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Tau2 Eridani (τ2 Eridani, abbreviated Tau2 Eri, τ2 Eri), formally named Angetenar /æŋˈɡɛtənɑːr/,[8][9] is a star in the constellation of Eridanus. It is visible to the naked eye with an apparent visual magnitude of 4.78.[2] The distance to this star, as determined via the parallax method, is around 187 light-years.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Eridanus |
| Right ascension | 02h 51m 02.32186s[1] |
| Declination | −21° 00′ 14.4654″[1] |
| Apparent magnitude (V) | 4.78[2] |
| Characteristics | |
| Spectral type | K0 III[3] |
| U−B color index | +0.63[2] |
| B−V color index | +0.92[2] |
| Astrometry | |
| Radial velocity (Rv) | −5.9[4] km/s |
| Proper motion (μ) | RA: −38.52[1] mas/yr Dec.: −16.05[1] mas/yr |
| Parallax (π) | 17.45 ± 0.20 mas[1] |
| Distance | 187 ± 2 ly (57.3 ± 0.7 pc) |
| Absolute magnitude (MV) | 1.008[5] |
| Details | |
| Mass | 2.39±0.03[6] M☉ |
| Radius | 8.85±0.08[6] R☉ |
| Luminosity | 44.36±0.8[6] L☉ |
| Surface gravity (log g) | 2.95±0.03[4] cgs |
| Temperature | 5,049±20[4] K |
| Metallicity [Fe/H] | 0.08±0.06[4] dex |
| Rotational velocity (v sin i) | 1.11[4] km/s |
| Age | 720±50[6] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
τ2 Eridani (Latinised to Tau2 Eridani) is the system's Bayer designation. It is one of a series of stars that share the Bayer designation Tau Eridani.
It bore the traditional name Angetenar, derived from the Arabic Al Ḥināyat an-Nahr, 'the Bend in the River', near which it lies.[10] In 2016, the IAU organized a Working Group on Star Names (WGSN)[11] to catalog and standardize proper names for stars. The WGSN approved the name Angetenar for this star on 30 June 2017 and it is now so included in the List of IAU-approved Star Names.[9]
In Chinese, 天苑 (Tiān Yuàn), meaning Celestial Meadows, refers to an asterism consisting of Tau2 Eridani, Gamma Eridani, Pi Eridani, Delta Eridani, Epsilon Eridani, Zeta Eridani, Eta Eridani, Pi Ceti, Tau1 Eridani, Tau3 Eridani, Tau4 Eridani, Tau5 Eridani, Tau6 Eridani, Tau7 Eridani, Tau8 Eridani and Tau9 Eridani.[12] Consequently, the Chinese name for Tau2 Eridani itself is 天苑九 (Tiān Yuàn jiǔ, English: the Ninth Star of Celestial Meadows.)[13]
Tau2 Eridani is an evolved K-type giant star with a stellar classification of K0 III.[3] It is a red clump giant on the horizontal branch of the Hertzsprung–Russell diagram, indicating that is it now generating energy through the thermonuclear fusion of helium at its core.[5]
Around 720 million years old, Tau2 Eridani has 2.4 times the mass of the Sun and has expanded to over 8 times the solar radius. It shines with nearly 44 times the Sun's luminosity[6] from an outer atmosphere that has an effective temperature of 5,049 K.[4]
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