The Ghost of Cassiopeia, also known as IC 63, is formed by radiation from the nearby unpredictable variable star Gamma Cassiopeia, which slowly destroys a ghostly cloud of dust and gas. The constellation of Cassiopeia, named after the heroine of Greek mythology, forms in the night sky an easily recognizable form of letter W. The central point of W is the star Gamma Cassiopeia.
The remarkable Gamma Cassiopeia is a blue-white variable star surrounded by a gaseous disk. It is 19 times more massive and 65 thousand times brighter than the sun. The star also rotates at an incredible speed: an imaginary point on its surface will overcome 1.6 million kilometers per hour, which is more than 200 times more than on our star. Rotation causes mass eruption from Gamma Cassiopeia to the surrounding disk. It is the loss of mass that causes the observed changes in brightness.
Gamma Cassiopeia radiation is so powerful that it affects the IC 63 nebula, located a few light years from the star. The hydrogen inside IC 63 is bombarded by ultraviolet radiation from the luminaries, causing its electrons to acquire energy, which they later release as hydrogen-alpha radiation, shown in red in the image below.
The radiation makes IC 63 an emission nebula, but we also see a blue color, which is caused by the Gamma of Cassiopeia reflected from dust particles. This means that the Ghost of Cassiopeia is also a reflective nebula.
The colorful and ghostly nebula is slowly dissipated by the ultraviolet of Gamma Cassiopeia. However, IC 63 is not the only object under the influence of a mighty star. It is part of a much larger region surrounding the luminary, which occupies approximately four times the size of the full moon in the sky.
This area is best seen from the northern hemisphere in autumn and winter. Although it is available for observations all year round, it is very dim, so amateur astronomers need a fairly large telescope and a dark sky.
Being outside the atmosphere of the Earth, Hubble gives us an idea of what we cannot see with our own eyes. This photo is perhaps the most detailed image of IC 63, and it perfectly demonstrates the capabilities of the space telescope.
The Ghost Nebula of Cassiopeia
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