In one possible scenario, there are two stars approximately the same size—let's say about the size of our sun. At a certain point in their lifetimes, each star will expand into a red giant ...
A newly discovered planet offers new insights into the Solar System after ... the end of its life. "When the Sun reaches its Red Giant phase, it will expand out roughly to the orbit of Earth.
When they reach the end of their long evolutions, smaller stars—those up to eight times as massive as our own sun ... to expand outward. At this stage, the star becomes a large red giant.