Here's why:
* Main Sequence: The sun is in the main sequence phase of its life cycle. This is the longest and most stable phase where it fuses hydrogen into helium in its core, producing energy that makes it shine.
* Red Giant: Stars become red giants after they have exhausted their hydrogen fuel. Their core contracts and heats up, causing the outer layers to expand and cool, giving them a reddish appearance.
* Supergiant: Supergiants are much larger and brighter than red giants. They are the final evolutionary stage for massive stars, having already gone through a red giant phase.
The sun will eventually become a red giant, but this won't happen for another 5-7 billion years!
