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Planetary nebula
type of emission nebula / From Wikipedia, the free encyclopedia
A planetary nebula is a nebula that is made up of gas and plasma. They are made by certain types of stars later in their life. They look like planets through small optical telescopes.[1] They do not last for long compared to a star, only tens of thousands of years.
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At the end of a normal-sized star's life, in the red giant phase, the outside layers of a star are ejected. Because the outside is gone, the star shines brightly and is very hot. The ultraviolet radiation given off by the center of the star ionizes the gas and plasma that was thrown out from the star. This is what causes a planetary nebula to look like it does.
While some planetary nebulae look similar, others have very distinct and unique shapes. Scientists are not sure why planetary nebulae can look so different from one another. Scientists think that binary stars, stellar winds and magnetic fields might be some of the reasons planetary nebulae can look so varied.[2] In the early 21st century some astronomers began calling them “globular nebulas” to avoid confusing them with the protoplanetary nebulas that make planets.