AO Cassiopeiae

AO Cassiopeiae

AO Cassiopeiae (HD 1337A and B) is one of the most massive and luminous binary systems known. It is an elliptic and semidetached eclipsing binary consisting of two O stars (O9III) of 32 solar masses and 23 solar radii, and 30 solar masses and 15 solar radii, respectively. The two stars orbit so closely, with a period of only 3.52 days, that their surfaces are almost touching and highly distorted, and there is a continuous exchange of matter. The typical separation between the stars is somewhere between 2.5 and 3 times the primary stellar radius.


AO Cas, also known as Pearce's Star, lies about 7,000 light-years away in the constellation Cassiopeia.