After the main sequence, the Sun will enter the red giant stage. This is when the Sun will start to run out of hydrogen fuel and begin to expand, becoming much larger and cooler.
Here's a simplified timeline:
* Main sequence: Currently, where the Sun is fusing hydrogen into helium.
* Red giant: The Sun will expand significantly, engulfing Mercury, Venus, and possibly Earth.
* Planetary nebula: The outer layers of the Sun will be ejected, creating a beautiful nebula.
* White dwarf: The core of the Sun will remain as a dense, hot white dwarf.
So, to answer your question directly, the Sun will enter the red giant stage after the main sequence.
