When a Star Becomes a Red Giant

What happens when a star becomes a red giant?

When a star becomes a red giant, what will it do?

Answer:

A star becomes a red giant when its core contracts, but the outer layers expand due to hydrogen fusion, resulting in the star's expansion and cooling.

When a star evolves from the main sequence stage to become a red giant, its core contracts but the outer layers expand due to hydrogen fusion in a shell outside the core. This expansion and increase in luminosity is a consequence of the change in the star's interior composition. Therefore, option a) expand and cool precisely represents the transition of a star into a red giant. This expansion leads to a larger, redder, and more luminous star, which also results in a decrease in surface temperature.