Here's a breakdown of the stages:
* Main Sequence: This is the longest stage of a star's life, where it fuses hydrogen into helium in its core. The Sun is currently in this stage and will spend about 10 billion years here.
* Subgiant Branch: Once the hydrogen fuel in the core runs out, the star starts fusing hydrogen in a shell around the core. This causes the star to expand and cool, becoming a subgiant.
* Red Giant Branch: The core continues to contract and heat up, eventually reaching a temperature where helium fusion can begin. This causes a rapid expansion and cooling, turning the star into a red giant.
* Top of the Red Giant Branch: This is the point where helium fusion in the core begins, marking a significant milestone in the star's evolution.
Therefore, the total time from main sequence to the top of the red giant branch for a Sun-like star is roughly 10 billion years.
