Most stars are single, like the Sun, or double, like Sirius, the brightest star in the night sky. A few, though, consist of three stars or even more. And the nearest quadruple system to Earth shines dimly in the southern sky on June nights. Gliese 570 is just 19 light-years away. It consists of three full-fledged stars and one failed star. The brightest member of the system is an orange dwarf — a star that’s cooler and fainter than the Sun. Despite its proximity, though, it emits so little light that it’s just barely visible to the unaided eye. Two red dwarfs orbit the main star. Red dwarfs are the most common stars in the galaxy, but they’re also the least impressive. They’re bare cosmic embers that are so faint that not a single one is visible to the eye alone. The red dwarfs in Gliese 570 are several times farther from the orange star than Pluto is from the Sun. The system’s fourth member is a brown dwarf. It was born with so little mass that it couldn’t sustain nuclear reactions in
