March 2007

by Deane Morrison

March may not come in like a lion, but it certainly starts out in spectacular fashion. The fun begins around 6 p.m. on the 3rd, when the full moon rises in the midst of a lunar eclipse. At that moment, the moon will be just beginning to emerge from the Earth's umbra, or dark inner shadow. As the moon moves farther out of the umbra and through the penumbra, or light inner shadow, the lunar crescent starts fattening from east to west. Since that's opposite the direction the sun's light spreads over a young moon as it turns full, it'll be like watching the moon run through its waxing phases in reverse.

The Algonquin Indian tribes of the eastern United States and Canada called March's full moon the worm moon, for the softening of the ground and the reappearance of earthworm casts at this time of year. Other tribes called it the crow moon, for the cawing that heralds the end of winter; the crust moon, for the hard crust on snow that has melted and refrozen; or the sap moon, to welcome the start of maple sugaring season.

On the 20th, a thin crescent moon of the new cycle glows with two kinds of light below Venus. Venus, a brilliant beacon in the southwest, shines with reflected sunlight. But while the moon's bright crescent also reflects sunlight, the rest of its disk reflects the much fainter earthshine. Technically, earthshine is mostly reflected sunlight, too, but in this case it's sunbeams that have bounced off two bodies--Earth and the moon--before reaching our eyes.

The sun moves north most rapidly during March, the month when it's easiest to notice the lengthening of days. At 7:07 p.m. on the 20th, the sun crosses the equator into the northern sky. This, of course, is the vernal equinox, the start of spring in the Northern Hemisphere. The time of 7:07 p.m. is CDT because daylight saving time starts early this year--at 2 a.m. on the second Sunday of March, which is the 11th.

As skies darken, Saturn comes out between the bright star Regulus, in Leo, to the east and the lovely star cluster known as the Beehive to the west. Telescopic viewers will see

Saturn's rings quite tilted, and binocular viewers should not miss the chance to turn their lenses on the Beehive.

West of the Beehive, the knot of well-known winter constellations has a last hurrah in the evening sky. Sirius, the brightest star in the night sky, still shines low in the south. If you compare it to Venus and Saturn an hour or two after sunset, you'll see that Venus greatly out-dazzles the star, but Sirius more than holds its own against Saturn.

Jupiter, the only bright morning planet, beams above the sinuous form of Scorpius in the predawn sky. Mars and Mercury also appear in the morning, but too close to the sun for easy watching.

Speaking of easy, if you're looking for a book to explain the ins and outs of astronomy in clear language, try "Astronomy for the Utterly Confused," by University of Minnesota astronomy professor Terry Jones and Ingrid Johnson. If it's not in your local bookstore, you can order a copy by calling (612) 626-0559 or sending an e-mail to generalbooks@umn.edu.