Caph and Ruchbah
September 02, 2016
Featured above are Caph at magnitude 2.27 (top) and Ruchbah at magnitude 2.66 (bottom), the second brightest and third brightest stars, respectively, in Cassiopeia, the familiar W-shaped, circumpolar constellation on the other side of the North Star from the Big Dipper. Though it can be seen all year long by viewers in the Northern Hemisphere, Cassiopeia is highest in the sky during the autumn season, and what can be immediately seen in these images is that the Cassiopeia region has more than its fair share of open clusters.
Caph (Beta Cassiopeiae), classified as a yellow giant star, is approximately 3 times as large as the Sun and lies about 55 light years from our solar system. The orange colored smudge just to the left of Caph is dwarf galaxy IC10 at magnitude 11.2. At the 5 O'clock position below Caph is what at first sight looks like a large globular cluster. Instead, this is the highly impressive open cluster NGC7789. Its claim to fame is a highly variable variable-star that sits at the southwestern edge of the cluster. In fact, its variability is so huge it could be mistaken for an alien beacon (see EPOD for February 10, 2009).
Ruchbah, (Delta Cassiopeiae), 100 light years away, is the main star in an eclipsing binary system that orbit each other every 759 days. There are a number of very well-known deep-sky objects in this frame. The closest open cluster to Ruchbah at the 1 O'clock position is Messier 103, go a little further out in the same direction and the larger open cluster you come to is NGC663 or Caldwell 10. Drop below Ruchbah to the 5 O'clock position and you come to the famous ET or the Owl cluster, NGC457, or Cadwell 13. Move to the right-hand edge of the frame and the very bright star there is Gamma Cassiopeiae (strangely it doesn't have a common name) and in the top left quadrant between the star spikes you can see the Gamma Cassiopeiae nebula, IC59, also called the Ghost nebula.
Open up your favorite planetarium program and see how many deep-sky objects you can discover in these two wide-field images.
Photo Details: Two-frame mosaic of Caph; and a two-frame mosaic of Ruchbah. Each individual frame is 12 x 10 minutes; using the Canon 200 mm prime lenses at f/3.8 and the Trius 10-Megapixel M26C OSC CCDs. The field of view of the mosaic is approximately 7 degrees x 7 degrees.