Stellar Landmarks

StarDate: July 4, 2009

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To find your way around the sky, you could use the system of coordinates that astronomers use. They're based on a grid of lines that are like the lines of latitude and longitude on Earth. Using these coordinates, you can find any star or galaxy.

Most of us, though, would rather find our way with the help of landmarks -- whether it's highway intersections on Earth, or prominent stars in the sky.

Tonight, you can use one of the night sky's most famous landmarks to find several prominent stars. These, in turn, can help guide you to even more treasures in the night sky.

At nightfall, the Big Dipper stands in the northwest, with its bowl spilling toward the horizon.

If you line up the two stars that form the outer edge of the bowl, then follow that line to the right, you'll come to Polaris, the North Star. Despite its reputation, Polaris isn't all that bright. But with the Dipper pointing the way, it's fairly easy to find.

Go in the opposite direction to find two other prominent stars. Follow the curve of the Dipper's handle away from the bowl to find one of the brightest stars in the night sky: yellow-orange Arcturus. Then slice toward the south for blue-white Spica. The rule for finding these stars is "Arc to Arcturus, and spike to Spica."

The Big Dipper, the North Star, Arcturus, and Spica give you a good set of landmarks for finding your way around the sky on this Fourth of July night -- and many other nights as well.

Script by Damond Benningfield, Copyright 2005, 2009

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

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