Cor Caroli

The brightest star in Canes Venatici has a name that comes from the Latin for the 'Heart of Charles'. It was evidently named for one of the two English Kings named Charles, though opinion is divided on which of these two kings it was intended to honour (the weight of evidence is in favour of Charles I, executed after the English Civil War, but some legends associate the star with the return of his son Charles II to take up the restored monarchy).

Cor Caroli's constellation of Canes Venatici lies southward of the Plough in Ursa Major, and the star can be easily located through that famous asterism. Following an imaginary line southeastwards from Dubhe through Phecda in the bowl of the Plough leads the eye along a path that passes close by Cor Caroli. The star belongs to the large spring asterism of the Great Diamond, forming the Diamond's upper tip and creating a near-equilateral triangle with Arcturus in Boötes and Denebola at the tail of Leo.

Cor Caroli is a binary system some 107 light years from the Solar System, with its two component stars widely separated from one another. The brighter of the two is designated Alpha² Canum Venaticorum, a white star whose unusually metal-rich nature gives it a remarkably intense magnetic field. That field in turn causes dense starspots to mottle its surface, leading to characteristic shifts in its brightness over time. This component of the Cor Caroli system is the prototype of variable stars showing similar properties, which are collectively known as Alpha² Canum Venaticorum variables. The fainter of the two components, Alpha¹, is an F-type dwarf star