“Alpha Librae” is a perfectly good name for a star. It tells us that it’s in Libra, the balance scales. It also tells us that it’s either the constellation’s brightest star, or that it’s in a special location. In this case, it’s the location — it’s the starting point for a diamond-shaped pattern of stars.
But Alpha Librae doesn’t have nearly the cachet as an older name for the star: Zubenelgenubi. That name comes from an Arabic phrase that means “the southern claw.” At the time the name was bestowed, the star represented the southern claw of Scorpius. Later skywatchers created Libra from Zubenelgenubi and several other stars of the scorpion.
The star itself probably warrants the attention that comes with the name. It consists of at least four stars, which are split into two pairs. The pairs are separated by more than 500 billion miles. That’s far enough apart that we see them as separate pinpoints of light.
That’s not the case with the individual stars in each pair. They’re so close to each other that their light blurs together. When astronomers break down the light from each pair, though, they see the “fingerprints” of two stars — giving the southern claw a total of at least four stars.
Zubenelgenubi huddles close to the Moon late tonight. They’re in the south at first light tomorrow, with Zubenelgenubi close to the right or upper right of the Moon.
We’ll talk about the Moon and the heart of the scorpion tomorrow.
Script by Damond Benningfield