Epsilon Tauri

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**ε Tauri**
Observation data Equinox J2000.0
Constellation	Taurus
Right ascension	04^h 28^m 37.0^s
Declination	+19° 10' 49"
Apparent magnitude (V)	+3.53
Distance	155 ± 6 ly (48 ± 2 pc)
Spectral type	K0III
Other designations
Ain, Oculus Borealus, 74 Tauri, HR 1409, HD 28305, BD+18 640, FK5 164, HIP 20889, SAO 93954, GC 5430, CCDM 04286+1911

Epsilon Tauri (ε Tau / ε Tauri) is a star in the constellation Taurus and a member of the Hyades open cluster. It has the traditional names Ain (Arabic عين), or Oculus Borealus, both of which mean "eye". Another traditional name is Coronis (Greek Κορωνις), referring to one of the Hyades sisters.

ε Tau belongs to the spectral class K0 and has apparent magnitude +3.6. It is 155 light years away from the Sun, has a luminosity of 90 times that of the Sun and a radius of 13 times solar. The surface temperature of this star is measured at 4925 kelvins. It has an 11th magnitude companion 182 arcseconds from the primary.

Since ε Tau lies near the plane of the ecliptic, it is sometimes occulted by the Moon and (very rarely) by planets.

[edit] The planet

In 2007 a massive extrasolar planet was reported orbiting the star. The planet orbits ε 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.