In about 5 billion years, our Sun will run out of fuel and swell into a red giant, engulfing Mercury and Venus. Earth might survive, scorched and lifeless. Billions more years later, the Sun will shrink to a white dwarf, leaving the remaining planets adrift in the darkness. Over time, gravitational interactions with other stars might fling them out of the solar system entirely, leaving behind a cold, lonely husk of what once teemed with life. It's a distant future, but even for our tiny corner of the universe, the story has an end.