AO Cassiopeiae

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AO Cas A/B
Observation data
Epoch J2000      Equinox J2000
Constellation Cassiopeia
Right ascension 00h 17m 43.0617s
Declination +51° 25′ 59.125″
Apparent magnitude (V) 6.102
Spectral type O9III + O9III
Variable type β Lyr
Radial velocity (Rv) -35.2 km/s
Proper motion (μ) RA: -4.19 mas/yr
Dec.: -1.62 mas/yr
Parallax (π) 0.57 ± 0.69 mas
Distance approx. 6,000 ly
(approx. 2,000 pc)
AO Cas A
Mass 20.30-57.75[1] M
Radius 11.5 / 7.5 R
AO Cas B
Mass 14.8-31.73[1] 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.[1] 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.[2] Stars of this brightness are generally just visible to the unaided eye in dark skies in semirural locations.[3]

The component stars are so close to each other they are ellipsoidal (egg-shaped).[4]


  1. ^ 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 
  2. ^ Watson, Christopher (4 January 2010). "AO Cassiopeiae". AAVSO Website. American Association of Variable Star Observers. Retrieved 15 February 2014. 
  3. ^ Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. Sky Publishing Corporation. Retrieved 5 February 2014. 
  4. ^ [1]

External links[edit]