HD 12139 is an orange-hued star in the northern zodiac constellation of Aries. With an apparent visual magnitude of 5.89, it is a dim star that is just visible to the naked eye under good viewing conditions. It is located approximately 351 light-years (107.5 pc) distant from the Sun, based on parallax,[2] but is drifting closer with a radial velocity of −2 km/s.[1] With high probability, it is considered a member of the Hercules stream.[6]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aries |
| Right ascension | 01h 59m 35.68394s[1] |
| Declination | 21° 03′ 30.8472″[1] |
| Apparent magnitude (V) | 5.89[2] |
| Characteristics | |
| Spectral type | K0III-IV[3] |
| B−V color index | 1.031±0.015[2] |
| Astrometry | |
| Radial velocity (Rv) | −1.65±0.20[1] km/s |
| Proper motion (μ) | RA: +141.014[1] mas/yr Dec.: -14.643[1] mas/yr |
| Parallax (π) | 9.3049 ± 0.0967 mas[1] |
| Distance | 351 ± 4 ly (107 ± 1 pc) |
| Absolute magnitude (MV) | 0.50[2] |
| Details | |
| Mass | 1.69±0.48[4] M☉ |
| Radius | 11.12+0.34 −0.13[1] R☉ |
| Luminosity | 58.2±0.7[1] L☉ |
| Surface gravity (log g) | 2.50±0.11[4] cgs |
| Temperature | 4,780+120 −70[1] K |
| Metallicity [Fe/H] | −0.02±0.05[4] dex |
| Age | 2.0+1.0 −0.6[4] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
This object is an aging red giant[7] with a stellar classification of K0III-IV,[3] meaning that it has used up its core hydrogen and is expanding. At present it has 11[1] times the girth of the Sun. The star is about two[4] billion years old with 1.7[4] times the mass of the Sun. It is radiating 58[1] times the luminosity of the Sun from its photosphere at an effective temperature of 4,780 K.[1]
A magnitude 9.36 companion is located at an angular separation of 199.70″ from the primary along a position angle of 9°, as of 2015. It is unclear if the two are physically associated.[8]
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