Zeta Andromedae

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ζ Andromedae
Template:Location mark
Location of ζ Andromedae
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Andromeda
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) Template:Val[2]
Characteristics
Spectral type K1III + KV[3]
U−B Template:Engvar +0.90[4]
B−V Template:Engvar +1.12[4]
R−I Template:Engvar +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]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)+0.14[3]
Orbit[3]
Period (P)17.769426 days
Semi-major axis (a)Template:Val
Eccentricity (e)0.0
Inclination (i)65±5°
Details
Aa
Mass2.6±0.4[3] Template:Solar mass
Radius15.9±0.8[6] Template:Solar radius
Luminosity95.5[3] Template:Solar luminosity
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] Template:Solar mass
Metallicity [Fe/H]{{{metal_fe2}}} dex
Other designations
Template:Odlist[8]
Database references
SIMBADdata

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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 Template:Val 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

File:Sidney Hall - Urania's Mirror - Gloria Frederici, Andromeda, and Triangula.png
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, Script error: No such module "Lang". (Script error: No such module "Lang".), 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 Script error: No such module "Lang". (Script error: No such module "Lang"., Template:Langx).[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

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

The system is a spectroscopic binary whose Template:Abbreviation 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 Template:Val
Axis InclinationTemplate:Efn Template:Val
Pole angleTemplate:Efn Template:Val

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

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 Template:Val shares a common proper motion and a similar parallax.[15]

Template:Componentbox begin

Template:Componentbox component Template:Componentbox component Template:Componentbox component Template:Componentbox end

Notes

Template:Notes

References

Template:Reflist

External links

Template:Stars of Andromeda Template:Sky

  1. ↑ a b c d Cite error: Invalid <ref> tag; no text was provided for refs named GaiaEDR3
  2. ↑ a b c Cite error: Invalid <ref> tag; no text was provided for refs named gcvs1
  3. ↑ a b c d e f g h i j k Cite error: Invalid <ref> tag; no text was provided for refs named kovari
  4. ↑ a b c d Cite error: Invalid <ref> tag; no text was provided for refs named bsc2
  5. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named karatas
  6. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named korhonen
  7. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named aar17_3_251
  8. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named SIMBAD
  9. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named IAU-CSN-new
  10. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named aeea
  11. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Kovari
  12. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named roettenbacher
  13. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named dr3d
  14. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named dr3b
  15. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named dr3c
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