Moon, Regulus, and Saturn

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• 22 of 1970
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The Moon will swoop past the star Regulus and the planet Saturn over the next few nights. Tonight, Regulus and Saturn rise well below the Moon, in mid-evening. But they'll be much closer to the Moon on Wednesday and Thursday nights.

This passage is just one of the rhythms of the night sky. The Moon and planets wheel through the background of stars in predictable fashion, while the stars themselves rise and set with clockwork precision.

The Moon, for example, wheels through the stars every four weeks. Saturn does it every 30 years, with a sort of stop-and-start motion. Right now, for example, Saturn appears to be moving westward through the stars -- toward Regulus. It'll keep up that motion for a few months, then reverse course and head eastward again. It'll return to its current position in the sky in about six months.

Saturn actually moves steadily forward in its orbit all the time, but our perspective on the planet changes as we orbit the Sun. So the orbital motions of the two planets combine to make Saturn appear to swing back and forth like the pendulum on a clock. It's a celestial mechanism that just keeps on tickin' -- maintaining the rhythms of the night sky.

Look for Saturn and Regulus below the Moon beginning around 9 o'clock tonight. Regulus is closer to the Moon right now, but Saturn is a little brighter, and it shows a bit of a golden color. We'll have more about this lineup tomorrow.

Script by Damond Benningfield, Copyright 2007

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