Epsilon Tauri
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Taurus |
| Right ascension | 04h 28m 37.0003s |
| Declination | +19° 10′ 49.563″ |
| Apparent magnitude (V) | +3.53 |
| Characteristics | |
| Evolutionary stage | red clump |
| Spectral type | K0III |
| B−V color index | 1.014 |
| Astrometry | |
| Radial velocity (Rv) | 38.420±0.0004 km/s |
| Proper motion (μ) | RA: 107.526±0.193 mas/yr Dec.: −36.200±0.126 mas/yr |
| Parallax (π) | 22.3654±0.1721 mas |
| Distance | 146 ± 1 ly (44.7 ± 0.3 pc) |
| Absolute magnitude (MV) | 0.145 |
| Details | |
| Mass | 2.458±0.073 M☉ |
| Radius | 12.46±0.26 R☉ |
| Luminosity | 79.4±3.4 L☉ |
| Habitable zone inner limit | 8.06±0.24 AU |
| Habitable zone outer limit | 15.82±0.47 AU |
| Surface gravity (log g) | 2.66+0.03 −0.05 cgs |
| Temperature | 4,880±67 K |
| Metallicity [Fe/H] | +0.15±0.02 dex |
| Rotation | 141.1 days |
| Rotational velocity (v sin i) | 3.0 km/s |
| Age | 600+150 −50 Myr |
| Other designations | |
| Ain, Oculus Boreus, Epsilon Tau, ε Tau, 74 Tau, BD+18°640, FK5 164, GC 5430, HD 28305, HIP 20889, HR 1409, SAO 93954, CCDM J04286+1911, WDS J04286+1911A | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
Epsilon Tauri or ε Tauri, formally named Ain (/ˈeɪn/), is an orange giant star located approximately 146 light-years (45 parsecs) from the Sun in the constellation of Taurus. An exoplanet (designated Epsilon Tauri b, later named Amateru) is believed to be orbiting the star.
It is a member of the Hyades open cluster. As such its age is well constrained at 625 million years. It is claimed to be the heaviest among planet-harboring stars with reliable initial masses. Given its large mass, this star, though presently of spectral type K0 III, was formerly of spectral type A that has now evolved off the main sequence into the giant phase. It is regarded as a red clump giant; that is, a core-helium burning star.
Since Epsilon Tauri lies near the plane of the ecliptic, it is sometimes occulted by the Moon and (very rarely) by planets.
It has an 11th magnitude companion 182 arcseconds from the primary, although this is an unrelated background star.