Proxima Centauri (Gliese 551)

location of Proxima Centauri

Location of Proxima Centauri.

Proxima Centauri in infrared

Proxima Centauri in infrared. Image by 2-Micron All Sky Survey.

Proxima Centauri (Gliese 551) is the nearest star to the Sun at a distance of 4.24 light-years (268,000 AU, or 40 trillion km). Proxima Centauri is a dim red dwarf of spectral type M, 18,000 times fainter than the Sun. It was discovered in 1915 by Robert Innes.


Proxima Centauri may be gravitationally bound to Alpha Centauri A and B, 0.29 light-years (13,000 AU) away, with an orbital period of 0.5 to 2 million years. Alternatively, it may be on an open (hyperbolic) trajectory past Alpha Centauri that will eventually take it away from the system. According to this idea, Proxima is an independent member of a moving group that includes Alpha Cen A and B and a number of other nearby stars.


Because of its nearness, both to the Sun and its Alpha Cen neighbors, Proxima has well-determined physical properties, including a mass of 0.11 solar masses, a radius of about 15 percent that of the Sun, and an age of 5 to 6 billion years. Despite its considerable age, Proxima has an active chromosphere and is also a flare star (variable-star designation V645 Centauri), capable of brightening a magnitude or more in minutes. Observations of its chromosphere at ultraviolet wavelengths suggest a rotation period of about 31 days. Claims made in the mid-1990s, based on data from the Hubble Space Telescope, that Proxima may be orbited by a large planet or a brown dwarf, have not been substantiated.


distance 4.24 light-years (1.30 pc)
spectral type M5.5Ve
apparent magnitude 11.09
absolute magnitude 15.53
luminosity (Sun = 1) 0.0017
temperature 3,040 K
mass (Sun = 1) 0.12
radius (Sun = 1) 0.14
other designations α Centauri C, V645 Centauri,
GCTP 3278.00, GJ 551,
LHS 49, LFT 1110,
LTT 5721, HIP 70890


Proxima Centauri in science fiction

In Murray Leinster's short story "Proxima Centauri," published in the March 1935 issue of Astounding Stories, a mile-wide starship, The Adastra, approaches the nearest star having made the first interstellar journey from Earth. The crew discover that Proxima is surrounded not only by planets but by a great glowing ring. Their colonization of the system is delayed by having first to deal with a race of intelligent plants.


In both Robert Heinlein's Orphans of the Sky (1963) and Harry Harrison's Captive Universe, generation ships head out for Proxima Centauri.