Proxima Centauri
Proxima Centauri is a small, low-mass star located 4.2465 light-years (1.3020 pc) away from the Sun in the southern constellation of Centaurus. Its Latin name means the 'nearest [star] 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 unaided eye. Proxima Centauri is a member of the Alpha Centauri star system, being identified as component Alpha Centauri C, and is 2.18° to the southwest of the Alpha Centauri AB pair. It is currently 12,950 AU (0.2 ly) from AB, which it orbits with a period of about 550,000 years.
False color Hubble Space Telescope WFPC2 image taken in 2013. The bright lines are diffraction spikes. | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Centaurus |
| Pronunciation | /ˌprɒksəmə sɛnˈtɔːri/ or /ˈprɒksɪmə sɛnˈtɔːraɪ/ |
| Right ascension | 14h 29m 42.946s |
| Declination | −62° 40′ 46.16″ |
| Apparent magnitude (V) | 10.43 – 11.11 |
| Characteristics | |
| Evolutionary stage | Main sequence |
| Spectral type | M5.5Ve |
| 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 Cet + BY Dra |
| Astrometry | |
| Radial velocity (Rv) | −22.204±0.032 km/s |
| Proper motion (μ) | RA: −3781.741 mas/yr Dec.: 769.465 mas/yr |
| Parallax (π) | 768.0665 ± 0.0499 mas |
| Distance | 4.2465 ± 0.0003 ly (1.30197 ± 0 pc) |
| Absolute magnitude (MV) | 15.60 |
| Orbit | |
| Primary | Alpha Centauri AB |
| Companion | Proxima 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 | |
| Mass | 0.1221±0.0022 M☉ |
| Radius | 0.1542±0.0045 R☉ |
| Luminosity (bolometric) | 0.001567±0.000020 L☉ |
| Luminosity (visual, LV) | 0.00005 L☉ |
| Surface gravity (log g) | 5.20±0.23 cgs |
| Temperature | 2,992+49 −47 K |
| Metallicity [Fe/H] | 0.21 dex |
| Rotation | 89.8±4 days |
| Rotational velocity (v sin i) | < 0.1 km/s |
| Age | 4.85 Gyr |
| Other designations | |
Alf Cen C, Alpha Centauri C, V645 Centauri, GJ 551, HIP 70890, CCDM J14396-6050C, LFT 1110, LHS 49, LPM 526, LTT 5721, NLTT 37460 | |
| Database references | |
| SIMBAD | data |
| ARICNS | data |
Proxima Centauri is a red dwarf star with a mass about 12.5% of the Sun's mass (M☉), and average density about 33 times that of the Sun. Because of Proxima Centauri's proximity to Earth, its angular diameter can be measured directly. Its actual diameter is about one-seventh (14%) the diameter of the Sun. Although it has a very low average luminosity, Proxima Centauri is a flare star that randomly undergoes 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 internal mixing of its fuel by convection through its core, and Proxima's relatively low energy-production rate, mean that it will be a main-sequence star for another four trillion years.
Proxima Centauri has two known exoplanets and one candidate exoplanet: Proxima Centauri b, Proxima Centauri d and the disputed Proxima Centauri c. Proxima Centauri b orbits 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 1.07 times that of Earth. Proxima b orbits within Proxima Centauri's habitable zone—the range where temperatures are right for liquid water to exist on its surface—but, because Proxima Centauri is a red dwarf and a flare star, the planet's habitability is highly uncertain. A candidate super-Earth, Proxima Centauri c, roughly 1.5 AU (220 million km) away from Proxima Centauri, orbits it every 1,900 d (5.2 yr). A sub-Earth, Proxima Centauri d, roughly 0.029 AU (4.3 million km) away, orbits it every 5.1 days.