* Expansion and Temperature Increase: When the Sun runs out of hydrogen fuel in its core, it will start fusing helium, causing it to expand dramatically. This expansion will engulf the orbits of Mercury, Venus, and likely Earth.
* Increased Solar Radiation: The Sun will also become significantly hotter, radiating much more energy. This intense heat would bake the Earth, vaporizing all water and rendering the planet uninhabitable.
* Gravitational Effects: The Sun's expansion would also disrupt the orbits of the planets, potentially flinging Earth out of the solar system altogether.
Timeline: This event is still billions of years away, as the Sun is roughly halfway through its main sequence lifetime. However, it's a certainty in the Sun's evolution, and a stark reminder of the finite lifespan of stars.
The Good News: While Earth's fate is sealed, the Sun's expansion won't happen for billions of years. This gives humanity plenty of time to explore the universe and potentially find a new home.
