Thursday, August 28, 2008

Crowning Glory

Due east of Arcturus, the orange giant star we examined last week, is a pretty, horseshoe-like arrangement of stars. The Horseshoe is the central asterism, or star pattern, of the constellation Corona Borealis (bore-ee-AL-iss) the Northern Crown.

Sometimes called “Ariadne’s Crown”, its legend has been known since at least the 5th century BCE. Ariadne was the mythical princess of Crete, an island in the Mediterranean Sea near Greece. The crown was reportedly a gift from the wine god Dionysus, who loved her.

You may recall the ancient story of the Minotaur, the half-man, half-bull who lived at the center of a labyrinth or maze. This was Ariadne’s gruesome half-brother, to whom seven men and seven women had to be sacrificed each year. It was Ariadne’s magic ball of twine that enabled one of those men, the hero Theseus, to find his way both into and out of the labyrinth so he could slay the Minotaur.

Two star atlas depictions of Corona Borealis

The Grecian crown has been depicted as both a traditional, jeweled crown and a wreath of flowers, but other cultures saw the curved star pattern quite differently. The aborigines of Australia called it the “Boomerang,” and the early Arabs called it the “Beggar’s Bowl.”

Chart created with Your Sky

Under dark skies, away from city lights, you should see seven stars forming the curve of the Horseshoe. The brightest one has two names: Alphecca (ahl-FECK-uh) and Gemma (GHEMM-uh). Alphecca is Arabic for broken one, a reference to the semicircle of stars. Gemma, a star name adopted later, is Latin for jewel. This luminous white star is also known as the “Pearl of the Crown.”

The star to the right (northwest) of Alphecca is Nusakan (nuss-uh-KAHN), the second brightest star in Corona Borealis and a yellow-white dwarf star. Nusakan is from the Arabic for two lines of stars, which has nothing to do with its crown-jewel status but is instead a reference to an ancient Arabic constellation.

Stargazers in the southern latitudes of the country can challenge themselves by looking for the other celestial crown: the faint Southern Crown, Corona Australis (aw-STRAH-liss). You’ll find it hanging beneath Jupiter and the Teapot asterism of the constellation Sagittarius the Archer, low over the southern horizon. As shown below, this crown was sometimes depicted as a wreath of myrtle leaves, a plant closely associated with none other than Ariadne’s main squeeze, Dionysus.

Star atlas depiction of Corona Australis
Courtesy of
Linda Hall Library of Science, Engineering and Technology