Epsilon Tauri

Epsilon Tauri / Ain
Location of ε Tauri (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Taurus
Right ascension 04h 28m 37.0003s[1]
Declination +19° 10′ 49.563″[1]
Apparent magnitude (V) +3.53[2]
Characteristics
Spectral type K0III[2]
B−V color index 1.014[3]
Astrometry
Radial velocity (Rv)38.420±0.0004[4] km/s
Proper motion (μ) RA: 107.526±0.193 mas/yr[1]
Dec.: −36.200±0.126 mas/yr[1]
Parallax (π)22.3654 ± 0.1721 mas[1]
Distance146 ± 1 ly
(44.7 ± 0.3 pc)
Absolute magnitude (MV)0.145[5]
Details
Mass2.57+0.17
−0.25[6] M☉
Radius12.35+0.41
−0.36[6] R☉
Luminosity78.11+5.68
−5.82[6] L☉
Surface gravity (log g)2.66+0.03
−0.05[6] cgs
Temperature4,950±22[7] K
Metallicity [Fe/H]+0.15±0.02[7] dex
Rotation141.1 days[6]
Rotational velocity (v sin i)3.0[5] km/s
Age625[2] Myr
Other designations
Ain, Oculus Boreus[8], 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
SIMBADdata

Epsilon Tauri or ε Tauri, formally named Ain (/ˈeɪn/),[9] 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.[2] It is claimed to be the heaviest among planet-harboring stars with reliable initial masses.[2] 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.[2]

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.[10]

  1. ^ a b c d Cite error: The named reference GaiaDR3 was invoked but never defined (see the help page).
  2. ^ a b c d e f Cite error: The named reference Sato2007 was invoked but never defined (see the help page).
  3. ^ Cite error: The named reference VizieR was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference BohmVitense2000 was invoked but never defined (see the help page).
  6. ^ a b c d e Cite error: The named reference Teng2023 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Arentoft2019 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference allen was invoked but never defined (see the help page).
  9. ^ "IAU Catalog of Star Names". Retrieved 28 July 2016.
  10. ^ Cite error: The named reference SIMBAD2 was invoked but never defined (see the help page).