Epsilon Carinae

Epsilon Carinae (ε Car, ε Carinae) is a star in the southern constellation of Carina. It is also known by the name Avior. At apparent magnitude +1.86 it is one of the brightest stars in the night sky, but is not visible from the northern hemisphere.

Epsilon Carinae is a double star located roughly 560–660 light-years (170–200 parsecs) away from the Earth. Measurements during the Hipparcos mission give the pair an angular separation of 0.46 arcseconds with a difference in magnitude of 2.0. At their estimated distance, this angle is equivalent to a physical separation of around 4 Astronomical Units. This pair may form an eclipsing binary system with a period of 785 days (2.15 years), resulting in a magnitude change of 0.12 during each eclipse.

The primary component has an apparent visual magnitude of 2.2, which by itself would still make it the third brightest star in the constellation. It is an evolved giant star with a stellar classification of K0 III. However, examination of the ultraviolet flux from this star suggests it may instead be of spectral type K7. The fainter secondary companion has an apparent visual magnitude of 4.1, which, if it were a solitary star, would be bright enough to be seen with the naked eye. This is a hot, core hydrogen-fusing B-type main sequence star of spectral class B2 Vp. The secondary may itself have an orbiting stellar companion of spectral class F8:.