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Alpha Centauri

Alpha Centauri A/B The position of Alpha Centauri A and Alpha Centauri B Observation data Epoch J2000.0      Equinox J2000.0 Constellation Centaurus Alpha Centauri A Right ascension 14h 39m 36.4951s Declination –60° 50' 02.308? Apparent magnitude (V) -0.01 Alpha Centauri B Right ascension 14h 39m 35.0803s Declination –60° 50' 13.761? Apparent magnitude (V) +1.33 Characteristics Spectral type G2 V U-B color index +0.23 B-V color index +0.69 Characteristics Spectral type K1 V U-B color index +0.63 B-V color index +0.90 Astrometry Radial velocity (Rv) -21.6 km/s Proper motion (µ) RA: -3678.19 mas/yr Dec.: 481.84 mas/yr Parallax (p) 747.1 ± 1.2 mas Distance 4.366 ± 0.007 ly (1.339 ± 0.002 pc) Absolute magnitude (MV) 4.38 / 5.71 Details Alpha Centauri A Mass 1.100 M? Radius 1.227 R? Luminosity 1.519 L? Surface gravity (log g) 4.30 cgs Temperature 5790 K Metallicity 151% Sun Rotation ~22.5 ± 5.9 days Age 6 ± 1 Gyr Alpha Centauri B Mass 0.907 M? Radius 0.865 R? Luminosity 0.500 L? Surface gravity (log g) 4.37 cgs Temperature 5260 K Metallicity 160% Sun Rotation 47 days Orbit Companion Alpha Centauri AB Period (P) 79.91 ± 0.011 yr Semi-major axis (a) 17.57 ± 0.022" Eccentricity (e) 0.5179 ± 0.00076 Inclination (i) 79.205 ± 0.041° Longitude of the node (O) 204.85 ± 0.084° Periastron epoch (T) 1875.66 ± 0.012 Argument of periastron (?) (secondary) 231.65 ± 0.076° Other designations Database references SIMBAD data Exoplanet Archive data ARICNS data Extrasolar Planets Encyclopaedia data From Earth to Alpha Centauri. Alpha Centauri (a Centauri, a Cen; also known as Rigil Kent /'ra?d??l 'k?nt/—see Names) or Toliman is the brightest star in the southern constellation of Centaurus and the third brightest star in the night sky. The Alpha Centauri system is located 1.34 parsecs or 4.37 light years from the Sun, making it the closest star system to our Solar System. Although it appears to the unaided eye as a single object, Alpha Centauri is actually a binary star system (designated Alpha Centauri AB or a Cen AB) whose combined visual magnitude of -0.27 makes it the third brightest star (other than the Sun) seen from Earth after the -1.46 magnitude Sirius and the -0.72 magnitude Canopus.Its component stars are named Alpha Centauri A (a Cen A), with 110% of the mass and 151.9% the luminosity of the Sun, and Alpha Centauri B (a Cen B), at 90.7% of the Sun's mass and 44.5% of its luminosity. During the pair's 79.91-year orbit about a common center, the distance between them varies from about that between Pluto and the Sun to that between Saturn and the Sun.A third star, known as Proxima Centauri, Proxima, or Alpha Centauri C (a Cen C), is probably gravitationally associated with Alpha Centauri AB. Proxima is at the slightly smaller distance of 1.29 parsecs or 4.24 light years from the Sun, making it the closest star to the Sun even though it is not visible to the naked eye. The separation of Proxima from Alpha Centauri AB is about 0.06 parsecs, 0.2 light years or 13,000 astronomical units (AU); equivalent to 400 times the size of Neptune's orbit.The system may also contain at least one planet, the Earth-sized Alpha Centauri Bb, which, if confirmed, will be the closest known exoplanet to Earth. The planet has a mass at least 13% more than Earth's and orbits Alpha Centauri B with a period of 3.236 days. Orbiting at a distance of 6 million kilometers from the star, 4% of the distance of the Earth to the Sun and a tenth of the distance between Mercury and the Sun, the planet has an estimated surface temperature of 1500 K (roughly 1200 °C), too hot to be habitable. More recently, on June 10, 2013, scientists reported that the earlier claims of an Earth-like exoplanet orbiting Alpha Centauri B may not be supported. Cite error: There are tags on this page, but the references will not show without a {{reflist}} template (see the help page).
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