Question

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

Answer 1

Hint:The mass of a star determines its cycle of life. The life cycle of stars becomes shorter as its mass grows greater. When a star, such as the Sun, burns out or loses all of its hydrogen and forms helium, it will rearrange itself forming the ‘red giant’. But approximately ten billion years are required to complete this process.

Complete answer:
The sun, like every other star, is not really a mass of solid. So, the sun is composed primarily of hydrogen as well as helium layers, almost completely.When the entire hydrogen within the star has been converted to helium (after around five to ten billion years, it shall vary according to the size of that star), there would no longer be enough strength to prevent the star from collapsing, therefore gravity takes control and draws in the star towards itself.

This mechanism now generates enough energy to prevent the star from collapsing and actually forces the star's outermost layers away, thus leaving the star much bigger than it was originally. The star has grown into a Red Giant.The Sun will grow larger and heavier after it transforms into a Red Giant.At this stage, it will begin converting Helium into Carbon for another few hundred million years before it burns out the Helium completely.

Then it will not have enough density to create other heavier elements such as Iron, as a result of which the fusion process will cease, causing the star to collapse at its center (due to the gravity that acts inward because for stabilization there will be no Fusion energy).During this stage, gradually the sun will release its outer layers into space, forming a Planetary Nebula.

Note: 'Planetary nebula' has no relation to planets, despite its name, and they were so called because early astronomers thought it resembled the planets whilst viewing from a small telescope. The Dumbbell Nebula, \[M27\], which was found in \[1764\] by Charles Messier is known to be the first ever 'planetary nebula'.