A close companion can really stir things up. Consider the star system R Sculptoris. It’s in the faint constellation Sculptor, which is low in the south at nightfall. The system’s main star is probably heavier than the Sun. And it’s at the end of its life. Changes in its core have caused the star to puff up like a giant balloon. Those changes also cause the star to produce outbursts of hot gas. In fact, one of those outbursts probably took place almost two millennia ago. It happened when the star suddenly started fusing helium atoms in a layer around the star’s core. That produces a lot of energy, which can cause some of the gas at the star’s surface to pulse out into space. In the case of R Sculptoris, the pulse lasted a couple of hundred years. If R Sculptoris were a single star, then the pulse would expand evenly, like a growing soap bubble. Instead, though, the star appears to have a small companion. The two orbit each other once every 350 years or so, which means they’re a good dis
