Article · Wikipedia archive · Last revised Jul 19, 2026

Phi Cassiopeiae

Phi Cassiopeiae is a multiple star system in the northern constellation of Cassiopeia. Its name is a Bayer designation that is Latinized from φ Cassiopeiae, and abbreviated Phi Cas or φ Cas. With a combined apparent magnitude of +4.95, it is visible to the naked eye. The two brightest components are A and C, sometimes called φ1 and φ2 Cas. φ Cas A is an F0 bright supergiant of magnitude 4.95 and φ Cas C is a 7.08 magnitude B6 supergiant at 134".

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Jul 19, 2026
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φ Cassiopeiae
Location of φ Cassiopeiae (circled)
Observation data
Epoch J2000.0      Equinox ICRS
Constellation Cassiopeia1
A
Right ascension 01h 20m 04.916s2
Declination +58° 13′ 53.81″2
Apparent magnitude (V) +5.113
C
Right ascension 01h 19m 51.736s4
Declination +58° 11′ 29.32″4
Apparent magnitude (V) +7.083
Characteristics
A
Spectral type F0Ia3
U−B color index +0.495
B−V color index +0.685
C
Spectral type B6Ib3
U−B color index −0.375
B−V color index +0.415
Astrometry
A
Radial velocity (Rv)−28.396 km/s
Proper motion (μ) RA: −1.4792 mas/yr
Dec.: −1.2312 mas/yr
Parallax (π)0.2142±0.0838 mas2
Distanceapprox. 15,000 ly
(approx. 5,000 pc)
Absolute magnitude (MV)−8.767
C
Radial velocity (Rv)−28.508 km/s
Proper motion (μ) RA: −1.5604 mas/yr
Dec.: −0.8094 mas/yr
Parallax (π)0.3679±0.0169 mas4
Distance8,900 ± 400 ly
(2,700 ± 100 pc)
Absolute magnitude (MV)−6.59
Details
A
Mass6.310–1711 M☉
Radius26310 R☉
Luminosity170,00010 L☉
Surface gravity (log g)1.07 cgs
Temperature7,3417 K
Metallicity-0.247
Rotational velocity (v sin i)2312 km/s
Age2013 Myr
C
Mass219 M☉
Radius539 R☉
Luminosity83,00014 L☉
Surface gravity (log g)2.0514 cgs
Temperature15,50014 K
Rotational velocity (v sin i)3514 km/s
Other designations
34 Cassiopeiae, HR 382, ADS 1073, CCDM J01200+5813
A: BD+57°260, GC 1594, HD 7927, HIP 6242, SAO 22191
C: NSV 466, BD+57°257, GC 1590, HD 7902, HIP 6229, SAO 22187
Database references
SIMBADdata

Phi Cassiopeiae is a multiple star system in the northern constellation of Cassiopeia. Its name is a Bayer designation that is Latinized from φ Cassiopeiae, and abbreviated Phi Cas or φ Cas. With a combined apparent magnitude of +4.95, it is visible to the naked eye. The two brightest components are A and C, sometimes called φ1 and φ2 Cas. φ Cas A is an F0 bright supergiant of magnitude 4.95 and φ Cas C is a 7.08 magnitude B6 supergiant at 134".

System

φ1 and φ2 Cassiopeiae are the two brightest stars in the field of open cluster NGC 457 (north is down). source ↗

φ Cassiopeiae appears among the stars of the open cluster NGC 457, which located at a distance of 7,800 light-years (2,400 pc), but it is uncertain whether φ Cas is a member of this cluster.13 φ Cas is generally treated as having five component stars, designated A to E in order of distance from the brightest star. The two components A and C are the brightest stars in the field of NGC 457; they are sometimes referred to as φ1 and φ2 Cassiopeiae.15 Component B is a 12th magnitude star 49" from φ1.

Components D and E and both 10th magnitude B-type main sequence stars in the field of NGC 457, with component E only 42" from φ2. Another three components are sometimes listed as components of the multiple system, although this is somewhat arbitrary with dozens of members of NGC 457 being found within a few arc-minutes.16

The two supergiants, components A and C, share a similar space motion to the other stars in NGC 457, but their evolutionary status and brightness makes them unlikely members.10 Their Gaia Data Release 2 parallaxes are comparable to other stars in the cluster and consistent with the accepted distance of NGC 457,17 and component C has been given a 70% likelihood of being a member of the cluster.18

Properties

The primary component of the φ Cassiopeiae system is a very luminous yellow supergiant. Its absolute magnitude is comparable to some yellow hypergiants but it does not show the level of mass loss and instability that would qualify it as a hypergiant itself. Various model atmospheres all give a temperature around 7,300K, a low surface gravity, a radius around 250 R☉, and a luminosity well over 100,000 L☉. More uncertain is the mass, which would be expected to have been well over 25 M☉ initially, but much less now. Different authors have published values from 6 M☉ to 17 M☉.1011

Component C is a relatively typical B class supergiant, 83,000 times the luminosity of the sun. It is a suspected variable and a suspected spectroscopic binary.19

See also

See also

References

References

  1. Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. XHIP record for this object at VizieR.
  2. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. Eggleton, P. P.; Tokovinin, A. A. (2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. S2CID 14878976.
  4. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  5. 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. Bibcode:2002yCat.2237....0D.
  6. Mermilliod, J. C.; et al. (2008). "Red giants in open clusters. XIV. Mean radial velocities for 1309 stars and 166 open clusters". Astronomy and Astrophysics. 485 (1): 303–314. Bibcode:2008A&A...485..303M. CiteSeerX 10.1.1.30.7545. doi:10.1051/0004-6361:200809664.
  7. Kovtyukh, V. V.; et al. (2012). "Accurate luminosities from the oxygen 7771-4 a triplet and the fundamental parameters of F-G supergiants". Monthly Notices of the Royal Astronomical Society. 423 (4): 3268. arXiv:1204.4115v1. Bibcode:2012MNRAS.423.3268K. doi:10.1111/j.1365-2966.2012.21117.x. S2CID 118683158.
  8. Kharchenko, N. V.; et al. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ˜55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889. arXiv:0705.0878. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776. S2CID 119323941.
  9. Leitherer, C.; Wolf, B. (1984). "Early-type stars in OB associations in the infrared. I Extinction law and IR excesses". Astronomy and Astrophysics. 132: 151. Bibcode:1984A&A...132..151L.
  10. Rosenzweig, P.; Anderson, L. (1993). "A determination of the basic atmospheric parameters of Phi Cassiopeiae". The Astrophysical Journal. 411: 207. Bibcode:1993ApJ...411..207R. doi:10.1086/172820.
  11. Arellano Ferro, A.; et al. (1988). "Comments on the variability and physical parameters of the F supergiant Phi Cassiopeiae". Astronomical Society of the Pacific. 100: 993. Bibcode:1988PASP..100..993A. doi:10.1086/132261. S2CID 122133396.
  12. Evans, Christopher J.; Howarth, Ian D. (2003). "Characteristics and classification of A-type supergiants in the Small Magellanic Cloud". Monthly Notices of the Royal Astronomical Society. 345 (4): 1223. arXiv:astro-ph/0308125. Bibcode:2003MNRAS.345.1223E. doi:10.1046/j.1365-2966.2003.07038.x. S2CID 15290757.
  13. Zhang, X. B.; et al. (2012). "B-Type Variables in the Young Open Cluster Ngc 457". The Astronomical Journal. 144 (3): 86. Bibcode:2012AJ....144...86Z. doi:10.1088/0004-6256/144/3/86. S2CID 250804951.
  14. McErlean, N. D.; et al. (1999). "Galactic B-supergiants: A non-LTE model atmosphere analysis to estimate atmospheric parameters and chemical compositions". Astronomy and Astrophysics. 349: 553. Bibcode:1999A&A...349..553M.
  15. Mark Bratton (15 September 2011). The Complete Guide to the Herschel Objects: Sir William Herschel's Star Clusters, Nebulae and Galaxies. Cambridge University Press. pp. 583–. ISBN 978-0-521-76892-4.
  16. Dommanget, J.; Nys, O. (1994). "Catalogue des composantes d'etoiles doubles et multiples (CCDM) premiere edition - Catalogue of the components of double and multiple stars (CCDM) first edition". Com. de l'Observatoire Royal de Belgique. 115: 1. Bibcode:1994CoORB.115....1D.
  17. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
  18. Cantat-Gaudin, T.; Anders, F. (2020). "Clusters and mirages: Cataloguing stellar aggregates in the Milky Way". Astronomy and Astrophysics. 633: A99. arXiv:1911.07075. Bibcode:2020A&A...633A..99C. doi:10.1051/0004-6361/201936691. S2CID 208138247.
  19. Mayer, Pavel; et al. (1998). "Radial velocities of six early-type evolved stars". Astrophysics and Space Science. 262 (2): 163. Bibcode:1994CoSka..24...65M. doi:10.1023/A:1001840718226. S2CID 118901569.