18 April 2007

Lunar Motion

The Moon is our nearest celestial neighbor and is, from our vantage point, the fastest moving object in the sky. It circles around the Earth in 29 days and as it does presents its slowly-changing face to us at different times of night. The New Moon is the phase when the Moon is "nearest" the Sun. This takes place on Tuesday April 17th this month. Each successive day the Moon's visible area grows, at first a thin sliver and then an ever-growing disk of light.

As the Moon moves across the backdrop of stars each night, it follows a path in the sky shared by the planets and the 12 Zodiac constellations. Many of these constellations are quite bright and form beautiful patterns with the Moon as it passes by. The thin crescent Moon will be low on the horizon on Wednesday April 18th, and during the 24 hours until evening on Thursday April 19th the Moon will have moved a considerable distance across the sky, past the cluster of stars called The Pleiades, then onward just next to Venus (which itself is near the bright stars of Taurus the Bull).

Over the next week as the Moon's phase grows it will slide through Gemini (on April 22nd), next to Saturn (on April 24th) and then into Leo the Lion on the 25th with a close approach to the bright star Regulus. The Moon itself makes a wonderful object to view through binoculars or an inexpensive telescope. As the phase of the Moon changes each night, a telescope will reveal the changing pattern of shadows cast by the craters and mountains on the Moon. Take a minute to enjoy the view over the next two weeks as the Moon grows from New to Full.