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NGC 7635 ia a nebula in Cassiopeia constellation, also called "Bubble Nebula" because of its shape.
It is an HII region, at whose southern vertex there is an empty structure, caused by the pressure of the radiation of a central blue star, whose stellar wind reaches 2000 km / s; it is a blue giant, which is also responsible for the ionization of the nebula, which then emits its own light. Its distance from the Sun is estimated at 11,000 light years.
