Iota Canis Majoris

A fourth magnitude star in Canis Major, lying less than three degrees to the east of Sirius, the brightest star in the sky. Iota Canis Majoris is a brilliant star in its own right, generating about 10,000 times as much light as the Sun (and more than 100,000 times as much radiation across the full spectrum). It has an absolute magnitude of -5.1, which means that, if Iota Canis Majoris were ten parsecs from the Sun, it would shine more brightly than Venus in the skies of Earth. At its actual distance of more than 2,500 light years, it is much fainter, but nonetheless still visible to the naked eye.

Iota Canis Majoris a hot blue star of the type classified as a supergiant, and is thought to be a pulsating variable of the Beta Cephei type. Its variability is caused by a layer of iron within the star, and physical processes working on this iron layer cause the entire star to swell and contract over time. For an observer on Earth, this causes the star's apparent magnitude to fluctuate slightly, from +4.36 at its brightest down to +4.40 at its faintest.