Lunar Escorts

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Like an aircraft carrier flanked by escort ships, the gibbous Moon is flanked by a couple of bright groups of stars and planets tonight. They curve high across the south at nightfall, to the west around midnight, and to the northwest as they set in the wee hours of the morning.

As you face south at nightfall this evening, look to the left of the Moon for the star Regulus and the planet Saturn. Saturn is the brighter of the two, and has a slightly golden color.

Then look about the same distance to the right of the Moon for the bright twin stars of Gemini -- Pollux and Castor. The planet Mars is to their west, and looks like an orange star. One way to pick out the two planets is that unlike the stars, they barely twinkle -- their light holds steady.

Regulus, Pollux, and Castor all lie quite close to the ecliptic, which is the Sun's path across the sky. So the Moon passes close to these stars every four weeks -- an interval known as the sidereal month.

The planets are close to the ecliptic, too, but it takes them longer to circle back to the same stars. Mars, for example, will return to Gemini in about a year and a half. But Saturn is much farther out in the solar system, so its motion against the starry background is much slower. It won't return to the same spot close to Regulus for almost three decades.

The Moon will stand much closer to Regulus and Saturn tomorrow night -- and we'll have more about that tomorrow.

Script by Damond Benningfield, Copyright 2008

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