Cassiopeia

This page was last amended on 30th November, 2007

The distinctive bright, "W"-shaped asterism represents the chair upon which the queen Cassiopeia sits. It is surrounded by the Milky Way.

Navi (gamma Cassiopeiae), of magnitude 2.15, has a faint companion, very difficult to spot because of the brightness of Navi itself.

Eta Cassiopeiae, magnitude 3.46, is a binary, each star a different colour, yellow and red. The companion orbits the primary every 480 years.

There are many other multiples, including Lambda, Iota, Omicron and Phi.

There are also a number of variable stars in Cassiopeia, including the second and third brightest.

Caph (beta Cassiopeiae) has a period of 2h 30m 11s. Its magnitude range is 2.25-2.31.

Gamma Cassiopeiae is a prototype of an important class of variable consisting of very rapidly rotating subgiants or dwarfs. The magnitude variation is usually small. Strangely, gamma Cassiopeiae itself, which has a magnitude range of 1.5 to 3.0 with a period of approximately 17 hours, is not typical of the class.

Cassiopeia has two Messier objects.

M52 (magnitude 6.9) is an open cluster of about 120 stars. A 60mm or larger telescope is required to see it. It can be found by using Schedar and Caph as pointers, continuing an imaginary line a little greater than the distance between the two stars. It can just be seen in our star chart.

M103 (magnituede 7.4) is also an open cluster, with about forty stars. Its position can be deduced from the star chart above. It is best seen using binoculars.

There are other deep-sky objects in Cassiopeia, but really appeal only to those with a special interest in the subject.