Compelling Capella

Have you noticed a bright star in the northeast? It is hard to miss if you glance in that direction after sunset. You have found Capella, the little goat, the 6th brightest star in the sky, and the fourth brightest star visible from Peoria.  Capella and Vega are currently the brightest stars you can see early in evening.
 

Click on image to enlarge. At 6 PM, Capella is low in the northeast. Image Credit: Stellarium and me.

Capella is the brightest star in the constellation Auriga, the Charioteer. It is much brighter than the remaining stars in the constellation, a simple five-sided shape. Can you spot it in the above picture? If you need help, the same image with constellation lines is below. 

Capella is the brightest star in Auriga, a simple five-sided shape in the stars. Can you spot it? Image Credit: Stellarium and me.

Like most constellations, the ancient Greeks and Romans imagined a grand story illustrated in this simple shape. They saw a chariot driver, holding a goat and her kids!  Capella is Latin for 'little she-goat'. The the fainter stars that make a triangle with Capella are often called the kids, and are represented as baby goats in constellation images. In some versions of the tale, the charioteer represents Erichthonius, a famed king of Athens. With unparalleled skill in horse training, Erichthonius was the first to hitch a team of four horses to a chariot, imitating the four-horse chariot that pulled the Sun. This feat earned him the respect of Zeus and a place in the stars. Not much is said for why he is holding a goat and her kids. 
 

Auriga the Charioteer, holding his goats. Image Credit: Stellarium and Me

Although it looks like one point of light, Capella is actually a double binary system with 2 pairs of stars orbiting one another. The bright pair is made of two G-class, yellow giant stars with a similar surface temperature to our Sun, but larger and nearing the ends of their stellar lifetimes. The other pair is made of much fainter, relatively cool red stars. The whole system is pretty close to the Sun, only 42.8 light years away (a light year is approximately 6 trillion miles!).

Auriga as depicted by Johannes Hevelius, who created my favorite set of constellation images, all available online.

So look up on the next clear night, and I bet you will find Capella! It is quite bright and hard to miss. Look a little harder and maybe you will be able to find the rest of Auriga. If you have trouble imagining a charioteer in that five sided shape, create your own constellation. 

Stop by the Dome Planetarium at the Peoria Riverfront Museum to learn more about what you can see in the night sky, or take a tour of the Solar System. Shows are always included with general museum admission. And don't miss Wine and Cheese Under the Stars, coming up this December 4!