Question

In the life cycle of the star, how does a red giant become a planetary Nebula?

Answer 1

Hint: In order to understand the given problem we must know Nebula and red giant.
Red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution.
Nebula is a giant cloud of dust and gas in space.

Complete step by step answer:
Nebula:
A nebula is a giant cloud of dust and gas in space. Some nebulae come from the gas and dust thrown by the explosion of dying stars, such as a supernova. Some nebulae are the regions where new stars are beginning to form.

Red Giant:
A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The appearance of the red giant is from yellow-orange to red, including the spectral types K and M but also class S stars and most carbon stars.

Generally, a red giant is formed when a star consumes all of its hydrogen to helium and then rearranges itself. This process takes around 10 billion years for stars to become red giant and after becoming red giant , it will start burning helium to carbon for a few 100 years, till it runs out of helium. As there will be no helium, red giant will become less dense, no fusion reaction will take place and the red giant will begin to collapse, because of no gravity. Likewise the outer layer of the red giant will be shed as the Planetary Nebula.

Note: At present our sun is not a red giant , about five billion years from now scientists believe that our sun will become a red giant. Sun will become about 200 times bigger in diameter than it is now. It will become so big that it will engulf Venus, Mercury and possibly even Earth as well.