxima is
sometimes referred to as Alpha Centauri C. However, it is not clear if it really is in orbit, although the association is
unlikely to be entirely accidental as it shares approximately the same motion through space as the larger star system.
See also:
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