Eta Andromedae

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Template:Short description

η Andromedae
Template:Location mark
Location of η Andromedae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Andromeda
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) 4.403[2]
Characteristics
Spectral type G8III-IV + G8III-IV[3]
U−B Template:Engvar +0.69[4]
B−V Template:Engvar +0.94[4]
R−I Template:Engvar +0.48[4]
Astrometry
η And A
Radial velocity (Rv)−10.30±0.29[5] km/s
Proper motion (μ) RA: −43.008 mas/yr[1]
Dec.: −45.254 mas/yr[1]
Parallax (π)12.5624±0.2525 mas[1]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)0.52±0.06[3]
η And B
Absolute magnitude (MV)1.07±0.07[3]
Orbit[3]
Period (P)Script error: No such module "val".
Semi-major axis (a)Script error: No such module "val".
Eccentricity (e)0.006±0.002
Inclination (i)30.5±0.4°
Longitude of the node (Ω)69.4±0.5°
Periastron epoch (T)Script error: No such module "val".
Argument of periastron (ω)
(secondary)		215±4°
Details
η And A
Mass2.6±0.35[6] Template:Solar mass
Radius10.7[7] Template:Solar radius
Luminosity (bolometric)65±3[3] Template:Solar luminosity
Surface gravity (log g)2.8[3] cgs
Temperature4,900[3] K
Age800Script error: No such module "Unsubst". Myr
η And B
Mass2.3±0.31[6] Template:Solar mass
Radius8.6[7] Template:Solar radius
Luminosity (bolometric)39±3[3] Template:Solar luminosity
Surface gravity (log g)3.0[3] cgs
Temperature4,900[3] K
Metallicity [Fe/H]{{{metal_fe2}}} dex
Other designations
Template:Odlist[2][8][9]
Database references
SIMBADdata

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Eta Andromedae, also named Kui,[10] is a spectroscopic binary star system in the northern constellation of Andromeda. It consists of two G-type evolved stars orbiting each other with a period of 115.7 days and has an overall apparent visual magnitude of approximately 4.403.[2][3] Based on parallax measurements, this system is located at a distance of approximately 260 light years from the Sun.[1] But it is drawing closer with a heliocentric radial velocity of −10.30 km/s.[5]

File:Eta And AB Orbit.jpg
η Andromedae system as seen from earth orbit, M 33 in background

This star was discovered to be a double-lined spectroscopic binary in a series of spectra taken in 1899 and 1900.[11] Its orbit was computed in 1946 from spectroscopic observations.[12] Because spectroscopy only reveals the radial velocity of a star towards or away from the viewer, such a computation does not determine all orbital elements. In observations made from 1990 to 1992, Eta Andromedae was resolved interferometrically by the Mark III Stellar Interferometer at Mount 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] times the mass of the Sun and 10.7[7] times the Sun's radius. It is radiating 65[3] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,900 K.[3] The fainter secondary member has 2.3[6] times the mass and 8.6[7] times the radius of the Sun. It radiates 39[3] times the luminosity of the Sun at a temperature of 4,900 K.[3]

Eta Andromedae has a visual companion star of apparent visual magnitude 11.5, BD+22°153B, visible 129.2 arcseconds away.[9]

Naming

In Chinese, Script error: No such module "Lang". (Script error: No such module "Lang".), meaning Legs (asterism), refers to an asterism consisting of η Andromedae, 65 Piscium, 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 and ψ¹ Piscium. Consequently, the Chinese name for η Andromedae itself is Script error: No such module "Lang". (Script error: No such module "Lang"., Template:Langx.)[13] The IAU Working Group on Star Names approved the name Kui for this star on 6 April 2025 and it is now so entered in the IAU Catalog of Star Names.[10]

References

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  1. ↑ a b c d e Template:Cite Gaia EDR3
  2. ↑ a b c Template:Cite simbad
  3. ↑ a b c d e f g h i j k l m n o p Script error: No such module "Citation/CS1".
  4. ↑ a b c HR 271, 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 23, 2008.
  5. ↑ a b Script error: No such module "Citation/CS1".
  6. ↑ a b c d Script error: No such module "Citation/CS1". See table 2.
  7. ↑ a b c d Script error: No such module "Citation/CS1".
  8. ↑ Entry 00572+2325, discoverer code MKT 2, components Aa, The Washington Double Star Catalog Template:Webarchive, United States Naval Observatory. Accessed on line August 27, 2008.
  9. ↑ a b Entry 00572+2325, discoverer code FOX 116, components AB, The Washington Double Star Catalog Template:Webarchive, United States Naval Observatory. Accessed on line August 23, 2008.
  10. ↑ a b Script error: No such module "citation/CS1".
  11. ↑ Script error: No such module "Citation/CS1".
  12. ↑ Script error: No such module "Citation/CS1".
  13. ↑ Template:In lang AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 19 日 Template:Webarchive

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External links

Template:Stars of Andromeda Template:Sky

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