PZ Cassiopeiae

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PZ Cassiopeiae
LBN 114.55+00.22.jpg
PZ Cassiopeiae is the bright star towards upper right in this WISE infrared image.
Observation data
Epoch J2000      Equinox J2000
Constellation Cassiopeia
Right ascension 23h 44m 03.28104s[1]
Declination +61° 47′ 22.1823″[1]
Apparent magnitude (V) 8.90[2] (8.2 - 10.2[3])
Spectral type M3I[4]
U−B color index +1.32[2]
B−V color index +2.58[2]
Variable type SRc[5]
Radial velocity (Rv)-45.68 ± 0.68[6] km/s
Proper motion (μ) RA: −4.15[1] mas/yr
Dec.: −3.55[1] mas/yr
Parallax (π)0.356 ± 0.026[7] mas
[7] pc
Absolute magnitude (MV)−7.89[4]
Radius1,190 (or 1,940)[4] R
Diameter1,190 (or 1,940)[4] D
Luminosity240,000–270,000[7] L
Surface gravity (log g)−0.5[4] cgs
Temperature3,600[4][7] K
Age8 – 10[7] Myr
Other designations
PZ Cas, IRC +60417, HIP 117078, BD+60°2613, RAFGL 3138
Database references

PZ Cassiopeiae is a red supergiant star located in the Cassiopeia constellation, and a semi-regular variable star.


PZ Cas is an extreme luminous red supergiant star, one of the largest stars currently known with an estimate of 1,190 times the Sun's radius (D), and also one of most luminous of its type with 213,000 times more luminous than the Sun (L). A radius of 1,940 D and a bolometric luminosity of 570,000 L derived by a different method is considered to be dubious. Its distance from Earth was initially estimated to be around 7,800 light-years (2.4 kiloparsecs). Subsequent studies of the star using the water masers that surround it have allowed to refine both the distance and the parameters of this star, deriving a distance of 9,160 light-years (2.81 kiloparsecs) that translates into a luminosity for it of between 240,000 and 270,000 times the Sun's luminosity, and an initial mass of 20 to 25 times that of the Sun. These parameters are all similar to those estimated for the red hypergiant VY Canis Majoris. It is likely to be part of the Cas OB5 stellar association although apparently much younger than the other stars in the association.[7]

PZ Cas is a slow semi-regular variable star with the period quoted as 925 days in the General Catalogue of Variable Stars,[8] although periods of 850 and 3,195 days have been derived.[5][3] The visual range is approximate magnitude 8-10, large for this type of variable.[3]

Supergiant or AGB star

PZ Cas has traditionally been treated as a massive supergiant, comparable to others such as VY CMa, but there is some evidence that it is a less massive Asymptotic Giant Branch (AGB) or post-AGB star. It shows enrichment of Zr and Ba, but not Li as would be expected for a true supergiant.[9]


PZ Cas has a companion, a 13th magnitude star 12" away.[10]

See also


  1. 1.0 1.1 1.2 1.3 Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653. arXiv:0708.1752. Bibcode 2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. 2.0 2.1 2.2 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. Bibcode 2002yCat.2237....0D.
  3. 3.0 3.1 3.2 Kiss, L. L.; Szabó, G. M.; Bedding, T. R. (2006). "Variability in red supergiant stars: Pulsations, long secondary periods and convection noise". Monthly Notices of the Royal Astronomical Society 372 (4): 1721. arXiv:astro-ph/0608438. Bibcode 2006MNRAS.372.1721K. doi:10.1111/j.1365-2966.2006.10973.x.
  4. 4.0 4.1 4.2 4.3 4.4 Levesque, E. M.; Massey, P.; Olsen, K. A. G.; Plez, B.; Josselin, E.; Maeder, A.; Meynet, G. (2005). "The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not as Cool as We Thought". The Astrophysical Journal 628 (2): 973. arXiv:astro-ph/0504337. Bibcode 2005ApJ...628..973L. doi:10.1086/430901.
  5. 5.0 5.1 Le Squeren, A. M.; Sivagnanam, P.; Dennefeld, M.; David, P. (1992). "A Complete Survey of OH / Infrared Objects from the IRAS LRS Sources Within a Domain of the Color Diagram". Astronomy and Astrophysics 254: 133. Bibcode 1992A&A...254..133L.
  6. Famaey, B.; Jorissen, A.; Luri, X.; Mayor, M.; Udry, S.; Dejonghe, H.; Turon, C. (2005). "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters". Astronomy and Astrophysics 430: 165. arXiv:astro-ph/0409579. Bibcode 2005A&A...430..165F. doi:10.1051/0004-6361:20041272.
  7. 7.0 7.1 7.2 7.3 7.4 7.5 Kusuno, K.; Asaki, Y.; Imai, H.; Oyama, T. (2013). "Distance and Proper Motion Measurement of the Red Supergiant, Pz Cas, in Very Long Baseline Interferometry H2O Maser Astrometry". The Astrophysical Journal 774 (2): 107. arXiv:1308.3580. Bibcode 2013ApJ...774..107K. doi:10.1088/0004-637X/774/2/107.
  8. Samus, N. N.Expression error: Unrecognized word "etal". (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally published in: 2009yCat....102025S 1. Bibcode 2009yCat....102025S.
  9. García-Hernández, D. A.; García-Lario, P.; Plez, B.; Manchado, A.; d'Antona, F.; Lub, J.; Habing, H. (2007). "Lithium and zirconium abundances in massive Galactic O-rich AGB stars". Astronomy and Astrophysics 462 (2): 711. arXiv:astro-ph/0609106. Bibcode 2007A&A...462..711G. doi:10.1051/0004-6361:20065785.
  10. Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal 122 (6): 3466. Bibcode 2001AJ....122.3466M. doi:10.1086/323920.