Alpha Centauri A, a yellow main-sequence star in Centaurus
Alpha Centauri A is a yellow main-sequence star in the constellation Centaurus. At 4.4 light years away, it is the 4th brightest star in the Earth's sky, where it shines at an apparent visual magnitude of -0.01.
Alpha Centauri A (HIP 71683)
Alpha Centauri A is a yellow main-sequence star in the constellation Centaurus. At 4.4 light years away, it is the 4th brightest star in the Earth's sky, where it shines at an apparent visual magnitude of -0.01. Alpha Centauri A is the primary component of a multiple-star system. The star's age is estimated to be 9.2 billion years but is certainly no less than 8.1 billion years and no greater than 10.2 billion years. The iron abundance of Alpha Centauri A is +0.2 (158.5% of the Sun). It is moving through the Galaxy at a speed of 31.9 km/s relative to the Sun. Its projected Galactic orbit carries it between 23,700 and 33,700 light years from the center of the Galaxy. It will come closest to the Sun 28,000 years from now when it will brighten to magnitude -0.66 from a distance of 3.3 light years.
Sky position: RA 14h 39.7m, Dec -60° 50.4'
Common designations: Alpha Centauri A, Rigel Kentaurus, HIP 71683, HD 128620, HR 5459, Gliese 559 A
New astronomy book
explores our Galaxy!
Vistas of Many Worlds
On sale now!
Brightest stars in Centaurus:
(list all)
1
| -0.01
) Alpha Centauri A
| Rank | Mag. | Star |
| 2 | 0.61 | Hadar |
| 3 | 1.35 | Alpha Centauri B |
| 4 | 2.06 | Menkent |
| 5 | 2.20 | Gamma Centauri |
| 6 | 2.29 | Epsilon Centauri |
| 7 | 2.33 | Eta Centauri |
| 8 | 2.55 | Zeta Centauri |
| 9 | 2.58 | Delta Centauri |
| 10 | 2.75 | Iota Centauri |
| 11 | 3.11 | Lambda Centauri |
| 12 | 3.13 | Kappa Centauri |
| 13 | 3.41 | Nu Centauri |
| 14 | 3.47 | Mu Centauri |
| 15 | 3.83 | Phi Centauri |
| 16 | 3.85 | Tau Centauri |
| 17 | 3.87 | Upsilon-1 Centauri |
Galactic Orbit of Alpha Centauri A
(compared to the Sun)
E
ccentricity: 17.3% vs. 16.0%Angle φ : -27.2°vs. 26.0°
Semi-major axis : 8,805 pc vs. 8,686 pc
Semi-minor axis: 8,671 pc vs. 8,574 pc
Focus-to-center
: 1,527 pcvs. 1,388 pcSemilatus rectum : 8,540 pc vs. 8,464 pc
Perigalacticon: 7,278 pc vs. 7,297 pc
Apogalacticon
: 10,332 pcvs. 10,074 pcSome Tabulated XHIP Data for Alpha Centauri A
(see also: SIMBAD)
Astrometry
2007A&A...474..653V
| Position | Proper Motion | |
| Right Ascension: | 219.92041034° ±1.42 mas | -3,678.19 ±1.51 mas/yr. |
| Declination: | -60.83514707° ±1.08 mas | 481.84 ±1.24 mas/yr. |
| Galactic Longitude: | 315.74187646° | -3,168.06 mas/yr. |
| Galactic Latitude: | -0.68432932° | 1,929.94 mas/yr. |
Parallax: 742.12 ± 1.40 mas
Spectrography
Spectral Type: G2V 2006A&A...460..695T.
Radial Velocity:
-21.40 ±0.76 km/s [A rating]
2005ApJS..159..141V.
This star is a spectroscopic binary with a solved orbit.
Iron Abundance [Fe/H]:
0.20 ±0.01 dex
2011A&A...530A.138C, 2007A&A...465..271R, 2006MNRAS.370..163B, 2005ApJS..161..444T, 2005ApJS..159..141V, 2005A&A...437.1127S, 2004A&A...420..183A, 2001A&A...367..253F, 1997A&A...323..809F, 1996A&A...314..191G, 1993A&A...275..101E, 1988A&A...206..100A, 1988A&A...190..148E.
Photometry
| band | magnitude | Abs. Mag. |
| U | ||
| B | 0.70 | 5.05 |
| V | -0.01 | 4.34 |
| R | ||
| I | -0.70 | 3.65 |
| J | ||
| H | ||
| K |
B-V: +0.71 V-I: +0.69
Derivations
Heliocentric distance: 1.35 pc (0.2% margin of error)
Galactocentric distance: 7,399 pc
Transverse velocity: 23.7 km/s
3D heliocentric position and motion:
|
toward: |
Galactic center | Galactic rotation | North Galactic Pole |
| Position ( X, Y, Z) | 1.0 pc | -0.9 pc | 0.0 pc |
| Velocity (U, V, W) | -29.3 km/s | 0.3 km/s | 12.6 km/s |