Let's start 650 light years way, in the direction of the constellation Aquarius. There's a star there that is decidedly odd. Called R Aquarii*, it's the swollen hulk of a star that was once much like the Sun, but is now nearing the end of its life. Complicated processes in the core have dumped huge amounts of energy into the outer layers of the star, and when you heat up a gas it expands. But, it gets so big that the amount of energy it emits per square centimeter actually goes down, so its temperature drops as well. Cooler stars emit redder light, so we call these stars red giants.