Zeta Cassiopeiae

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ζ Cassiopeiae
Cassiopeia constellation map.svg
ζ Cas is found just below α Cas
Observation data
Epoch J2000      Equinox J2000
Constellation Cassiopeia
Right ascension 00h 36m 58.28419s[1]
Declination +53° 53′ 48.8673″[1]
Apparent magnitude (V) 3.666[2]
Spectral type B2IV[3]
U−B color index –0.89[4]
B−V color index –0.19[4]
Variable type SPB[5]
Radial velocity (Rv) 2.0[2] km/s
Proper motion (μ) RA: 17.38[1] mas/yr
Dec.: –9.86[1] mas/yr
Parallax (π) 5.50 ± 0.16[1] mas
Distance 590 ± 20 ly
(182 ± 5 pc)
Absolute magnitude (MV) –2.63
Mass 8.4[6] M
Radius 5.8[7] R
Luminosity 6,400[5] L
Surface gravity (log g) 3.92[8] cgs
Temperature 22,180[8] K
Metallicity [Fe/H] –0.23[8] dex
Rotational velocity (v sin i) 2.0[9] km/s
Age 2.0×107[5] years
Other designations
17 Cassiopeiae, HR 153, HD 3360, BD+53°105, FK5 17, HIP 2920, SAO 21566, GC 727.[2]
Database references

Zeta Cassiopeiae (ζ Cas, ζ Cassiopeiae) is a star in the constellation Cassiopeia. It has a blue-white hue and is classified as a B-type subgiant with an apparent magnitude of +3.67. It is approximately 590 light years from Earth.[1]

ζ Cas is a member of an unusual group of variable stars known as "Slowly Pulsating B" (SPB) stars.[10] It shows a pulsation frequency of 0.64 per day (or once every 1.56 days) and displays a weak magnetic field with a strength of roughly 3.35 × 10−2 T, which varies with a period of 5.37 days.[11] This likely matches the rotation rate of the star, which, when combined with the low projected rotational velocity, indicates the star may be seen nearly pole-on. Zeta Cassiopeiae is a candidate magnetic Bp star that shows an overabundance of helium. The star contains a randomly oriented fossil magnetic field, which impacts the outflow of the stellar wind. Collisions between streams from this stellar wind creates a shock front, with cooling particles settling toward a co-rotating disk.[12]

Chinese name[edit]

In Chinese astronomy, Zeta Cassiopeiae is called 附路, Pinyin: Fùlù, meaning Auxiliary Road, because this star is marking itself and stand alone in Auxiliary Road asterism, Legs (mansion) (see : Chinese constellation).[13] 附路 (Fùlù) is westernized into Foo Loo, but the name Foo Loo was designated not only for Zeta Cassiopeiae, but also for η Cassiopeiae (Achird) by R.H. Allen, with the meaning is "a by-path" [14]

See also[edit]


  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, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 
  2. ^ a b c "NSV 225 -- Pulsating variable Star", SIMBAD (Centre de Données astronomiques de Strasbourg), retrieved 2010-02-22 
  3. ^ Morgan, W. W.; Keenan, P. C. (1973), "Spectral Classification", Annual Review of Astronomy and Astrophysics 11: 29, Bibcode:1973ARA&A..11...29M, doi:10.1146/annurev.aa.11.090173.000333 
  4. ^ a b 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 
  5. ^ a b c Kaler, James B. (Jim), ZETA CAS (Zeta Cassiopeiae), University of Illinois, retrieved 2010-02-22 
  6. ^ Venn, K. A.; Lambert, D. L.; Lemke, M. (March 1996), "The abundance of boron in evolved A- and B-type stars.", Astronomy and Astrophysics 307: 849–859, arXiv:astro-ph/9508001, Bibcode:1996A&A...307..849V 
  7. ^ Underhill, A. B. et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society 189: 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601 
  8. ^ a b c Gies, Douglas R.; Lambert, David L. (March 1992), "Carbon, nitrogen, and oxygen abundances in early B-type stars", Astrophysical Journal, Part 1 387: 673–700, Bibcode:1992ApJ...387..673G, doi:10.1086/171116 
  9. ^ Wielen, R. et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions (35), Astronomisches Rechen-Institut Heidelberg, Bibcode:1999VeARI..35....1W 
  10. ^ Neiner, C. et al. (2003), "Discovery of a magnetic field in the Slowly Pulsating B star zeta Cassiopeiae", Astronomy and Astrophysics 406 (3): 1019–1031, Bibcode:2003A&A...406.1019N, doi:10.1051/0004-6361:2003074 
  11. ^ De Cat, P. (June 2007), "Observational Asteroseismology of slowly pulsating B stars", Communications in Astroseismology 150: 167–174, Bibcode:2007CoAst.150..167D, doi:10.1553/cia150s167 
  12. ^ Smith, M. A.; Bohlender, D. A. (May 2007), "Variations of the ultraviolet resonance lines of the B2 IV-V star ζ Cassiopeiae", Astronomy and Astrophysics 466 (2): 675–682, arXiv:astro-ph/0702461, Bibcode:2007A&A...466..675S, doi:10.1051/0004-6361:20066639 
  13. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 9 日
  14. ^ Richard Hinckley Allen: Star Names — Their Lore and Meaning: Cassiopeia