Tau Andromedae
Tau Andromedae, Latinized from τ Andromedae, is the Bayer designation for a single star in the northern constellation of Andromeda. It has an apparent visual magnitude of +4.94, which is bright enough to be viewed from dark suburban skies. From parallax measurements made during the Gaia mission, the distance to this star can be estimated as roughly 680 light-years (210 parsecs) from Earth. The brightness of this star is diminished by 0.24 in magnitude due to extinction caused by intervening gas and dust. It is drifting closer to the Sun with a radial velocity of −14 km/s.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Andromeda |
| Right ascension | 01h 40m 34.81619s |
| Declination | +40° 34′ 37.3397″ |
| Apparent magnitude (V) | +4.94 |
| Characteristics | |
| Spectral type | B5 III |
| U−B color index | −0.41 |
| B−V color index | −0.09 |
| Astrometry | |
| Radial velocity (Rv) | −13.9±2.6 km/s |
| Proper motion (μ) | RA: 17.889(178) mas/yr Dec.: −20.981(95) mas/yr |
| Parallax (π) | 4.7804 ± 0.1304 mas |
| Distance | 680 ± 20 ly (209 ± 6 pc) |
| Details | |
| Luminosity | 851 L☉ |
| Surface gravity (log g) | 3.357±0.020 cgs |
| Temperature | 12,680±100 K |
| Rotational velocity (v sin i) | 74±13 km/s |
| Age | 217 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
The spectrum of this star matches a stellar classification of B5 III, with the luminosity class of III indicating that this is a giant star. It is radiating about 851 times the luminosity of the Sun from its photosphere at an effective temperature of 12,670 K. The star is an estimated 217 million years old and is spinning with a high projected rotational velocity of ~74 km/s.