Tau Octantis
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Octans |
| Right ascension | 23h 28m 03.7855s |
| Declination | −87° 28′ 55.967″ |
| Apparent magnitude (V) | 5.50 |
| Characteristics | |
| Spectral type | K2 III |
| U−B color index | +1.43 |
| B−V color index | +1.27 |
| Astrometry | |
| Radial velocity (Rv) | 31.0±1.4 km/s |
| Proper motion (μ) | RA: +16.782 mas/yr Dec.: +11.957 mas/yr |
| Parallax (π) | 6.8009±0.0574 mas |
| Distance | 480 ± 4 ly (147 ± 1 pc) |
| Absolute magnitude (MV) | −0.36 |
| Details | |
| Mass | 1.14 M☉ |
| Radius | 24 R☉ |
| Luminosity | 223 L☉ |
| Surface gravity (log g) | 1.63 cgs |
| Temperature | 4,422 K |
| Metallicity [Fe/H] | +0.12 dex |
| Rotational velocity (v sin i) | <1 km/s |
| Other designations | |
| τ Oct, 81 G. Octantis, CPD−88°204, FK5 925, GC 32558, HD 219765, HIP 115836, HR 8862, SAO 258970 | |
| Database references | |
| SIMBAD | data |
Tau Octantis, Latinized from τ Octantis, is a solitary star in the southern circumpolar constellation Octans. It has an apparent magnitude of 5.50, allowing it to be faintly seen with the naked eye. The object is located at a distance of 480 light years but is receding with a heliocentric radial velocity of 31 km/s.
Tau Octantis has a stellar classification of K2 III, indicating that the object is a red giant. It has 114% the mass of the Sun but is 223 times as luminous. However, an enlarged radius of 24 R☉ yields an effective temperature of 4,422 K, giving it an orange glow. Tau Octantis has an iron abundance 132% that of the Sun and is believed to be a member of the old disk population. Currently, it spins with a projected rotational velocity less than 1 km/s.