15 Canis Majoris

One of an apparent trio of relatively faint stars in central Canis Major, southward and eastward from bright Sirius. 15 Canis Majoris is a hot blue star with a surface temperature some five times that of the Sun, and seven times the Sun's diameter. It is highly luminous star, emitting approximately 1,400 times more visible light than the Sun (and nearly 20,000 times as much energy in all wavelengths). There is some question over its full spectral classification; some sources describe it as a type Ib supergiant (and its absolute magnitude of -3.05 supports this classification), but others prefer to list it as a type IV subgiant star.

15 Canis Majoris lies some 1,200 light years from the Sun, and shines with a slightly variable magnitude. It is a pulsating variable of the Beta Cephei type, meaning that the star contracts and expands over a regular period of a littler more than four hours. As it contracts, it is also increases in brightness so that, as seen from Earth, the star's magnitude varies between +4.82 and +4.80 (an approximately 2% increase in its apparent brightness). As a variable star, 15 Canis Majoris is also catalogued with the variable designation of 'EY Canis Majoris'.