At the present time, the Sun is over four billion years old—approximately half-way through its expected life span. In another 4 to 5 billion years, the culmination of 8-10 billion years of nuclear fusion will see the Sun swell into a red giant, before shrinking into a white dwarf.
Although we won’t be around to see the Sun die a woefully underwhelming death (at least compared to its larger counterparts), we can study stars within the same size threshold to get a glimpse of what the future has in store for our local star.
In that sense, Mira A—a red giant that lurks around 400 light-years from Earth—is a good case study. The only difference is, Mira A is part of a binary star system, meaning it has a sibling nearby (as do most star systems). The companion, called Mira B, orbits Mira A from a distance that’s about twice as far as Neptune is from the Sun, what’s more is that Mira B has already progressed beyond the main sequence phase of stellar evolution.
In a new(er) image from ALMA, the relationship this duo shares is clearer than ever before. From the ESO: