Proxima Centauri

Proxima Centauri as seen by Hubble.

Proxima Centauri (Latin proxima, meaning "next to" or "nearest to" is a red dwarf, about 4.24 light-years from the Sun, inside the G-cloud, in the constellation of Centaurus. The star was discovered in 1915 by Scottish astronomer Robert Innes, the Director of the Union Observatory in South Africa. Proxima Centauri is the nearest known star to the Sun (hence the name "proxima centauri"), though it is too faint to be seen with the naked eye, with an apparent magnitude of 11.05. Its distance to the second- and third-nearest stars, which form the bright binary Alpha Centauri, is 0.237 ± 0.011 ly (15,000 ± 700 AU). Proxima Centauri is very likely part of a triple star system with Alpha Centauri A and B.

Because of the proximity of this star, its distance from the Sun and angular diameter can be measured directly, from which it can be determined that its diameter is about one-seventh of that of the Sun. Proxima Centauri's mass is about an eight of the Sun's, and its average density is about 40 times that of the Sun. Although it has a very low average luminosity, Proxima is a flare star that undergoes random dramatic increases in brightness because of magnetic activity. The stars magnetic field is created by convection throghout the stellar body, and the resulting flare activity generates a total X-ray emission similar to that produced by the Sun. The mixing of the fuel at Proxima Centauri's core through convection and the star's relatively low energy-production rate suggest that it will be a main-sequence star for another four trillion years, or nearly 300 times the current age of the universe.

On August 24, 2016, it was announced by the European Southern Observatory that a planet orbiting the star, named Proxima Centauri b, was discovered.


Observation dataEdit

  • Constellation: Centaurus
  • Right ascension: 14h 29m 42.9487s

Declinantion: −62° 40′ 46.141″ Apparent magnitude (V): 11.05


  • Spectral type: M5.5 Ve
  • Apparent magnitude (J): 5.35 ± 0.02
  • U-B color index: 1.43
  • B-V color index: 1.90
  • Variable type: Flare star


  • Radial velocity (Rv): -21.7 ± 1.8 km/s
  • Proper motion (μ): RA: −3775.40 mas/yr

Dec.: 769.33 mas/yr

  • Parallax: 768.7 ± 0.3 mas
  • Distance 4.243 light years (1.3009 parasecs)
  • Absolute magnitude (MV): 15.49


  • Mass: 0.123 ± 0.006 Solar mass
  • Radius: 0.141 ± 0.007 Solar radius
  • Luminosity (bolometric): 0.0017 Solar luminosity
  • Surface gravity (log g): 5.20 ± 0.23 cgs
  • Temperature: 3,042 ± 117 K (2768 °C, 5015 °F)
  • Metallicity [Fe/H]: 0.21 dex
  • Rotation: 83.5 days
  • Rotational velocity (v sin i): 2.7 ° 0.3 km/s
  • Age: 4.85 billion years

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