Marfak

At fourth magnitude, this star in the northern constellation of Cassiopeia is relatively faint, but nonetheless usually visible to the naked eye. It lies southward of the famous 'W' shape that makes up the body of Cassiopeia, forming a close visual pair with Mu Cassiopeiae, which is less than half a degree away in the sky. Indeed, the name Marfak (from the Arabic for 'elbow') is sometimes also used for the neighbouring Mu star. The same etymology of 'elbow' also lies behind the name Mirfak given to Alpha Persei, and also to Marfik for Lambda Ophiuchi (these various stars represent the elbows of their respective constellations, and have no other relation to one another).

Marfak is a white main-sequence star that lies some 137 light years from the Sun, based on the most recent parallax data. It is rather larger, hotter and more luminous than the Sun, having a diameter some 2.6 times greater, and shining nearly thirty times more brightly. The star has no known companions, but does show indications of posessesing a circumstellar disc. The question of its variability, if any, is unsettled, though there are signs that it may belong to the pulsating Delta Scuti class of variables. The motion of Marfak through space implies that it may have some historical relation with the stars of the Hyades cluster in Taurus.