2 Centauri
Star in the constellation Centaurus
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2 Centauri is a single[11] star in the southern constellation of Centaurus, located approximately 183 light-years from Earth.[1] It has the Bayer designation g Centauri;[10] 2 Centauri is the Flamsteed designation. This object is visible to the naked eye as faint, red-hued star with an apparent visual magnitude of about 4.2. It is moving away from the Earth with a heliocentric radial velocity of +41 km/s.[6] The star is a member of the HR 1614 supercluster.[12]
  | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Centaurus |
| Right ascension | 13h 49m 26.72175s[1] |
| Declination | −34° 27′ 02.7929″[1] |
| Apparent magnitude (V) | 4.16–4.26[2] |
| Characteristics | |
| Evolutionary stage | AGB[3] |
| Spectral type | M5 III[4] |
| U−B color index | +1.44[5] |
| B−V color index | +1.49[5] |
| Variable type | SRb[2] |
| Astrometry | |
| Radial velocity (Rv) | +40.7±0.7[6] km/s |
| Proper motion (μ) | RA: −41.68±0.23[1] mas/yr Dec.: −59.77±0.18[1] mas/yr |
| Parallax (π) | 17.82±0.21 mas[1] |
| Distance | 183 ± 2 ly (56.1 ± 0.7 pc) |
| Absolute magnitude (MV) | +0.51[7] |
| Details | |
| Mass | 1.0[8] M☉ |
| Radius | 82.4[9] R☉ |
| Luminosity | 767[8] L☉ |
| Surface gravity (log g) | 0.65[8] cgs |
| Temperature | 3,438[8] K |
| Other designations | |
| g Centauri, 2 Cen, V806 Cen, CD−33°9358, GC 18666, HD 120323, HIP 67457, HR 5192, SAO 204875[10] | |
| Database references | |
| SIMBAD | data |
This is an evolved red giant star with a stellar classification of M5 III.[4] In 1951, Alan William James Cousins announced that the star, then called g Centauri, is a variable star.[15] It was given its variable star designation, V806 Centauri, in 1978.[16] It is classified as a semiregular variable star and its brightness varies from magnitude +4.16 to +4.26[2] with a period of 12.57 days.[17] The star has around 82 times the Sun's radius and is radiating 767 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,438 K.