Sun
Earth's fate is still a bit of a mystery. In the long term, the Earth's future depends on the Sun, and the Sun is going to be fairly stable for the next 5 billion years.  Calculations suggest that the Earth might move to a wider orbit. This is because about 30% of the Sun's mass will blow away in the solar wind. However, in the very long term the Earth will probably be destroyed as the Sun increases in size. Stars like the Sun become red giants at a later stage. The Sun will expand beyond orbits of Mercury, Venus, and probably Earth. In any event, the ocean and air would have vanished before the Sun gets to that stage.