The Sun is the most important star in our galaxy, and at some point, it’s going to die. When that happens, it’ll turn into a red giant, getting so big it’ll swallow Mars, Mercury, and quite possibly vaporize our own planet. Don’t panic yet, we’ve got a billion years to prepare before the big red comes.
Stars have a life cycle just like us: they are born, they live, and then they die.During their lives, stars need to have a strong core, one that can fuse hydrogen into helium to make nuclear fusion. Stars will work their cores for billions of years. But eventually, they’ll run out of hydrogen for their fusion process. When that happens, the star can't hold up against gravity and its core will start to collapse. The core will get smaller and denser, while its outer shell expands and cools, giving a distinctive red hue. The combination of “cooling” and “expanding” is where the name red giant comes from.
Red giants are huge, reaching sizes of 100 million to 1 billion kilometers in diameter, or 62 million to 621 million miles. That’s nearly 1,000 times the size of the sun. So when our sun turns into a red giant, life as we know it will cease to exist. But there is an upside to this. When stars morph into red giants, they change their habitable zone. The habitable zone is a region with the right conditions for life. So as the Sun gets larger and redder, it’s warmth will extend to the outer reaches of our solar system. Making it possible for life to begin on a whole new planet.