Thursday, May 13, 2010

Cup of Stars

In close proximity to the spring constellation of Corvus the Crow— and associated with it in myth— is the constellation of Crater the Cup (KRAY-turr). Both constellations have a central asterism (recognizable star pattern) that aids us in locating them. The Sail asterism of Corvus is the more prominent of the two. Spotting the goblet-shaped asterism nearby is a bit more challenging.

Many cultures have viewed the pattern found in Crater as a vessel: an urn, a goblet, a water bucket, a pot, a mixing bowl for wine, a bowl, or a cup associated with various gods.

Corvus, Crater, and Hydra in John Flamsteed’s 1729 star atlas
Courtesy of
Linda Hall Library of Science, Engineering and Technology

In the Greco-Roman mythological tradition, Corvus, Crater, and adjacent constellation Hydra the Water Snake were intertwined. The crow, sent by the thirsty Apollo to fill a cup with water, was distracted by a fig tree and decided to linger there until the fruit ripened. He returned with a water snake in his claws, claiming it had caused his delay. Apollo saw through the lie and forever banished bird, cup, and water snake to the sky. To the sky!

1) An hour after sunset, face south and locate the Sail asterism of Corvus, just east of the meridian.

Looking south to the Sail of Corvus & the Goblet of Crater
Star maps created with
Your Sky

2) The Goblet asterism of Crater lies just west of the Sail. With the Sail oriented upright on its mast, the Goblet appears to be tipping over toward the Sail. Can you spot it? The stars of the Goblet are dimmer than the four Sail stars and similar in brightness to the mast star, Alchiba (ull-kibb-AH). The bowl of the Goblet is larger in area than the Sail.

3) A star at the bottom of the Goblet’s base is the only one with a traditional name. The star on the right is Alkes (ALL-keess), the second brightest star in Crater. Alkes is from the Arabic for wine cup. An orange giant star, Alkes is about 80 times as luminous as our Sun.

Each time I search for the Goblet, it takes me a little while to find it. Just when I’m convinced I won’t be able to make it out, pop, there it is, a generously-sized cup of vintage starlight. So be patient. And when you find it, drink deeply. Salud!