Epsilon Andromedae

ε Andromedae
Location of ε Andromedae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Andromeda
Right ascension 00h 38m 33.347s
Declination +29° 18′ 42.31″
Apparent magnitude (V) 4.357
Characteristics
Evolutionary stage red clump
Spectral type G6 III Fe−3 CH1
U−B color index +0.463
B−V color index +0.8713
V−R color index +0.6
R−I color index +0.51
Astrometry
Radial velocity (Rv)−84.43±0.15 km/s
Proper motion (μ) RA: −228.701 mas/yr
Dec.: −253.206 mas/yr
Parallax (π)19.2451±0.1188 mas
Distance169 ± 1 ly
(52.0 ± 0.3 pc)
Absolute magnitude (MV)+0.69
Details
Mass1.01±0.35 M☉
Radius9.04±0.34 R☉
Luminosity51.3 L☉
Surface gravity (log g)2.88±0.02 cgs
Temperature5,082±20 K
Metallicity [Fe/H]−0.53±0.05 dex
Rotational velocity (v sin i)1.70±0.45 km/s
Age5.71±5.29 Gyr
Other designations
Anunitu, ε And, 30 Andromedae, BD+28°103, FK5 19, GC 759, HD 3546, HIP 3031, HR 163, SAO 74164, PPM 90002, LTT 10215, NLTT 2065
Database references
SIMBADdata

Epsilon Andromedae, also named Anunitu, is a star in the constellation of Andromeda. This star can be seen with the naked eye, having an apparent visual magnitude of 4.4. Based upon an annual parallax shift of 19.2 mas as seen from Earth, it is located approximately 169 light years from the Sun. The system is moving closer to the Sun with a radial velocity of −84 km/s. Its orbit in the Milky Way is highly eccentric, causing it to move rapidly relative to the Sun and its neighboring stars.

Nomenclature

Epsilon Andromedae is a Bayer designation that is Latinized from ε Andromedae, and abbreviated eps And or ε And, respectively.

In Chinese astronomy, 奎宿 (Kuí Sù), meaning Legs (asterism), refers to an asterism consisting of ε Andromedae, η Andromedae, 65 Piscium, ζ Andromedae, δ Andromedae, π Andromedae, ν Andromedae, μ Andromedae, β Andromedae, σ Piscium, τ Piscium, 91 Piscium, υ Piscium, φ Piscium, χ Piscium and ψ¹ Piscium. Consequently, the Chinese name for ε Andromedae itself is 奎宿四 (Kuí Sù sì, English: the Fourth Star of Legs.)

Anunītu is a Mesopotamian goddess, originally an epithet of Ishtar, whose constellation was visualized in Andromeda and Pisces in ancient times. The IAU Working Group on Star Names adopted the name Anunitu for this star on 15 October 2026.

Properties

This is an evolved G-type giant star with a stellar classification of G6 III Fe−3 CH1. The suffix notation indicates there is a strong underabundance of iron in the spectrum, and an overabundance of cyanogen (CN). ε Andromedae is believed to be a red clump star which is fusing helium in its core. It has about the same mass as the Sun, but has expanded to nine times the Sun's radius. The star is radiating 51 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 5,082 K.

References

  1. 1 2 3 4 5 6 Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  2. 1 2 3 4 Jennens, P. A.; Helfer, H. L. (September 1975). "A new photometric metal abundance and luminosity calibration for field G and K giants". Monthly Notices of the Royal Astronomical Society. 172 (3): 667–679. Bibcode:1975MNRAS.172..667J. doi:10.1093/mnras/172.3.667.
  3. 1 2 Puzeras, E.; et al. (October 2010). "High-resolution spectroscopic study of red clump stars in the Galaxy: iron-group elements". Monthly Notices of the Royal Astronomical Society. 408 (2): 1225–1232. arXiv:1006.3857. Bibcode:2010MNRAS.408.1225P. doi:10.1111/j.1365-2966.2010.17195.x. S2CID 44228180.
  4. 1 2 Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins catalog of revised MK types for the cooler stars". Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.
  5. 1 2 3 "eps And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved August 28, 2008.
  6. ↑ HR 163, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line August 28, 2008.
  7. 1 2 3 4 Jofré, E.; Petrucci, R.; Saffe, C.; Saker, L.; de la Villarmois, E. Artur; Chavero, C.; Gómez, M.; Mauas, P. J. D. (2015). "Stellar parameters and chemical abundances of 223 evolved stars with and without planets". Astronomy & Astrophysics. 574: A50. arXiv:1410.6422. Bibcode:2015A&A...574A..50J. doi:10.1051/0004-6361/201424474. S2CID 53666931.
  8. ↑ Takeda, Yoichi; et al. (August 2008). "Stellar Parameters and Elemental Abundances of Late-G Giants". Publications of the Astronomical Society of Japan. 60 (4): 781–802. arXiv:0805.2434. Bibcode:2008PASJ...60..781T. doi:10.1093/pasj/60.4.781. S2CID 16258166.
  9. 1 2 "IAU Catalog of Star Names". Retrieved 18 October 2026.
  10. ↑ Epsilon Andromedae Archived 2007-04-28 at the Wayback Machine, Stars, Jim Kaler. Accessed on line August 28, 2008.
  11. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 19 日 Archived 2016-03-03 at the Wayback Machine