Jimmy Westlake: Auriga the Charioteer
December 17, 2006
What’s that flashy golden star hovering over the northeastern mountains as darkness falls in mid-December? It’s Capella, the third brightest star visible in Colorado. Capella is the brightest star in the constellation Auriga the Charioteer, formed by a conspicuous pentagon of five stars.
Auriga represents the mythological character Erichthonius, who was born lame and invented the four-horse chariot so he could get around more easily. In the sky, he is shown holding a nanny goat and her three kids under his arm. The star Capella represents the nanny goat and a distinctive little isosceles triangle of stars close by represents “the Kids.”
From a distance of 42 light years, Capella shines with a yellow color almost identical to that of our own star, the Sun, but the nanny goat is hiding a secret that only modern astronomers have been able to reveal. Capella is really two yellow giant stars in a close orbit around each other. The stars are separated by about the same distance between Venus and the sun, and they whirl around each other once every 104 days. Much farther out, a pair of dim red dwarf stars orbits around the pair of yellow giants with a period of several thousand years. Capella is a wonderful example of a quadruple star system. To the naked eye, however, she gleams as a single star.
Capella is the closest first-magnitude star to the north celestial pole and, as such, always remains above the horizon for folks living north of 44 degrees latitude, about the latitude of Yellowstone National Park. For Coloradans, Capella hides behind our northern mountains for a short time each day before rising again in the northeast.
The star Elnath at the southern-most corner of Auriga’s famous pentagon of stars actually belongs in the neighboring constellation of Taurus the Bull, but has always been associated with Auriga. To the ancient sky watchers, this star represented both the foot of the Charioteer and the horn of the Bull. Modern astronomers found this situation unacceptable and officially gave Elnath to Taurus.
Auriga is chock full of interesting celestial objects. Within his borders lie three beautiful star clusters, known by their Messier catalog numbers, M36, M37 and M38. They are visible to the unaided eye on a dark, clear night, but use binoculars or a small telescope for the best view.
Recommended Stories For You
The star at the top of the triangle marking “the Kids” is a most unusual object. Known as Epsilon Aurigae, the star holds the record for the eclipsing binary star with the longest time between eclipses, just more than 27 years. For comparison, the nearby “Demon Star,” Algol, has an eclipse every 2.9 days. What’s even more remarkable is the duration of Epsilon’s eclipse – 670 days, or nearly two years. Whatever it is that eclipses the main star must be gigantic in size to cover it up for so long. Try as they might, astronomers are unable to determine the exact nature of the eclipsing object. The next eclipse of Epsilon Aurigae is due to begin in spring 2009. You can bet that telescopes all over the world will be watching to learn the secrets of Epsilon’s strange eclipses.