UNH Institute for the Study of Earth, Oceans, and Space

A Mid-Winter Treat: Sky-watchers will enjoy a total eclipse of the Moon this week

By Carmelle Druchniak
UNH News Bureau

Those hardy enough to brave the winter chill Thursday night will be rewarded with a celestial show that's hard to beat: a total lunar eclipse.

Thursday night, January 20, sky-watchers in North America will have front-row seats for the first total lunar eclipse in more than two years.

A total lunar eclipse occurs when the Sun, Earth, and Moon form a straight line in space and the Moon passes through the Earth's shadow. This can happen only on a night when the Moon is full, as it is Jan. 20. Unlike a solar eclipse, which requires special equipment to observe safely, a lunar eclipse can be viewed unaided. Binoculars or a small telescope can enhance the view.

According to the magazine Sky & Telescope: As the Moon moves into the Earth's outer shadow, or penumbra, it will begin to fade slightly, but the effect is almost imperceptible. Once the Moon encounters the dark inner shadow, or umbra, the fact that it is undergoing an eclipse will be obvious to anyone who looks up. The part of the Moon in the umbra should appear dark reddish-orange, while the part still in the penumbra might look straw colored. During totality, when the Moon is fully within the umbra, it will remain dimly visible as sunlight scattered by our atmosphere paints the lunar surface with a warm, reddish-orange glow. As the Moon emerges back into full sunlight, it will regain its former brilliance. From start to finish, the event takes about 4-1/2 hours.

Those in New Hampshire should head out the front door about 9:30 p.m. to catch the first visible shading of the lunar surface. Totality is expected around 11 p.m.

For additional comment, contact Joseph Hollweg, UNH professor of physics, of the UNH Institute for the Study of Earth, Oceans and Space, at 603-862-3869 or 603-868-2765. Or call Carmelle Druchniak, UNH News Bureau, 603-862-1462.

January 18, 2000

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