In about 5 billion years, the Sun will die a spectacular death.
As its hydrogen runs out, it will begin to burn helium. The Sun will become a red giant, stretching out to where Venus orbits today. Once the helium is used up, the Sun will collapse. It’ll become a hot white dwarf star about the size of Earth. Then it will cool.
We know all this from watching other stars. Point a telescope in just about any direction, and you’ll see some star’s birth or death in progress. Recently, scientists have discovered that some stars have planets spinning around them, just as our star does. Perhaps somewhere, there’s a planet where creatures are wondering, “Who’s out there?”