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NGC 7635 annotated.jpg
NGC 7635 surrounding BD+60 2522
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
Observation data
Epoch J2000      Equinox J2000
Constellation Cassiopeia
Right ascension  23h 20m 44.5203s[1]
Declination +61° 11′ 40.561″[1]
Apparent magnitude (V) 8.67[2]
Spectral type O6.5(f)(n)p[3]
U−B color index −0.62[2]
B−V color index +0.41[2]
Radial velocity (Rv)−26[4] km/s
Proper motion (μ) RA: 3.10[1] mas/yr
Dec.: 4.60[1] mas/yr
Parallax (π)13.0 ± 8.0[5] mas
Distance2,400[6] pc
Absolute magnitude (MV)−5.5[6]
Mass44 M
Radius15 R
Luminosity398,000 L
Temperature37,500 K
Rotational velocity (v sin i)178 - 240 km/s
Age2[8] Myr
Other designations
SAO 20575 IRAS 23185+6055 2MASS J23204452+6111404
Database references

BD+60°2522 is a bright O-Type star that has produced the Bubble Nebula (NGC 7635) with its stellar wind. The exact classification of the star is uncertain, with a number of spectral peculiarities and inconsistencies between the appearance of the star itself and the effects on the nearby nebulosity, but it is undoubtedly a highly luminous hot massive star.[6] Direct spectroscopy yields a spectral class of O6.5 and an effective temperature around 37,500K. It is a member of the Cassiopeia OB2 stellar association in the Perseus Arm[8] of the galaxy at about 8,500 light-years' distance.[9]

Although BD+60°2522 is around two million years old, the surrounding nebula is apparently only about 40,000 years old. The bubble is expected to be formed as a shock front where the stellar wind meets interstellar material at supersonic speeds. The wind from BD+60°2522 is travelling outwards at 1,800–2,500 km/s, causing the star to lose over a millionth of the mass of the Sun every year.[8]


  1. ^ a b c d Hog, E.; Kuzmin, A.; Bastian, U.; Fabricius, C.; Kuimov, K.; Lindegren, L.; Makarov, V. V.; Roeser, S. (1998). "The TYCHO Reference Catalogue". Astronomy and Astrophysics. 335: L65. Bibcode:1998A&A...335L..65H.
  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. ^ Walborn, Nolan R.; Howarth, Ian D.; Evans, Christopher J.; Crowther, Paul A.; Moffat, Anthony F. J.; St-Louis, Nicole; Fariña, Cecilia; Bosch, Guillermo L.; Morrell, Nidia I.; Barbá, Rodolfo H.; Van Loon, Jacco Th. (2010). "The Onfp Class in the Magellanic Clouds". The Astronomical Journal. 139 (3): 1283. arXiv:1001.4032. Bibcode:2010AJ....139.1283W. doi:10.1088/0004-6256/139/3/1283.
  4. ^ Wilson, Ralph Elmer (1953). General Catalogue of Stellar Radial Velocities. Carnegie Institution of Washington. Bibcode:1953GCRV..C......0W. LCCN 54001336.
  5. ^ Jenkins, Louise F. (1952). General Catalogue of Trigonometric Stellar Parallaxes. Yale University Observatory. LCCN 53001043.
  6. ^ a b c Moore, B. D.; Walter, D. K.; Hester, J. J.; Scowen, P. A.; Dufour, R. J.; Buckalew, B. A. (2002). "Hubble Space Telescope Observations of the Windblown Nebula NGC 7635". The Astronomical Journal. 124 (6): 3313. Bibcode:2002AJ....124.3313M. doi:10.1086/344596.
  7. ^ Rauw, G.; De Becker, M.; Vreux, J. -M. (2003). "Line profile variability in the spectra of Oef stars". Astronomy and Astrophysics. 399: 287. arXiv:astro-ph/0408253. Bibcode:2003A&A...399..287R. doi:10.1051/0004-6361:20021776.
  8. ^ a b c Anand, M. Y.; Kagali, B. A.; Murthy, Jayant (2009). "Study of Bubble nebula using IUE high resolution spectra". Bulletin of the Astronomical Society of India. 37: 1. arXiv:0903.2828. Bibcode:2009BASI...37....1A.
  9. ^ Mason, Brian D.; Hartkopf, William I.; Gies, Douglas R.; Henry, Todd J.; Helsel, John W. (2009). "The High Angular Resolution Multiplicity of Massive Stars". The Astronomical Journal. 137 (2): 3358. arXiv:0811.0492. Bibcode:2009AJ....137.3358M. doi:10.1088/0004-6256/137/2/3358.