The Sun has been shining for 4.6 billion years.
Longer than Earth has existed. Longer than life has crawled, walked, or wondered. Every day of every year of every millennium, it has risen faithfully, pouring light and warmth into the solar system.
But nothing lasts forever.
In about 5 billion years, the Sun will begin its final act - and it will not go quietly.
The Slow Fade
Right now, the Sun is in its main sequence phase - a stable, middle-aged star calmly fusing hydrogen into helium in its core. It's been doing this for billions of years, and it will keep doing it for billions more.
But hydrogen isn't infinite.
Eventually, the core will run low. And when it does, gravity will take over. The core will contract, heat up, and ignite a shell of hydrogen around it. The outer layers will begin to expand.
Slowly at first. Then dramatically.






