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Changing Skies

February 24, 2011

Nothing lasts forever -- not even the stars, and certainly not the patterns of stars that decorate our night sky.

The stars themselves will vanish over periods of millions or billions of years. But the star patterns -- the connect-the-dots constellations -- will disappear much more quickly. The timescale is long by everyday standards -- no constellation has changed significantly during all of human civilization -- but pretty short on the timescale of the universe.

Consider the most famous star pattern of all, the Big Dipper. This grouping of seven stars has figured in the starlore of just about every culture on the planet. It was seen as everything from a great bear to a plow to a drinking gourd.

In the distant future, though, gourd, dipper, and plow will all vanish, because the stars are moving in different directions.

The five stars in the middle of the dipper are actually moving through space as a group; more about that tomorrow. But the stars at the tip of the handle and the outer edge of the bowl are moving down and to the right compared to the others. So a hundred thousand years from now, the bowl will form a long wedge, while the handle will have a spike at the end. This new pattern will look less like a dipper and more like a hand vacuum.

For now, though, enjoy the dipper as it wheels across the north. It's in the northeast this evening, standing on its handle, and high in the northwest at first light.


Script by Damond Benningfield, Copyright 2010


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