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] (M3-M6Ia[4])
B−V color index 2.65[2]
Variable type SRc[3]
Radial velocity (Rv) -39.71[5] km/s
Proper motion (μ) RA: -2.70[1] mas/yr
Dec.: -0.29[1] mas/yr
Parallax (π) 1.66 ± 1.81[1] mas
Distance 7,890 ly
(2,420[6] pc)
Absolute magnitude (MV) -6.36[2]
Radius 780-1,230[2] R
Luminosity 88,000 - 221,000[2] L
Temperature ~3,500[2] 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 is a semiregular variable, stars whose periods of variation are subject to more irregularities than those of Mira variables.

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 may be over 1,000 times the sun's radius (R), but the most likely value is 780 R.[2] It has been described as a hypergiant.[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 a spectroscopic parallax of 0.413 ± 0.017 arc seconds. For comparison the Hipparcos parallax is 1.88", but the margin of error is larger than the parallax value itself. 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.[6]

S Persei is a double star. The red supergiant has an A0 11th magnitude companion at 69".[8] There are also several other 8th to 10th magnitude stars within half a degree of S Persei.[9]

See also[edit]


  1. ^ a b c d e Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653. arXiv:0708.1752free to read. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d e f g h 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/0504337free to read. Bibcode:2005ApJ...628..973L. doi:10.1086/430901. 
  3. ^ a b 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. ^ Richards, A. M. S.; Yates, J. A.; Cohen, R. J. (1999). "Maser mapping of small-scale structure in the circumstellar envelope of S Persei". Monthly Notices of the Royal Astronomical Society. 306 (4): 954–974. Bibcode:1999MNRAS.306..954R. doi:10.1046/j.1365-8711.1999.02606.x. ISSN 0035-8711. 
  5. ^ 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/0409579free to read. Bibcode:2005A&A...430..165F. doi:10.1051/0004-6361:20041272. ISSN 0004-6361. 
  6. ^ a b 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:1007.4874free to read. Bibcode:2010ApJ...721..267A. doi:10.1088/0004-637X/721/1/267. ISSN 0004-637X. 
  7. ^ 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:1207.1850free to read. Bibcode:2012A&A...544A..42Z. doi:10.1051/0004-6361/201219587. ISSN 0004-6361. 
  8. ^ 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. 
  9. ^ Skiff, B. A. (1994). "Photometry of Stars in the Field of S Persei". Information Bulletin on Variable Stars. 4054: 1. Bibcode:1994IBVS.4054....1S.