Cor Caroli system

Cor Caroli (α CVn, α Canum Venaticorum, Alpha Canum Venaticorum) is a binary star consisting of two distantly separated components. The brighter of the two stars is designated α² Canum Venaticorum, the fainter α¹ Canum Venaticorum.

α² Canum Venaticorum has spectral type A0. It is a chemically peculiar star with a strong magnetic field, and is also classified as an Ap/Bp star. Its atmosphere has overabundances of some elements, such as silicon, mercury, and europium. This is thought to be due to some elements sinking down into the star under the force of gravity while others are elevated by radiation pressure. This star is the prototype of a class of variable stars, the so-called α² Canum Venaticorum stars. The strong magnetic field of these stars is believed to produce starspots of enormous extent. Due to these starspots the brightness of α² Canum Venaticorum stars varies considerably during their rotation.