Neighbors come and go — in space as well as here on Earth. That’s because the stars all follow their own orbits around the center of the galaxy. So a star may sweep past our own solar system, becoming a close neighbor for a while before departing for other neighborhoods. An example is a star system that was discovered in 2013. It’s only 20 light-years away, making it a close neighbor. But not so long ago, it was the closest neighbor — though it would have been too faint to see from Earth. The system consists of a tiny, faint star known as a red dwarf, plus a failed star known as a brown dwarf. It’s been nicknamed Scholz’s Star for the astronomer who found it in observations by a space telescope. Follow-up observations showed that the system is heading almost directly away from us — an indication that it once was much closer. 70,000 years ago, in fact, it passed just eight-tenths of a light-year from the Sun. By comparison, today’s nearest neighbor is five times farther. The system prob
