Even if you're new to stargazing, no doubt you've seen the seven bright stars that outline the Big Dipper, and this time of year they are easy to find. As soon as it's dark enough after sunset, look high in the northern sky for the upside down Big Dipper.
If you ask the average person on the street to name one constellation, they'll probably look at you funny and say "the Big Dipper." The problem with that answer is that it's wrong. Technically, there is no such constellation as the Big Dipper. Back in the 1930's astronomers from all around the world got together and agreed on a standard set of 88 constellations and the Big Dipper wasn't one of them. So what is the Big Dipper? Astronomers have a five-dollar word for it. They call it an asterism, a distinct pattern of stars, one tiny step below a constellation. You would think the most famous star pattern would rate the title of constellation but it's just an asterism. Sometimes there's just no justice in the heavens!
The Big Dipper, our favorite asterism, is actually the rear end and tail of Ursa Major, the Big Bear. It's the brightest part of the Big Bear, and so high in the sky this time of year you should be able to see the rest of the bear with just a little bit of work, a little bit of imagination, a semi dark sky and comfortable lawn chairs to lie back on.
Look just to the lower left of the pot section of the Big Dipper for three dimmer stars forming a skinny triangle that allegedly outlines the Big Bear's head. That's the dimmest part of the Big Bear so once you've seen that, the rest of Ursa Major should be easy. From that skinny triangle, look to the upper left for two stars right next to each other that should jump right out at you. These are called Talitha and Al Kapra, and they mark the position of the bear's front paw. Between the front paw stars and the triangular head is a star that makes up the bear's knee and once you spot that you've seen one of the front legs of Ursa Major. Unfortunately there are no stars that make up the other front leg. To see that second front leg, you really have to put your imagination in overdrive.
There are two curved lines of stars that outline the Bear's back legs but the one in the foreground is much easier to see than the one that faces away from us. Just look to the upper right of the two front paw stars Talitha and Al Kapra for two more stars right next to each other. Those are Tanis Borealis and Tanis Australis that make up the back paw of the Big Bear. From the back paw you see a line of stars that curves back to the lower right and links up with the pot section of The Big Dipper or the rear end of Ursa Major. Once you've got your eyes around the rear leg of the bear, you've done it. You've just seen the Big Bear, one of the largest constellations in the heavens!
The seven stars that make up the Little Dipper are the same seven that outline the Little Bear, otherwise known as Ursa Minor. The Little Dipper is not nearly as easy to see as the Big Dipper, especially if it's competing with any kind of urban lighting. The best way to see The Little Dipper, or Bear, is to find Polaris the North Star at the end of the handle of the Little Dipper, or the end of the tail of the Little Bear. Polaris is not the brightest star in our sky but a very significant one because it shines directly above the Earth's North Pole. As the Earth spins on its axis once every 24 hours, it appears to us that all the stars in the sky whirl around the North Star in the same period. I call it the "Lynchpin" of the sky. Use Dubhe and Merak, the two bright stars in the pot of the Big Dipper, as pointer stars to Polaris. The North Star should be about three of your fist-widths at arm's length to the lower right of Dubhe and Merak.
Tonight as darkness sets in the Little Dipper will lie below the Big Dipper and will appear to be standing on its handle. Once you find Polaris at the end of the handle, look for two fairly bright stars to the upper right called Kochab and Pherkad. These two make up the far side of the Little Dipper's pot across from the handle. Your mission, and it's not an easy one, is to find the four very dim stars between Polaris and Kochab/Pherkad that make up the rest of the pot and handle of the Little Dipper.
Ursa Major and Ursa Minor, the Bears of the sky, have quite a story in the sky and I'll cover that tale of the tails in next week's Skywatch.
Diagram of the big and little bears...Click