Red Giant Star - The Onset Of Gianthood, Events During Gianthood
core fuel fusion hydrogen
A red giant is a star that has exhausted the primary supply of hydrogen fuel at its core and is now using another element such as helium as the fuel for its energy-producing thermonuclear fusion reactions. Hydrogen fusion continues outside the core and causes the star to expand dramatically, making it a giant. Expansion also cools the star's surface, which makes it appear red. Red giant stars are near the end of their lives, and die either in a supernova explosion, or more quietly as a planetary nebula. Both fates involve the expulsion of the star's outer layers, which leave behind the small, exposed core.
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Stars are self-gravitating objects, meaning that they are held together by their own gravity. A star's gravitational field tries to compress the star's matter toward its center, just as Earth's gravity pulls you toward its center. Since stars are gaseous, they would shrink dramatically if it were not for the thermonuclear fusion reactions occurring in their cores. These reacti…
Helium-fusing stars have found a way to maintain themselves against their own gravity, but there is a catch. The amount of energy a star gets out of a particular fusion reaction depends on the binding energy of the elements involved. When the helium is exhausted, the cycle just described begins anew. The core contracts and heats, and if the temperature rises to 600 million kelvin, the carbon will…
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