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Proxima Centauri
New shot of Proxima Centauri, our nearest neighbour.jpg
Proxima Centauri as seen by Hubble
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Centaurus
Pronunciation UK: /ˌprɒksɪmə sɛnˈtɔːr/, US: /-ˈtɔːri/
Right ascension 14h 29m 42.94853s
Declination −62° 40′ 46.1631″
Apparent magnitude (V) 10.43 - 11.11
Characteristics
Evolutionary stage Main sequence red dwarf
Spectral type M5.5Ve
Apparent magnitude (U) 14.21
Apparent magnitude (B) 12.95
Apparent magnitude (V) 11.13
Apparent magnitude (R) 9.45
Apparent magnitude (I) 7.41
Apparent magnitude (J) 5.357±0.023
Apparent magnitude (H) 4.835±0.057
Apparent magnitude (K) 4.384±0.033
U−B color index 1.26
B−V color index 1.82
V−R color index 1.68
R−I color index 2.04
J−H color index 0.522
J−K color index 0.973
Variable type UV Ceti ("flare star")
Astrometry
Radial velocity (Rv)−22.204±0.032 km/s
Proper motion (μ) RA: −3775.75 mas/yr Dec.: 765.54 mas/yr
Parallax (π)768.5 ± 0.2 mas
Distance4.244 ± 0.001 ly
(1.3012 ± 0.0003 pc)
Absolute magnitude (MV)15.60
Orbit
PrimaryAlpha Centauri AB
CompanionProxima Centauri
Period (P)547000+6600
−4000
yr
Semi-major axis (a)8700+700
−400
 AU
Eccentricity (e)0.50+0.08
−0.09
Inclination (i)107.6+1.8
−2.0
°
Longitude of the node (Ω)126±5°
Periastron epoch (T)+283+59
−41
Argument of periastron (ω)
(secondary)
72.3+8.7
−6.6
°
Details
Mass0.1221±0.0022 M
Radius0.1542±0.0045 R
Luminosity (bolometric)0.0017 L
Luminosity (visual, LV)0.00005 L
Surface gravity (log g)5.20±0.23 cgs
Temperature3042±117 K
Metallicity [Fe/H]0.21 dex
Rotation82.6±0.1 days
Rotational velocity (v sin i)less than 0.1 km/s
Age4.85 Gyr
Other designations
Alpha Centauri C, CCDM J14396-6050C, GCTP 3278.00, GJ 551, HIP 70890, LFT 1110, LHS 49, LPM 526, LTT 5721, NLTT 37460, V645 Centauri

Proxima Centauri (from Latin, meaning 'nearest [star] of Centaurus'), or Alpha Centauri C, is a red dwarf, a small low-mass star, about 4.244 light-years (1.301 pc) from the Sun in the constellation of Centaurus. It was discovered in 1915 by Robert Innes and is the nearest-known star to the Sun. With a quiescent apparent magnitude of 11.13, it is too faint to be seen with the naked eye. Proxima Centauri forms a third component of the Alpha Centauri system, currently with a separation of about 12,950 AU (1.94 trillion km) and an orbital period of 550,000 years. At present Proxima is 2.18° to the southwest of Alpha Centauri.

Because of Proxima Centauri's proximity to Earth, its angular diameter can be measured directly. The star is about one-seventh the diameter of the Sun. It has a mass about an eighth of the Sun's mass (M), and its average density is about 33 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 star's magnetic field is created by convection throughout 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 its relatively low energy-production rate mean that it will be a main-sequence star for another four trillion years, or nearly 300 times the current age of the universe.

In 2016, the European Southern Observatory announced the discovery of Proxima Centauri b, planet orbiting the star at a distance of roughly 0.05 AU (7.5 million km) with an orbital period of approximately 11.2 Earth days. Its estimated mass is at least 1.3 times that of the Earth. The equilibrium temperature of Proxima b is estimated to be within the range of where water could exist as liquid on its surface, thus placing it within the habitable zone of Proxima Centauri, although because Proxima Centauri is a red dwarf and a flare star, whether it could support life is disputed. Previous searches for orbiting companions had ruled out the presence of brown dwarfs and supermassive planets.

Observation