Cassiopeia - stuff for Em's entry
Created | Updated Jun 13, 2003
Hi Em, please don't take any of this until I let you know it's ready- these are just some notes until I get something sorted. By all means leave me a note and comment (same goes for anyone else knowledgable on the subject).
General
Cassiopeia is a conspicuous W - shaped constellation located near the north celestial pole, roughly opposite the Big Dipper in relation to the celestial pole1. The constellation covers an angular area of about 598 square degrees, ranking 9th largest of the internationally recognised constellations.
Cassiopeia is associated with the Perseus constellation family, which extends approximately parallel to the Milky Way and includes Cepheus, the royal consort of Cassiopeia lying to the north and west of the Lady; Andromeda; the body of Perseus; Pegasus; the Whale Cetus2; and the Charioteer Auriga.
In Arabian countries, Cassiopeia is called Caph3.
stars and other objects
Basics
- Irregularly variable stars
- Alpha Cas
- Gamma Cas
- Double star
- Eta Cas
- Triple star
- Iota Cas
- Variable Star
- Rho Cas
- Diffuse Nebulae
- I 1805
- I1848
- I 59
- NGC 281
- Planetary Nebula
- NGC 7635
- Open star clusters
- M52
- M103
- NGC 663
- NGC 129
- NGC 133
- NGC 146
- NGC 457
- NGC 559
- NGC 654
- NGC 663
In more detail...
The leading star in the constellation is Alpha Cas, or Shedir 4. This is an irregular variable star 5which forms an optical double star6 with a 9th magnitude blue naieghbour star.
Gamma Cas, sometimes called Tsi7, is an unstable blue subgiant8, throwing off shells of gas at unpredictable intervals- its brightness therefore varies between 2nd and 3rd magnitude.
The double star Eta Cas consists of a yellow9 and a red10 component, and is impressively beautiful even when using relatively small telescopes. The two stars are of 3.44 and 8th magnitude respectively.
Iota Cas is good example of a triple star. Looking at the white 4.5 magnitude star with a small telescope reveals an 8th magnitude companion star. The brighter component has a close 7th magnitude companion, but for separation a telescope with an apature of at least 100 mm and a high magnification is needed.
Rho Cas is another variable star, which can be viewed with the naked eye and appears yellow. Its variation period is unknown.
The region is also home to a large number of nebulae and open clusters:
Next to gamma Cas is the diffuse nebula I59, which consists of two fans pointing northwest.
One degree west of alpha Cas is the diffuse nebula NGC 281.
The planetary nebula NGC 7635 makes good viewing even with small telescopes as it has an high total brightness, but appears faint due to its large extension.
Of the local open clusters the two Messier objects M52 and M103 are probably the most well known. The first is shaped roughly like a kidney and contains over 100 stars. It is a good object for small telescopes and binoculars, showing a prominent 8th magnitude star at one edge. The second Messier object has the shape of a fan and at least 40 members 11.
The cluster NGC 457 also deserves a mention as it is one of the brightest in the sky and is an interesting and attractive target for small telescopes; the stars seem to follow a chain- like structure.
Another star which makes for good viewing is phi Cas, a 5th magnitude yellow supergiant12.
