Theta Andromedae

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Theta Andromedae
Diagram showing star positions and boundaries of the Andromeda constellation and its surroundings
Cercle rouge 100%.svg

Location of θ Sagittarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension 00h 17m 05.49885s[1]
Declination +38° 40′ 53.8902″[1]
Apparent magnitude (V) 4.61[2]
Spectral type A2 V[3]
U−B color index +0.05[2]
B−V color index +0.06[2]
Radial velocity (Rv) 0.9[4] km/s
Proper motion (μ) RA: –49.35[1] mas/yr
Dec.: -17.65[1] mas/yr
Parallax (π) 10.56 ± 0.96[1] mas
Distance 310 ± 30 ly
(95 ± 9 pc)
Period (P) 1033+91
Semi-major axis (a) 25+32
Eccentricity (e) 0.95+0.04
Inclination (i) 69+8
Longitude of the node (Ω) 263+50
Periastron epoch (T) 238+343
Argument of periastron (ω)
Surface gravity (log g) 3.95[6] cgs
Temperature 8960[6] K
Metallicity [Fe/H] +0.14[6] dex
Rotational velocity (v sin i) 102[7] km/s
Other designations
24 Andromedae, BD+37°34, HD 1280, HIP 1366, HR 63, SAO 53777.
Database references

Theta Andromedae (θ And, θ Andromedae) is the Bayer designation for a binary star in the constellation Andromeda. It is approximately 310 light-years (95 parsecs) from Earth,[1] with a visual magnitude of 4.6.[2] On the Bortle Dark-Sky Scale, this makes it visible to the naked eye from outside urban regions.

Theta Andromedae is a white A-type main sequence dwarf with an apparent magnitude of +4.61. It appears to be a binary star with a massive, possibly A-type secondary orbiting at a distance of around 1 astronomical unit.[5] A fainter companion is separated from Theta Andromedae by 0.06 arcseconds.[8]


In Chinese, 天廄 (Tiān Jiù), meaning Celestial Stable, refers to an asterism consisting of θ Andromedae, ρ Andromedae and σ Andromedae. Consequently, θ Andromedae itself is known as 天廄一 (Tiān Jiù yī, English: the First Star of Celestial Stable.)[9]


  1. ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752Freely accessible, doi:10.1051/0004-6361:20078357 
  2. ^ a b c d Johnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99). Bibcode:1966CoLPL...4...99J. 
  3. ^ Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819 
  4. ^ Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick, Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, University of Toronto: International Astronomical Union, Bibcode:1967IAUS...30...57E 
  5. ^ a b Goldin, A.; Makarov, V. V. (September 2006), "Unconstrained Astrometric Orbits for Hipparcos Stars with Stochastic Solutions", The Astrophysical Journal Supplement Series, 166 (1): 341–350, Bibcode:2006ApJS..166..341G, arXiv:astro-ph/0606293Freely accessible, doi:10.1086/505939 
  6. ^ a b c Hill, G. M. (February 1995), "Compositional differences among the A-type stars. 2: Spectrum synthesis up to V sin i = 110 km/s", Astronomy and Astrophysics, 294 (2): 536–546, Bibcode:1995A&A...294..536H 
  7. ^ Royer, F.; Zorec, J.; Gómez, A. E. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, Bibcode:2007A&A...463..671R, arXiv:astro-ph/0610785Freely accessible, doi:10.1051/0004-6361:20065224 
  8. ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869–879. Bibcode:2008MNRAS.389..869E. arXiv:0806.2878Freely accessible. doi:10.1111/j.1365-2966.2008.13596.x. 
  9. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 18 日

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