What will our Sun eventually become?

The answer

In about 5 billion years, the Sun will exhaust its hydrogen fuel and expand into a red giant, engulfing Mercury and Venus and possibly Earth. It will then shed its outer layers into a spectacular planetary nebula while its core contracts into a white dwarf - an Earth-sized ember of carbon and oxygen with a density so great that a teaspoonful would weigh several tons. Over trillions of years, the white dwarf will slowly cool and fade, eventually becoming a hypothetical 'black dwarf,' though the universe isn't old enough for any to exist yet.