PZ Cassiopeiae

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PZ Cassiopeiae
Cassiopeia constellation map.svg
Location of PZ Cas
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
Distance 2,810+220
[7] pc
Absolute magnitude (MV) −7.89[4]
Radius 1,190 (-1,940)[4] R
Luminosity 240,000–270,000[7] L
Surface gravity (log g) −0.5[4] cgs
Temperature 3,600[4] K
Age 8 – 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 estimates at 1,190–1,940 times the Sun's radius. Its distance from Earth was initially estimated to be around 7800 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, a radius 1,260–1,340 the solar one, and an initial mass 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[edit]

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]


  1. ^ a b c d Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653. arXiv:0708.1752Freely accessible. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. 
  2. ^ a b c 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. ^ a b c 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/0608438Freely accessible. Bibcode:2006MNRAS.372.1721K. doi:10.1111/j.1365-2966.2006.10973.x. 
  4. ^ a b c d e 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/0504337Freely accessible. Bibcode:2005ApJ...628..973L. doi:10.1086/430901. 
  5. ^ a b 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/0409579Freely accessible. Bibcode:2005A&A...430..165F. doi:10.1051/0004-6361:20041272. 
  7. ^ a b c d e 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:1308.3580Freely accessible. Bibcode:2013ApJ...774..107K. doi:10.1088/0004-637X/774/2/107. 
  8. ^ Samus, N. N.; Durlevich, O. V.; et al. (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/0609106Freely accessible. 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. 
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