Similar to humans, stars are born, they live, and they too, die. The sun is no different, and Earth goes with it. But our home planet won't go out so peacefully.
The time period is long - roughly five billion years from now, at least.
As the sun ages, it's getting brighter and brighter, and in as little as a few hundred million years, Earth will get too hot to bear.
Our atmosphere will be stripped off. Our seas are going to evaporate. For a while, we're going to look like Venus, trapped in a choking carbon dioxide atmosphere.
And things will only get worse from there.
In the final stages of hydrogen fusion, our sun will expand and expand, becoming warped and bloated - and red. The red giant sun is sure to devour Mercury and Venus. It may or may not spare Earth, depending on how massive it is. But if the outer atmosphere of the sun enters our planet, Earth will melt in less than a day.
But even if the sun's growth ceases, it's not going to be pretty for Earth still. The extreme energies produced by the sun would be intense enough to vaporize rocks, leaving behind nothing other than Earth's solid iron core.
Neither would the outer planets enjoy the increased radiation output from the sun. The rings of Saturn are composed of almost pure water ice, and the future sun will simply be too hot; it would melt those icy rings.
At first, the intensified radiation would blow out the four outer planets, taking out their atmospheres. But as the sun begins to expand, some of the outer tendrils of its atmosphere may make their way to the giants, passing through the funnels of gravity. Feeding on that stuff, the outer planets will gorge themselves, becoming far larger than they have ever been before.
But wait, there's more. In the sun's final stages, it will repeatedly swell and compress, pulsating for millions of years. This is not its most stable condition, gravitationally speaking. The disturbed sun will drive and drag out the outer planets in strange ways, possibly forcing them into a lethal hug or kicking them out of the system.
For a couple hundred million years, the outer regions of our solar system would be a decent place to call home. With too much heat and radiation coming out of the red giant sun, the habitable zone will move outward.
But finally, our sun will give up its fight, shrugging off its outer atmosphere in a series of outbursts that leave only the center of the star: a white-hot lump of carbon and oxygen.
Initially, this white dwarf is going to be phenomenally hot, blowing off X-ray radiation that will do brutal harm to life as we know it. But within a billion years or so, the white dwarf would cool down to more stable temperatures and merely hang out for trillions and trillions of years.
The dim white dwarf is going to host a new habitable zone, except since the former sun is going to be too cool, the zone is going to be extremely close, far closer than Mercury is orbiting our sun today.
At that distance, any world (or planetary core) will be susceptible to tidal disruption - a nice way of stating that the gravity of the white dwarf could unintentionally rip an object to shreds.
