Spectroscopic binary star in the constellation Andromeda
η Andromedae Location of η Andromedae (circled)
Observation dataEpoch J2000.0 Equinox J2000.0 (ICRS ) Constellation Andromeda Right ascension 00h 57m 12.400s [ 1] Declination +23° 25′ 03.54″[ 1] Apparent magnitude (V)4.403[ 2] Characteristics Spectral type G8III-IV + G8III-IV [ 3] U−Bcolor index +0.69[ 4] B−Vcolor index +0.94[ 4] R−Icolor index +0.48[ 4] Astrometry η And A Radial velocity (Rv )−10.30± 0.29[ 5] km/s Proper motion (μ)RA: −43.008mas /yr [ 1] Dec.: −45.254mas /yr [ 1] Parallax (π)12.5624± 0.2525 mas [ 1] Distance 260 ± 5 ly pc ) Absolute magnitude (MV )0.52± 0.06[ 3] η And B Absolute magnitude (MV )1.07± 0.07[ 3] Orbit [ 3] Period (P)± 0.01 dSemi-major axis (a)± 0.03 masEccentricity (e)0.006± 0.002 Inclination (i)30.5± 0.4° Longitude of the node (Ω)69.4± 0.5° Periastron epoch (T)013 ± 1 MJD Argument of periastron (ω)215± 4° Details η And A Mass 2.6± 0.35[ 6] M ☉ Radius 10.7[ 7] R ☉ Luminosity (bolometric) 65± 3[ 3] L ☉ Surface gravity (log g )2.8[ 3] cgs Temperature 4,900[ 3] K Age 800[citation needed Myr η And B Mass 2.3± 0.31[ 6] M ☉ Radius 8.6[ 7] R ☉ Luminosity (bolometric) 39± 3[ 3] L ☉ Surface gravity (log g )3.0[ 3] cgs Temperature 4,900[ 3] K Other designations Kui,η Andromedae, η And, Eta And ,38 Andromedae, 38 And ,BD +22°153FK5 2060GC 1136HD 5516HIP 4463HR 271SAO 74388PPM 90327CCDM J00572+2325AWDS 00572+2325A/Aa[ 2] [ 8] [ 9] Database references SIMBAD data
Eta Andromedae , also namedKui ,[ 10] spectroscopic binary star system in the northernconstellation ofAndromeda . It consists of twoG-type evolved stars orbiting each other with a period of 115.7 days and has an overallapparent visual magnitude of approximately 4.403.[ 2] [ 3] parallax measurements, this system is located at a distance of approximately 260 light years from theSun .[ 1] radial velocity of −10.30 km/s.[ 5]
η Andromedae system as seen from earth orbit,M 33 in background This star was discovered to be a double-linedspectroscopic binary in a series ofspectra taken in 1899 and 1900.[ 11] [ 12] radial velocity of a star towards or away from the viewer, such a computation does not determine allorbital elements . In observations made from 1990 to 1992, Eta Andromedae was resolvedinterferometrically by theMark III Stellar Interferometer atMount Wilson Observatory ,California ,United States . This allowed a more complete orbit to be computed and, in 1993, published.[ 3]
The primary component has 2.6[ 6] mass of the Sun and 10.7[ 7] [ 3] photosphere at aneffective temperature of 4,900 K.[ 3] [ 6] [ 7] [ 3] [ 3]
Eta Andromedae has a visualcompanion star ofapparent visual magnitude 11.5, BD+22°153B, visible 129.2arcseconds away.[ 9]
InChinese ,奎宿 Kuí Sù Legs (asterism)ζ Andromedae ,ε Andromedae ,δ Andromedae ,π Andromedae ,ν Andromedae ,μ Andromedae ,β Andromedae ,σ Piscium ,τ Piscium , 91 Piscium,υ Piscium ,φ Piscium ,χ Piscium andψ¹ Piscium . Consequently, theChinese name for η Andromedae itself is奎宿一 Kuí Sù yī the First Star of Legs .)[ 13] IAU Working Group on Star Names approved the name Kui for Eta Andromedae A, on 6 April 2025 and it is now so entered in the IAU Catalog of Star Names.[ 10]
^a b c d e 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 atVizieR .^a b c "* eta And" .SIMBAD Centre de données astronomiques de Strasbourg . RetrievedAugust 23, 2008 .^a b c d e f g h i j k l m n o p Hummel, C. A.; et al. (December 1993). "The spectroscopic binary eta Andromedae: Determination of the orbit by optical interferometry".Astronomical Journal .106 (6):2486– 2492.Bibcode :1993AJ....106.2486H .doi :10.1086/116816 . ^a b c HR 271 , database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr.,CDS IDV/50 . Accessed on line August 23, 2008.^a b Karataș, Yüksel; et al. (2004)."Kinematics of chromospherically active binaries and evidence of an orbital period decrease in binary evolution" .Monthly Notices of the Royal Astronomical Society .349 (3):1069– 1092.arXiv :astro-ph/0404219 Bibcode :2004MNRAS.349.1069K .doi :10.1111/j.1365-2966.2004.07588.x S2CID 15290475 . ^a b c d Pourbaix, D. (August 2000). "Resolved double-lined spectroscopic binaries: A neglected source of hypothesis-free parallaxes and stellar masses".Astronomy and Astrophysics Supplement .145 (2):215– 222.Bibcode :2000A&AS..145..215P .doi :10.1051/aas:2000237 . ^a b c d Eggleton, Peter P.; Yakut, Kadri (July 2017)."Models for 60 double-lined binaries containing giants" .Monthly Notices of the Royal Astronomical Society .468 (3):3533– 3556.arXiv :1611.05041 Bibcode :2017MNRAS.468.3533E .doi :10.1093/mnras/stx598 ^ Entry 00572+2325, discoverer code MKT 2, components Aa,The Washington Double Star Catalog Archived April 12, 2008, at theWayback Machine ,United States Naval Observatory . Accessed on line August 27, 2008. ^a b Entry 00572+2325, discoverer code FOX 116, components AB,The Washington Double Star Catalog Archived April 12, 2008, at theWayback Machine ,United States Naval Observatory . Accessed on line August 23, 2008. ^a b "IAU Catalog of Star Names" . Retrieved6 April 2025 .^ Campbell, W. W.; Wright, W. H. (November 1900). "A list of nine stars whose velocities in the line of sight are variable".Astrophysical Journal .12 :254– 257.Bibcode :1900ApJ....12..254C .doi :10.1086/140765 . ^ Gordon, Katherine C. (January 1946). "The Spectroscopic Binary η Andromedae".Astrophysical Journal .103 :13– 15.Bibcode :1946ApJ...103...13G .doi :10.1086/144783 . ^ (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 theWayback Machine
