Zeta Cassiopeiae

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ζ Cassiopeiae
Cassiopeia constellation map.svg
ζ Cassiopeiae is found just south of the W asterism
Observation data
Epoch J2000      Equinox J2000
Constellation Cassiopeia
Right ascension 00h 36m 58.28419s[1]
Declination +53° 53′ 48.8673″[1]
Apparent magnitude (V) 3.66[2] (3.59 - 3.68[3])
Spectral type B2IV[4]
U−B color index –0.89[5]
B−V color index –0.19[5]
Variable type SPB[3]
Radial velocity (Rv) 2.0[3] 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) –2.8[6]
Mass 8.3[3] M
Radius 5.9[3] R
Luminosity 5,500[3] L
Surface gravity (log g) 3.81[3] cgs
Temperature 20,426[3] K
Metallicity [Fe/H] –0.23[7] dex
Rotation 5.37045[3]
Rotational velocity (v sin i) 17 ± 3[3] km/s
Other designations
17 Cassiopeiae, HR 153, HD 3360, BD+53°105, FK5 17, HIP 2920, SAO 21566, GC 727[8]
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 +3.66. It is approximately 590 light years from Earth.


Cassiopeia starfield

ζ Cas is B2 subgiant, indicating that it has exhausted its core hydrogen and started to evolve away from the main sequence. It has a temperature of over 20,000 K, is about eight times the mass of the sun, and is 5,500 times as luminous.


ζ Cas is a probable member of an unusual group of variable stars known as "Slowly Pulsating B" (SPB) stars.[9] 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.[10] 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.[11]

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).[12] 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" [13]


  1. ^ a b c d e 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. ^ Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D. 
  3. ^ a b c d e f g h i j Neiner, C.; Geers, V. C.; Henrichs, H. F.; Floquet, M.; Frémat, Y.; Hubert, A.-M.; Preuss, O.; Wiersema, K. (2003). "Discovery of a magnetic field in the Slowly Pulsating B star zeta Cassiopeiae". Astronomy and Astrophysics. 406 (3): 1019. Bibcode:2003A&A...406.1019N. doi:10.1051/0004-6361:20030742. 
  4. ^ 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 
  5. ^ a b Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J 
  6. ^ Jaschek, C.; Gomez, A. E. (1998). "The absolute magnitude of the early type MK standards from HIPPARCOS parallaxes". Astronomy and Astrophysics. 330: 619. Bibcode:1998A&A...330..619J. 
  7. ^ 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 
  8. ^ "Zeta Cas -- Pulsating variable Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2010-02-22 
  9. ^ 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:10.1051/0004-6361:20030742 
  10. ^ 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 
  11. ^ 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, Bibcode:2007A&A...466..675S, arXiv:astro-ph/0702461Freely accessible, doi:10.1051/0004-6361:20066639 
  12. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 9 日
  13. ^ Richard Hinckley Allen: Star Names — Their Lore and Meaning: Cassiopeia