Planetary Nebulae and Supernovae

Planetary nebulae are shells of matter ejected by relatively low mass stars toward the end of their lives. The gas is ionized and made visible by radiation from the stars remaining core. In contrast a supernovae remnant is the gaseous remainder of a star destroyed in a supernova. Supernovae processes can result in the ejection of most of the stars mass and energy and can sometimes be brighter and more energetic than the entire galaxy in which the star resides.