  | |
| Observation data EpochJ2000.0 EquinoxJ2000.0 (ICRS) | |
|---|---|
| Constellation | Eridanus |
| Right ascension | 02h 51m 02.32186s[1] |
| Declination | −21° 00′ 14.4654″[1] |
| Apparent magnitude (V) | 4.78[2] |
| Characteristics | |
| Evolutionary stage | red clump[3] |
| Spectral type | K0 III[4] |
| U−Bcolor index | +0.63[2] |
| B−Vcolor index | +0.92[2] |
| Astrometry | |
| Radial velocity (Rv) | −5.9[5] 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[3] |
| 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[5] cgs |
| Temperature | 5,049±20[5] K |
| Metallicity[Fe/H] | 0.08±0.06[5] dex |
| Rotational velocity (v sin i) | 1.11[5] km/s |
| Age | 720±50[6] Myr |
| Other designations | |
| Angetenar, τ2 Eridani,2 Eri,BD−21°509,HD 17824,HIP 13288,HR 850,SAO 168094[7] | |
| Database references | |
| SIMBAD | data |
Tau2 Eridani (τ2 Eridani, abbreviatedTau2 Eri,τ2 Eri), formally namedAngetenar/æŋˈɡɛtənɑːr/,[8][9] is astar in theconstellation ofEridanus. It is visible to the naked eye with anapparent visual magnitude of 4.78.[2] The distance to this star, as determined via theparallax method, is around 187 light-years.
τ2 Eridani (Latinised toTau2 Eridani) is the system'sBayer designation. It is one of a series of stars that share the Bayer designationTau Eridani.
It bore the traditional nameAngetenar, derived from theArabicAl Ḥināyat an-Nahr, 'the Bend in the River', near which it lies.[10] In 2016, the IAU organized aWorking Group on Star Names (WGSN)[11] to catalog and standardize proper names for stars. The WGSN approved the nameAngetenar for this star on 30 June 2017 and it is now so included in the List of IAU-approved Star Names.[9]
InChinese,天苑 (Tiān Yuàn), meaningCelestial Meadows, refers to anasterism 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 andTau9 Eridani.[12] Consequently, theChinese name for Tau2 Eridani itself is天苑九 (Tiān Yuàn jiǔ, English:the Ninth Star of Celestial Meadows.)[13]
Tau2 Eridani is anevolvedK-typegiant star with astellar classification of K0 III.[4] It is ared clump giant on thehorizontal branch of theHertzsprung–Russell diagram, indicating that is it now generating energy through thethermonuclear fusion of helium at its core.[3]
Around 720 million years old, Tau2 Eridani has 2.4 times themass of the Sun and has expanded to over 8 times thesolar radius. It shines with nearly 44 times theSun's luminosity[6] from anouter atmosphere that has aneffective temperature of 5,049 K.[5]
It is a member of the Galacticthin disk population.[5]
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