Monday, December 31, 2007

Gamma Cassiopeia

(Click to enlarge)

Floating in a sea of stars that is our own Milky Way Galaxy lies the Gamma Cassiopeia Nebula (IC 59/63). This is an object that is not imaged very often and is very dim. A narrow band Hydrogen Alpha filter allows us to see more of this emission/reflection nebula due to the energized Hydrogen gas from the radiation emitted from the nearby star, Gamma Cassiopeia. The front edge of the nebula takes the brunt of the stars radiation and glows red, while the blue area behind the front, is simply reflected and refracted light.

Gamma Cassiopeia is the middle star of the well-known “W” asterism of Cassiopeia in the autumn sky. This hot, blue, Class B star is an eruptive variable, which means it will vary in brightness from about 1.6 magnitude to about 3.0. Gamma Cas is about 40,000 times more luminous than our sun (including the ultraviolet radiation from the 25,000 Kelvin surface) and about 15 times more massive. One of the very peculiar aspects of this Be class star is that it rotates at about 300 kilometers per hour at its equator. This is 150 times faster than our suns rotation. This rotation, along with the size of the star, is believed to cause a “decretion” disk. Mass is lost from the rapidly spinning star and forms a disk around the star. It is believed that this disk contributes to the variation in luminosity.

Image Acquisition information:

Date: December 2007
Location: Star-lodge Observatory
Scope: FSQ 106
Camera: STL 11000
L(Ha)R(Ha)GB 100:40:60:60:60

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