S Persei

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S Persei
Double Cluster.jpg
GoldF39400 circle.svg

Location of S Persei (circled) near the Double Cluster (north is left)
Observation data
Epoch J2000      Equinox J2000
Constellation Perseus
Right ascension 2h 22m 51.70928s[1]
Declination 58° 31′ 11.4476″[1]
Apparent magnitude (V) 9.23[2] (7.9 - 12.0[3])
Spectral type M4.5I[2] (M3Iae - M7[3])
B−V color index 2.65[2]
Variable type SRc[3]
Radial velocity (Rv) -39.71[4] km/s
Proper motion (μ) RA: −0.49 ± 0.23[5] mas/yr
Dec.: −1.19 ± 0.20[5] mas/yr
Parallax (π) 0.413 ± 0.017[5] mas
Distance 7,900 ± 300 ly
(2,420 ± 100 pc)
Absolute magnitude (MV) −6.36 (at mV 9.23)[2]
Mass 20[6] M
Radius 780 - 1,230[2] R
Luminosity 86,000 - 186,000[7][8][9] L
Surface gravity (log g) 0.0[10] cgs
Temperature 3,000[11]–3,600[7] K
Other designations
S Per, HD 14528, HIP 11093, BD+57°552, SAO 23261, WDS J02229+5835, AAVSO 0215+58
Database references

S Persei is a red supergiant located near the Double Cluster in Perseus, north of the cluster NGC 869. It is a member of the Perseus OB1 association and one of the largest known stars. It is also a semiregular variable, a star whose variations are less regular than those of Mira variables.


S Persei was named by German astronomer Adalbert Krueger in 1874 after observing that it varied in brightness.[12] It was subsequently listed in major stellar catalogues of that era as HD 14528 and BD+57 552.


S Persei varies slowly by several magnitudes, a factor of over 40 in brightness. It has a main period of somewhat over two years, but shows significant unpredictability. There is a strong variation in the amplitude from around one magnitude to about four magnitudes, and these have been interpreted as beats due to a second period of about 940 days.[13] Other analyses find only the primary period of 813 ± 60 days.[14]

S Persei is classified as a semiregular variable star of type SRc, indicating that it is a supergiant, and it has one of the largest visual amplitudes of any variable of this type.[3] While the General Catalogue of Variable Stars lists it as varying between magnitudes 7.9 and 12.0, it has since been seen fainter.[14]

The spectral type of S Persei also varies. Typically it is a red supergiant of spectral class M3 or M4, but particularly at deep visual minima it may show a much cooler spectral type of M7 or M8, highly unusual for a supergiant.[15]


Many of the visually bright variable stars belong to this class of semiregulars, as these stars are extremely large and luminous, and hence visible across long distances. S Persei could be as small with a radius 780 times the sun's radius (R), but could be larger with a radius 1,230 times that of the sun.[2] It has been described as a hypergiant.[16] Its angular diameter has been measured directly and found to be somewhat elliptical. Modelled as a uniform disk, the radius corresponds to 1,212±124 R.[17]

The temperature has been calculated from the spectrum using a DUSTY model,[18] giving an effective photospheric temperature of 3,600 K and a temperature of 900 K for the surrounding dust torus.[7] This is consistent with previous studies, but the derived luminosity from different authors varies from 86,000 L to 186,000 L.[7][8] Older studies frequently calculated higher luminosities and lower temperatures.[19]

The mass of S Persei is also uncertain, but expected to be around 20 M.[6] Mass is being lost at 6.8×10−6 M per year,[8] leading to an extensive and complex circumstellar environment of gas and dust.[7]


S Persei is surrounded by clouds containing water molecules which produce maser emission. This allows the distance to be measured very accurately using very long baseline interferometry, giving an annual parallax of 0.413 ± 0.017 milliarcseconds. For comparison the Hipparcos parallax is 1.88 mas, but the margin of error is larger than the parallax value itself.[1] It lies somewhat further away than the centres of the Double Cluster open clusters, but definitely within the Per OB1 association and the Perseus Arm of the galaxy.[5]

S Persei is a double star. The red supergiant has an A0 11th magnitude companion at 69".[20] There are also several other 8th to 10th magnitude stars within half a degree of S Persei.[21]


  1. ^ a b c 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 d e f Emily M. Levesque; Philip Massey; K. A. G. Olsen; Bertrand Plez; et al. (August 2005). "The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not As Cool As We Thought". The Astrophysical Journal. 628 (2): 973–985. arXiv:astro-ph/0504337Freely accessible. Bibcode:2005ApJ...628..973L. doi:10.1086/430901. 
  3. ^ a b c d Samus', N. N.; Goranskii, V. P.; Durlevich, O. V.; Zharova, A. V.; Kazarovets, E. V.; Kireeva, N. N.; Pastukhova, E. N.; Williams, D. B.; Hazen, M. L. (2003). "An Electronic Version of the Second Volume of the General Catalogue of Variable Stars with Improved Coordinates". Astronomy Letters. 29 (7): 468. Bibcode:2003AstL...29..468S. doi:10.1134/1.1589864. 
  4. ^ 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". Astronomy and Astrophysics. 430 (1): 165–186. arXiv:astro-ph/0409579Freely accessible. Bibcode:2005A&A...430..165F. doi:10.1051/0004-6361:20041272. ISSN 0004-6361. 
  5. ^ a b c d Asaki, Y.; Deguchi, S.; Imai, H.; Hachisuka, K.; Miyoshi, M.; Honma, M. (2010). "DISTANCE AND PROPER MOTION MEASUREMENT OF THE RED SUPERGIANT, S PERSEI, WITH VLBI H2O MASER ASTROMETRY". The Astrophysical Journal. 721 (1): 267–277. arXiv:1007.4874Freely accessible. Bibcode:2010ApJ...721..267A. doi:10.1088/0004-637X/721/1/267. ISSN 0004-637X. 
  6. ^ a b Yates, J. A.; Cohen, R. J. (1994). "Circumstellar Envelope Structure of Late Type Stars as Revealed by MERLIN Observations of 22-GHZ Water Masers". Monthly Notices of the Royal Astronomical Society. 270 (4): 958. Bibcode:1994MNRAS.270..958Y. doi:10.1093/mnras/270.4.958. 
  7. ^ a b c d e Fok, Thomas K. T.; Nakashima, Jun-Ichi; Yung, Bosco H. K.; Hsia, Chih-Hao; Deguchi, Shuji (2012). "Maser Observations of Westerlund 1 and Comprehensive Considerations on Maser Properties of Red Supergiants Associated with Massive Clusters". The Astrophysical Journal. 760: 65. arXiv:1209.6427Freely accessible. Bibcode:2012ApJ...760...65F. doi:10.1088/0004-637X/760/1/65. 
  8. ^ a b c Mauron, N.; Josselin, E. (2011). "The mass-loss rates of red supergiants and the de Jager prescription". Astronomy and Astrophysics. 526: A156. arXiv:1010.5369Freely accessible. Bibcode:2011A&A...526A.156M. doi:10.1051/0004-6361/201013993. 
  9. ^ Verhoelst, T.; Van Der Zypen, N.; Hony, S.; Decin, L.; Cami, J.; Eriksson, K. (2009). "The dust condensation sequence in red supergiant stars". Astronomy and Astrophysics. 498: 127. arXiv:0901.1262Freely accessible. Bibcode:2009A&A...498..127V. doi:10.1051/0004-6361/20079063. 
  10. ^ Gonzalez, Guillermo; Wallerstein, George (2000). "Elemental Abundances in Evolved Supergiants. II. The Young Clusters H and χ Persei". The Astronomical Journal. 119 (4): 1839. Bibcode:2000AJ....119.1839G. doi:10.1086/301319. 
  11. ^ 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. 
  12. ^ Krüger, A. (1874). "Anzeige eines neuen veränderlichen Sternes (S Persei)". Astronomische Nachrichten. 83 (10): 157. Bibcode:1874AN.....83..157K. doi:10.1002/asna.18740831005. 
  13. ^ Smith, Horace A. (1974). "S Persei a Semi-Regular Variable with Two Periods". Journal of the American Association of Variable Star Observers. 3: 20. Bibcode:1974JAVSO...3...20S. 
  14. ^ a b Kiss, L. L.; Szabó, Gy. 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. 
  15. ^ Wing, R. F. (2009). "The Biggest Stars of All". The Biggest. 412: 113. Bibcode:2009ASPC..412..113W. 
  16. ^ Zhang, B.; Reid, M. J.; Menten, K. M.; Zheng, X. W.; Brunthaler, A. (2012). "The distance and size of the red hypergiant NML Cygni from VLBA and VLA astrometry". Astronomy & Astrophysics. 544: A42. arXiv:1207.1850Freely accessible. Bibcode:2012A&A...544A..42Z. doi:10.1051/0004-6361/201219587. ISSN 0004-6361. 
  17. ^ Thompson, R. R.; Creech-Eakman, M. J. (2003). "Interferometric observations of the supergiant S Persei: Evidence for axial symmetry and the warm molecular layer". American Astronomical Society Meeting 203. 203: 49.07. Bibcode:2003AAS...203.4907T. 
  18. ^ Ivezic, Zeljko; Nenkova, Maia; Elitzur, Moshe (1999). "User Manual for DUSTY". arXiv:astro-ph/9910475Freely accessible. 
  19. ^ De Jager, C.; Nieuwenhuijzen, H.; Van Der Hucht, K. A. (1988). "Mass loss rates in the Hertzsprung-Russell diagram". Astronomy and Astrophysics Supplement Series (ISSN 0365-0138). 72: 259. Bibcode:1988A&AS...72..259D. 
  20. ^ 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'Observ. Royal de Belgique. 115: 1. Bibcode:1994CoORB.115....1D. 
  21. ^ Skiff, B. A. (1994). "Photometry of Stars in the Field of S Persei". Information Bulletin on Variable Stars. 4054: 1. Bibcode:1994IBVS.4054....1S.