The full Moon achieves a sort of celestial balance tonight. It’s passing across Libra, the balance scales – a symbol of justice. But the proper names of the constellation’s brightest stars have nothing to do with balance, justice, or anything similar. Instead, the names mean “the claws” – of nearby Scorpius, the scorpion.

Originally, the stars did belong to Scorpius. But thousands of years ago, they were severed from the scorpion and placed in a new constellation.

As night falls, one of the claws stands to the upper left of the Moon. Called Zubenelgenubi, it represents the southern claw. It’s the second-brightest star of Libra, and it’s about 75 light-years away.

Like many of the stars in the night sky, Zubenelgenubi is deceiving. To the eye alone, it looks like a single point of light. Scan it with binoculars, though, and you’ll see two stars. They appear to be moving through space together, so they might be orbiting each other. But they’re so far apart that it takes the light from each star a month to reach the other one. At that separation, they might not be held together by gravity – their close appearance might be just a coincidence.

Each of the two stars is actually a binary in its own right. In both cases, the stars are so close together that even giant telescopes can’t see them as individual stars. But we see the “fingerprints” of two stars in the light from each half of the southern claw.

Script by Damond Benningfield