Tau Cassiopeiae

Tau Cassiopeiae (τ Cassiopeiae) is a solitary,[10] orange hued star in the northern constellation of Cassiopeia. It is bright enough to be seen with the naked eye, having an apparent visual magnitude of +4.86.[2] Based upon an annual parallax shift of 18.75 mas as seen from Earth,[1] this system is located about 174 light years from the Sun.

The spectrum of this star indicates it is an evolved, K-type giant star with a stellar classification of K1 IIIa.[3] It is a suspected variable star of unknown type.[4][11] Tau Cassiopeiae is 3.9[7] billion years old with about 1.44[7] times the mass of the Sun and 10[5] times the Sun's radius. It is radiating 40[7] times the Sun's luminosity from its expanded photosphere at an effective temperature of around 4,617 K.[7]

Tau Cassiopeiae
Tau cassiopeiae diagram

Map of the Bayer-designated stars in Cassiopeia. Tau Cassiopeiae is circled.
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Cassiopeia
Right ascension 00h 55m 00.15523s[1]
Declination +58° 58′ 21.7108″[1]
Apparent magnitude (V) +4.86[2]
Spectral type K1 IIIa[3]
U−B color index +1.05[2]
B−V color index +1.11[2]
Variable type Suspected[4]
Radial velocity (Rv)−20.48±0.31[5] km/s
Proper motion (μ) RA: +60.81±0.19[1] mas/yr
Dec.: +56.47±0.17[1] mas/yr
Parallax (π)18.75 ± 0.20[1] mas
Distance174 ± 2 ly
(53.3 ± 0.6 pc)
Absolute magnitude (MV)1.269[6]
Mass1.44[7] M
Radius10[5] R
Luminosity40[7] L
Surface gravity (log g)2.50±0.09[8] cgs
Temperature4,617±77[7] K
Metallicity [Fe/H]+0.06±0.06[8] dex
Rotational velocity (v sin i)5.9[5] km/s
Age3.90[7] Gyr
Other designations
τ Cas, 5 Cas, BD+57° 2804, FK5 3909, HD 223165, HIP 117301, HR 9008, SAO 35763[9]
Database references


In Chinese, 螣蛇 (Téng Shé), meaning Flying Serpent, refers to an asterism consisting of τ Cassiopeiae, α Lacertae, 4 Lacertae, π2 Cygni, π1 Cygni, HD 206267, ε Cephei, β Lacertae, σ Cassiopeiae, ρ Cassiopeiae, AR Cassiopeiae, 9 Lacertae, 3 Andromedae, 7 Andromedae, 8 Andromedae, λ Andromedae, κ Andromedae, ι Andromedae, and ψ Andromedae. Consequently, τ Cassiopeiae itself is known as 螣蛇十三 (Téng Shé shísān, English: the Thirteenth Star of Flying Serpent)[12]


  1. ^ a b c d e f van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
  2. ^ a b c d Argue, A. N. (1966), "UBV photometry of 550 F, G and K type stars", Monthly Notices of the Royal Astronomical Society, 133: 475, Bibcode:1966MNRAS.133..475A, doi:10.1093/mnras/133.4.475.
  3. ^ a b Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
  4. ^ a b Halbedel, E. M. (February 1993), "tau Cas: a Variable Star after All?", Information Bulletin on Variable Stars (3851): 1, Bibcode:1993IBVS.3851....1H.
  5. ^ a b c d Massarotti, Alessandro; et al. (January 2008), "Rotational and radial velocities for a sample of 761 HIPPARCOS giants and the role of binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209
  6. ^ Soubiran, C.; et al. (March 2008), "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants", Astronomy and Astrophysics, 480 (1): 91–101, arXiv:0712.1370Freely accessible, Bibcode:2008A&A...480...91S, doi:10.1051/0004-6361:20078788.
  7. ^ a b c d e f g h Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 88, arXiv:1507.01466Freely accessible, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88
  8. ^ a b Wu, Yue; et al. (2010), "Coudé-feed stellar spectral library – atmospheric parameters", Astronomy & Astrophysics, 525: A71, arXiv:1009.1491Freely accessible, Bibcode:2011A&A...525A..71W, doi:10.1051/0004-6361/201015014.
  9. ^ "tau Cas". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-08-30.
  10. ^ 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, arXiv:0806.2878Freely accessible, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x.
  11. ^ Halbedel, E. M. (November 1989), "Another Opinion on the Variability of tau Cas", Information Bulletin on Variable Stars (3394): 1, Bibcode:1989IBVS.3394....1H.
  12. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 7 日

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