· · · ·


Theta Cassiopeiae, 33 Cassiopeiae

Proper NameMarfak
Bayer DesignationTheta Cassiopeiae
Flamsteed Number33 Cassiopeiae
HR (BSC)343
Right Ascension1h 11m 6s
Declination+55° 9' 0"
Distance137 light years
42 parsecs
MagnitudeApparent: +4.34
Absolute: +1.23
Spectral ClassA7V white main sequence star
Optimum VisibilityOctober (Usually visible from northern latitudes)

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).

The fainter yellow star to the southwest of Marfak is Mu Cassiopeiae. As seen from Earth. the two stars are separated by just twenty-eight arcminutes, and the name Marfak is ocassionally applied to yellow Mu Cassiopeiae as well as white Theta Cassiopeiae. In fact, the two stars are widely separated in space. Yellow Mu Cassiopeiae is a much less luminous dwarf (or possibly subdwarf) star, but one that lies far closer to the Sun than its brighter neighbour in the sky. Imagery provided by Aladin sky atlas

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.


Related Entries