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Zeta Andromedae

Coordinates: Sky map 00h 47m 20.3254s, +24° 16′ 01.841″
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(Redirected from Ζ Andromedae)
Not to be confused with Z Andromedae.
ζ Andromedae
Location of ζ Andromedae
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Andromeda
Right ascension 00h 47m 20.326s[1]
Declination +24° 16′ 01.84″[1]
Apparent magnitude (V) 3.92 to 4.14[2]
Characteristics
Spectral type K1III + KV[3]
U−B color index +0.90[4]
B−V color index +1.12[4]
R−I color index +0.59[4]
Variable type ELL/RS[2]
Astrometry
Radial velocity (Rv)−24.43±0.1[5] km/s
Proper motion (μ) RA: −101.068 mas/yr[1]
Dec.: −80.276 mas/yr[1]
Parallax (π)18.0083±0.1604 mas[1]
Distance181 ± 2 ly
(55.5 ± 0.5 pc)
Absolute magnitude (MV)+0.14[3]
Orbit[3]
Period (P)17.769426 days
Semi-major axis (a)2.7 R☉
Eccentricity (e)0.0
Inclination (i)65±5°
Details
Aa
Mass2.6±0.4[3] M☉
Radius15.9±0.8[6] R☉
Luminosity95.5[3] L☉
Surface gravity (log g)2.8[3] cgs
Temperature4,665±140[6] K
Metallicity [Fe/H]−0.30[3] dex
Rotation17.77 days[7]
Rotational velocity (v sin i)41.4±0.2[3] km/s
Ab
Mass0.75[3] M☉
Other designations
ζ And, Zeta Andromedae, Zet And, 34 Andromedae, 34 And, BD+23 106, FK5 27, GC 940, HD 4502, HIP 3693, HR 215, SAO 74267, PPM 90149, CCDM J00473+2416A, WDS 00473+2416A[8]
Database references
SIMBADdata

Zeta Andromedae, also named Shimu,[9] is a binary star system in the northern constellation Andromeda. It is visible to the naked eye with an apparent visual magnitude that varies from 3.92 to 4.14 over the course of its 17.7 day orbit.[2] Based on parallax measurements, it is located at a distance of approximately 181 light-years from the Sun. The system is drifting closer with a heliocentric radial velocity of −24.4 km/s.[5]

Naming

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Sidney Hall - Urania's Mirror - Gloria Frederici, Andromeda, and Triangula (north is to the left)

The star's location is in the northern constellation Andromeda, in which it is the second-most southerly of the stars in this often drawn characteristic shape representing the mythical princess asterism, after η Andromedae.

Zeta Andromedae (Zeta And, ζ Andromedae, ζ And) is the star's Bayer designation. It also has the Flamsteed designation 34 Andromedae and multiple other designations in stellar catalogues.

In Chinese, 奎宿 (Kuí Sù), meaning Legs (asterism), refers to an asterism consisting of ζ Andromedae, η Andromedae, 65 Piscium, 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 ζ Andromedae itself is 奎宿二 (Kuí Sù èr, English: the Second Star of Legs).[10]

An older Chinese name is Tian Shi Mu, The Eye of the Celestial Pig. Based on this, the IAU Working Group on Star Names approved the name Shimu for this star on 16 March 2025 and it is now so entered in the IAU Catalog of Star Names.[9]

System

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A visual band light curve for Zeta Andromedae, adapted from Kővári et al. (2006)[11]

The system is a spectroscopic binary whose primary is classified as an orange K-type giant with a mean apparent magnitude of +4.08. Due to brightness changes caused by the ellipsoidal shape of that object, the system is also an RS Canum Venaticorum-type variable star. It is a magnetically active star with a brightness that varies from magnitude +3.92 to +4.14 over a period of 17.77 days, and its spectrum shows strong and variable Ca II H and K lines. The orbital period of the binary is 17.77 days.[3]

The primary component of this binary system, Zeta Andromedae Aa, is one of the few stars who has been resolved using Doppler imaging and long-baseline infrared interferometry. With resolved images astronomers can recover additional information about this star.

Additional star parameters[12]
Parameter Value
Oblateness 1.060±0.011
Polar radius 15.0±0.8 R☉
Axis Inclination[a] 70.0°±2.8°
Pole angle[b] 126°±1.9°

Resolved images also allowed observation of starspots (the analogue to sunspots), on this star, and their asymmetric distribution showed that the magnetic field of the star is generated by a mechanism different from the solar dynamo.[12] A Sun-like differential rotation of the star was observed instead.[3]

Visual companions

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The WDS notes three visual companions to the eclipsing binary (Aa and Ab, forming binary A).[4] The parallax of the D star has been measured by Gaia proving its distance to be much greater than Zeta Andromedae, probably a distant red giant.[13] The closest companion, B, is likewise a background object.[14] The companion C at 97″ shares a common proper motion and a similar parallax.[15]

Multiple/double star designation: WDS 00473+2416[16]
Component Primary Right
ascension (α)
Equinox J2000.0		 Declination (δ)
Equinox J2000.0		 Epoch of
observed
separation		 Angular
distance
from
primary		 Position
angle
(relative
to primary)		 Apparent
magnitude
(V)		 Database
reference
B A 00h 47m 20.2s+24° 16′ 33″ 1959 32.6″ 0° 15.3
C A 00h 47m 15.2s+24° 15′ 03″ 1997 97.0″ 231° 13.6
D A 00h 47m 09.0s+24° 15′ 33″ 2006 155.5″ 260° 10.80 SIMBAD

Notes

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  1. ^ Azimuthal angle between the rotational axis and our line of sight
  2. ^ Longitudinal angle between the north pole and the East direction

References

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  1. ^ a b c d 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. ^ a b c zet And, database entry, The combined table of GCVS Vols I-III and NL 67-78 with improved coordinates, General Catalogue of Variable Stars Archived 2017-06-20 at the Wayback Machine, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line August 29, 2008.
  3. ^ a b c d e f g h i j k Kővári, Zs.; Bartus, J.; Strassmeier, K. G.; Oláh, K.; Weber, M.; Rice, J. B.; Washuettl, A. (2007). "Doppler imaging of stellar surface structure. XXIII. The ellipsoidal K giant binary ζ Andromedae". Astronomy and Astrophysics. 463 (3): 1071. Bibcode:2007A&A...463.1071K. doi:10.1051/0004-6361:20065982.
  4. ^ a b c d HR 215, 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 29, 2008.
  5. ^ a b Karataș, Yüksel; Bilir, Selçuk; Eker, Zeki; Demircan, Osman; Liebert, James; Hawley, Suzanne L.; Fraser, Oliver J.; Covey, Kevin R.; Lowrance, Patrick; Kirkpatrick, J. Davy; Burgasser, Adam J. (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.
  6. ^ a b Korhonen, H.; Wittkowski, M.; Kovári, Zs.; Granzer, Th.; Hackman, T.; Strassmeier, K. G. (2010). "Ellipsoidal primary of the RS CVn binary ζ Andromedae . Investigation using high-resolution spectroscopy and optical interferometry". Astronomy and Astrophysics. 515: A14. arXiv:1002.4201. Bibcode:2010A&A...515A..14K. doi:10.1051/0004-6361/200913736. S2CID 118683792.
  7. ^ Strassmeier, Klaus G. (September 2009), "Starspots", The Astronomy and Astrophysics Review, 17 (3): 251–308, Bibcode:2009A&ARv..17..251S, doi:10.1007/s00159-009-0020-6
  8. ^ "zet And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2025-03-21.
  9. ^ a b "IAU Catalog of Star Names". Retrieved 16 March 2025.
  10. ^ (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
  11. ^ Kővári, Zsolt; Oláh, Katalin; Bartus, János; Strassmeier, Klaus G.; Granzer, Thomas (August 2006). "Spot Modelling of ζ Andromedae". Astrophysics and Space Science. 304 (1–4): 55–57. Bibcode:2006Ap&SS.304...55K. doi:10.1007/s10509-006-9073-4. S2CID 119574869. Retrieved 9 August 2022.
  12. ^ a b Roettenbacher, R.M.; Monnier, J.D.; Korhonen, H.; Aarnio, A.N.; Baron, F.; Che, X.; Harmon, R.O.; Kővári, Zs.; Kraus, S.; Schaefer, G.H.; Torres, G.; Zhao, M.; Ten Brummelaar, T.A.; Sturmann, J.; Sturmann, L. (2016). "No Sun-like dynamo on the active star ζ Andromedae from starspot asymmetry". Nature. 533 (7602): 217–220. arXiv:1709.10107. Bibcode:2016Natur.533..217R. doi:10.1038/nature17444. PMID 27144357. S2CID 4466687.
  13. ^ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  14. ^ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  15. ^ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  16. ^ Entry 00473+2416, The Washington Double Star Catalog Archived April 12, 2008, at the Wayback Machine, United States Naval Observatory. Accessed on line August 29, 2008.
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