Big Dipper

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The best-known star pattern in the sky scrapes the northern horizon tonight: the Big Dipper.

The Big Dipper is an "asterism" -- a group of stars that forms an easy-to-see pattern, but that's not a constellation in its own right. It forms the body and tail of the constellation Ursa Major, the big bear.

The dipper's seven prominent stars are all easy to see -- even from light-polluted cities. Five of these stars were born together, from the same cloud of gas and dust, and they still move through space together. They're about 80 light-years from Earth.

To see the Big Dipper, you don't need binoculars or a telescope. Instead, just head outside around eight o'clock tonight. You need a spot with a clear, open view of the northern horizon. From there, you should see the seven stars of the Big Dipper.

It's easy to see why it's called the Big Dipper: it's a huge celestial pattern. Four stars form the dipper's bowl, while the other three mark its handle. The second star from the handle's end is double. Most people can see both stars, although binoculars help them stand out.

Using the Big Dipper, you can easily find the North Star. Look at the two stars on the far right of the bowl. Draw a line from the bottom star to the top star. Follow that line until you come to a star that's as bright as they are, but much higher in the sky. That's Polaris, the North Star. It marks true north -- a guiding light in the night sky.

Script by Ken Croswell, Copyright 2008

For more skywatching tips, astronomy news, and much more, read StarDate magazine.