In five billion years the sun is going to blow up into a red giant, then collapse back down again into a white dwarf - a dying star roughly the same size as Earth itself. All of the solar system planets up to, and including, Earth will probably be vaporised during this stellar ballooning. We'll be long gone (hopefully to another part of the universe, rather than gone gone).
But what will happen to Earth itself? White dwarfs stay in that state for a long time. After an initial fast cooling phase, they cool much slower and could remain stable for billions of years. Perhaps even long enough for life to arise once more in our solar system, if a planet survived, and the conditions were right...
And they could be. I have an article in this week's New Scientist magazine about a new paper (on arXiv) by Luca Fossati at the Open University, UK, and colleagues. Fossati and his colleagues modelled what the light from a white dwarf would look like once it reached an Earthlike planet in the habitable zone around a white dwarf, and what the implications are for the possibility of life in a white dwarf star system. You'll have to go and read the full article for the details... but I'm optimistic.
