February 27th, 2016
(Click on an image above to enlarge it.)
With the Moon now past full and moving into the morning sky, now’s a good time to enjoy some of the winter constellations still shining brightly in the mid-evening sky. Observers in the United Kingdom and North America can go outside at around 8pm and still see Auriga riding high in the skies above.
Auriga, the Charioteer, is thought to represent Erichthonius, the lame footed king of Athens who invented the chariot as a means of transport.
It’s a mis-shapen hexagon halfway between Perseus and Gemini, easily visible throughout the entire winter and made distinctive by its brightest star, Capella.
Not only is Capella the brightest star in the constellation, but at magnitude 0.1, it’s also the sixth brightest in the entire night sky.
Like many other bright stars, at just under 43 light years, Capella is one of our closest neighbors but its most fascinating feature is invisible to us. To the naked eye it appears as a single star but it’s actually a quadruple system made up of two pairs of stars.
The first pair are two yellow stars, similar to the Sun but each about 2-3 times more massive. They orbit one another once every 100 days or so with a gap of about ¾ the distance of the Earth to the Sun between them.
The other pair consists of two red dwarfs, thousands of times further out from the first pair.
Capella is also one of the few stars that has its own mythological associations.
According to Greek myth, the star represents the she-goat Amalthea who nursed the baby Zeus.
If you look closely at Capella you’ll see a small elongated triangle of three stars, just to the east and on the Perseus side of the constellation.
Known as the Haedi (or “the kids”) the bottom two stars represent the young goats sometimes depicted in the arms of the charioteer himself.
The northernmost star in the triangle may also be worth a look. Epsilon Aurigae is a variable star; in other words, it appears to grow dim and then brighten again. Unfortunately, it doesn’t happen very often – in fact, it only happens to Epsilon once every 27 years and it won’t happen again until approximately 2036.
At that time, the star will appear to fade from magnitude 3.0 to 3.8 and will stay this way for about a year or so. This is because the star is actually a binary system. Once every 27 years the fainter companion passes in front of the brighter primary star and eclipses it, causing the star’s magnitude to drop.
Auriga, like Andromeda, actually shares one of its stars with another constellation. If you look carefully at the chart above, you’ll notice that the southernmost star, El Nath, is also a part of Taurus the Bull.
Once known as Gamma Aurigae, it now officially belongs to only Taurus and is known as Beta Tauri.
Adapted from the forthcoming book A Beginner’s Guide to the Constellations – coming soon!
Star charts created using Mobile Observatory for Android devices.
Easy Things to See With a Small Telescope
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