Auriga the Charioteer

© 2001 by Robert C. Moler

The first winter constellation to appear is also the last to disappear in the spring. This constellation is Auriga the charioteer. It is the most northerly of the winter constellations. In fact its northern stars don't set for those observing Northern Michigan.

Auriga depicts a Charioteer, who is crouched down and holding a nanny goat and her three kids. One could see driving a chariot, while trying to hold all those goats, could be hazardous undertaking. Perhaps after the crash the gods placed him in the heavens to warn other distracted drivers.

Basically, the stars of Auriga form a pentagon, with the slim triangle asterism of The Kids on the right side. Auriga's brightest star is Capella, the 6th brightest night time star at magnitude 0.08.

Even on late summer evenings, Capella can be seen scraping the northern horizon with the promise of the return of winter. As it slowly rises in the northeast in the autumn, it has been the source of UFO calls. Capella is actually a binary star some 42 light years away. Each of the stars is much brighter than the sun, but nearly the same color as our star. The stars are less than the earth's distance from the sun apart, and orbit each other in 104 days.

The name Capella means Little She Goat. Her kids are nearby. The Kids is an asterism, that is, an informal constellation, like the Big Dipper and the Belt of Orion. The most interesting star of the Kids is Epsilon Aurigae.

Epsilon is a most interesting eclipsing binary star. Most eclipsing binaries have periods in terms of days. The period of Epsilon is 27 years, and the eclipses last nearly 2 years. The partial phase of the eclipse lasts 4 months each at the beginning and end of the eclipse. The last eclipse was in the period 1982-84. The next eclipse will occur in 2009-11. The depth of the eclipse dims the star by 0.8 of a magnitude.

Another one of the Kids is an eclipsing variable star. It is Sadatoni or Zeta Aurigae. It normally shines at 5th magnitude, but during the 40 day long eclipses it dims by half a magnitude. The partial phase of the eclipse lasts about 32 hours on each end of the eclipse. The period of the eclipses is 2.66 years.

There's a third eclipsing binary in Auriga. It is Menkalinan or Beta Aurigae. It has a very short period compared to the others, only 95 hours, just under 4 days. The stars are nearly identical in mass and type so there is nearly an identical dip in magnitude when each is eclipsed by the other. The magnitude dips are small, only a tenth of a magnitude., and last less than 10 hours.

Auriga lies along the Milky Way, and as such contains galactic star clusters and nebulae. The three star clusters M36, M37 and M38 are all great telescopic objects. They can also be spotted with binoculars as fuzzy spots. M37 and M38 are the richest of the three in number of stars.

For those wanting to explore deeper in Auriga, Check out Burnham's Celestial Handbook and a good set of star charts.

One of those faint wonders in Auriga is the star AE Aurigae, a massive blue-white variable star with a high velocity. It and the stars Mu Columbae (in Columba the dove) and 53 Arietis (in Aries the ram) seem to be fleeing the star forming region in the constellation of Orion. AE Aurigae has small irregular fluctuations in brightness. It appears to be located in a nebula, though it may only be passing through it. The nebula IC 405, appears vastly different in photographs in red and blue light. The red light photographs pick up the light of hydrogen, while those in blue emphasize the reflection of AE's light by dust grains. A similar blue nebula surrounds the stars of the Pleiades. It's a challenging object for the amateur's telescope.

Auriga may not be the splashiest winter constellation, but it contains many interesting wonders well worth study.

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Updated: 01/01/01