Kappa Piscium

The southernmost of the ring of seven faint stars that form the Circlet, the body of the western fish of Pisces. Kappa Piscium and its Circlet formation stand directly to the south of the prominent Square of Pegasus in the sky. It is a white star, about twice the diameter of the Sun, that lies some 161 light years from the Solar System.

Kappa Piscium is notable as being a variable star, belonging to the class known as Alpha² Canum Venaticorum variables. Variations in the star's intense magnetic field cause heavy metals (particularly strontium) to distribute itself unevenly on the star's surface layers, causing its luminosity to apparently vary as it rotates on its axis. This patterning means that it is possible to measure how quickly Kappa Piscium rotates: it takes some forty-eight hours to complete one rotation (that is, the star rotates nearly thirteen times faster than the Sun).

Kappa Piscium is one of the brighter members of a loosely connected group of about a hundred stars known collectively as the AB Doradus Moving Group. Thought to share a common origin about four hundred million years ago, these stars are now widely spread across the sky. Most are extremely faint as seen from Earth, but other prominent members of the same group include Rukbat in Sagittarius and Alnair in Grus.