he bad news is that when our sun finally dies, Earth will be reduced to a ruined lump of iron, if it’s not outright consumed. The good news is . . . well, there is no good news.

All things must come to an end, even our own solar system. But thankfully, we don’t have to sweat about anything in the short term; our sun is still about four to five billion years away from its eventual—and ultimate—demise.

But our solar system is still going to start getting a little rough in the meantime.

An Aging System

All stars, including our sun, fuse hydrogen in their cores; this is how they produce all their heat and light. But the fusion of hydrogen leaves behind a byproduct: helium. As our sun ages through billions and billions of years, more and more helium builds up in the core. This makes it harder for the sun to fuse hydrogen—the helium is literally pollution getting in the way. To compensate for this and remain in balance, the core of the sun gradually grows hotter with time.

See Also:

Gigantic ‘alien’ comet spotted heading straight for the sun

End result: the sun is getting hotter. The dinosaurs knew a smaller, dimmer sun than we do today. Billions of years ago, you wouldn’t even recognize our own star.

Read more: Popular Mechanics