AO Cassiopeiae

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AO Cas A/B
Observation data
Epoch J2000      Equinox J2000
Constellation Cassiopeia
Right ascension 00h 17m 43.062s[1]
Declination +51° 25′ 59.12″[1]
Apparent magnitude (V) 6.102
Spectral type O9III + O9III
Variable type β Lyr
Radial velocity (Rv) −35.2 km/s
Proper motion (μ) RA: −3.98 ± 0.35[1] mas/yr
Dec.: −1.76 ± 0.29[1] mas/yr
Parallax (π) 1.36 ± 0.44[1] mas
Distance approx. 2,400 ly
(approx. 700 pc)
AO Cas A
Mass 20.30-57.75[2] M
Radius 11.5 / 7.5 R
AO Cas B
Mass 14.8-31.73[2] M
Other designations
AO Cas, Pearce's Star, HR 65, BD+50 46A, HD 1337, SAO 21273, HIP 1415.
Database references

AO Cassiopeiae, also known as Pearce's Star, is a binary system, composed of two massive hot blue stars of spectral types O7/O9III and O8/O9III that each weigh anywhere between 20.30 and 57.75 times and 14.8 and 31.73 times the mass of our Sun respectively.[2] The system is an eclipsing binary with a period of roughly 3.5 days, with the apparent magnitude ranging between 6.07 and 6.24.[3] Stars of this brightness are generally just visible to the unaided eye in dark skies in semirural locations.[4]

The component stars are so close to each other they are ellipsoidal (egg-shaped).[5]


  1. ^ a b c d e van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. Vizier catalog entry
  2. ^ a b c Hohle, M. M.; Neuhäuser, R.; Schutz, B. F. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten 331 (4): 349, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355 
  3. ^ Watson, Christopher (4 January 2010). "AO Cassiopeiae". AAVSO Website. American Association of Variable Star Observers. Retrieved 15 February 2014. 
  4. ^ Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. Sky Publishing Corporation. Retrieved 5 February 2014. 
  5. ^ [1]

External links[edit]