In the life cycle of a star, how does a red giant become a planetary nebula?
1 Answer
After burning up it's fuel.
Explanation:
Basically a Red Giant is formed when a Star like our Sun burns all of it's hydrogen to helium and then rearranges itself. This process takes about 10 Billion years. After becoming a Red Giant the Sun will become bigger and more denser than it is today.
At this time it will start burning Helium to Carbon for a few hundred million years until it runs out of Helium and since it will not be dense enough to form other heavier elements like Iron, the fusion process will stop, making the Star collapse on it's core due to inward acting gravity as there will be no Fusion energy to Stabilize this gravity.
At this time the Sun will calmly shed it's outer layers into Space called a Planetary nebula and become a White Dwarf, a cool extremely Dense Star, about the size of the earth but mass of the Sun.
