Epsilon Tauri
 The position of ε Tauri in the Taurus constellation. | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Taurus |
| Right ascension | 04h 28m 37.00s[1] |
| Declination | +19° 10′ 49.5″[1] |
| Apparent magnitude (V) | +3.53 |
| Characteristics | |
| Spectral type | K0III |
| B−V color index | 1.014 |
| Astrometry | |
| Proper motion (μ) | RA: 106.19 ± 0.38[1] mas/yr Dec.: -37.84 ± 0.30[1] mas/yr |
| Parallax (π) | 22.24 ± 0.25[1] mas |
| Distance | 147 ± 2 ly (45.0 ± 0.5 pc) |
| Details | |
| Mass | 2.7 ± 0.1 M☉ |
| Radius | 12.692 ± 0.545 [2] R☉ |
| Luminosity | 97 ± 8[3] L☉ |
| Temperature | 4901 ± 20 K |
| Metallicity | +0.17 ± 0.04 |
| Age | 625 × 106 years |
| Other designations | |
Epsilon Tauri (ε Tau, ε Tauri) is an orange giant star, spectral type of K0 III, located approximately 147 light-years[1] away from the Sun in the constellation of Taurus. It is a member of the Hyades open cluster. It has the traditional names Ain (Arabic عين), or Oculus Borealis, both of which mean "eye".
It has an 11th magnitude companion 182 arcseconds from the primary.
Since Epsilon Tauri lies near the plane of the ecliptic, it is sometimes occulted by the Moon and (very rarely) by planets.
As a member of the Hyades cluster, Epsilon Tauri's age is well constrained at 625 million years.[3] Given its large mass, this star was formerly a member of spectral type A that has now evolved off the main sequence into the giant phase. It is regarded as a red clump that burns helium at its core.
Planetary system
In 2007 a massive extrasolar planet was reported orbiting the star. The planet orbits Epsilon Tauri every 1.6 years in a somewhat eccentric orbit. At the time of the discovery it was the only known planet in an open cluster.[4] No other planets have yet been detected in the Hyades cluster, but another planetary system—Iota Horologii— belongs to the Hyades stream and may be an escaped member of the cluster.
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | >7.6 (± 0.2) MJ | 1.93 (± 0.03) | 594.9 (± 5.3) | 0.151 (± 0.023) | — | — |
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. Vizier catalog entry
- ↑ Gerard T. van Belle and Kaspar von Braun (2009). "Directly Determined Linear Radii and Effective Temperatures of Exoplanet Host Stars" (abstract). The Astrophysical Journal 694 (2): 1085–1098. arXiv:0901.1206. Bibcode:2009ApJ...694.1085V. doi:10.1088/0004-637X/694/2/1085.(web Preprint)
- ↑ 3.0 3.1 3.2 Sato, Bun'ei et al. (2007). "A Planetary Companion to the Hyades Giant ε Tauri". The Astrophysical Journal 661 (1): 527–531. Bibcode:2007ApJ...661..527S. doi:10.1086/513503.
- ↑ "Notes for star eps Tau". The Extrasolar Planets Encyclopaedia. Retrieved 2007-02-09.
External links
- "Notes for star eps Tau". The Extrasolar Planets Encyclopaedia. Retrieved 2008-06-24.
- "Star Names". Frosty Drew Observatory. Retrieved 2008-06-24.
- Epsilon Tauri at the SIMBAD Astronomical Database.
Coordinates: 
04h 28m 37.0s, +19° 10′ 49″
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