Way..... Out there !

Way..... Out there !
Deepest, most colorful Hubble image yet of our universe. Click for info.

Sunday, February 17, 2008

Lunar Eclipse Wednesday

If the weather permits – and that's a big if – a total eclipse of the moon will be nearly impossible to miss here Wednesday evening. Conveniently arranged to appear in full color at prime viewing time, this will be the last such eclipse for nearly three years. The next total lunar eclipse visible anywhere isn't due until December 20-21, 2010. 

For a front-row seat, just go outside at about 8:43 pm and look up. The moon should be high in the sky overhead and just starting to enter Earth's outer shadow (the penumbra). At 10 pm the 52-minute period of total eclipse will begin as the moon slides into the inner shadow (the umbra). By 12:09 am Thursday, the whole thing will be over. 

During the event, the Moon makes a broad triangle with the bright planet Saturn and the somewhat fainter star Regulus, which marks the heart of Leo, the Lion.

This is the last of three total lunar eclipses within a year's time. The previous event, last August 28th, favored the Far West. The one before that, on March 3, 2007, favored eastern North America and Europe.

How and Why

A total lunar eclipse occurs when the Sun, Earth, and Moon form a nearly straight line in space, so that the full Moon passes through Earth's shadow. Unlike a solar eclipse, which requires special equipment to observe safely, you can watch a lunar eclipse with your unaided eyes. Binoculars or a telescope will enhance the view dramatically.

The outer part of Earth's shadow, the penumbra, creates only a slight dusky shading on the lunar disk. But as the Moon begins to move into the central and darkest part of Earth's shadow, the umbra, there's an obvious and ever-larger "bite" in the full Moon. The partial eclipse is then under way.

The total eclipse begins when the Moon is fully within the umbra. On February 20th, totality lasts 52 minutes. But the Moon likely won't disappear completely. It usually glows as an eerie, coppery red disk in the sky, as sunlight scattered around the edge of our atmosphere paints the lunar surface with a warm glow. This is light from all the sunrises and sunsets that are in progress around Earth at the time.

Visit Sky and Telescope magazine's website for much more on the eclipse and astronomy in general.

No comments: