Stargazing Special: Total Lunar Eclipse Coincides with Winter Solstice
Monday, December 20, 2010
If the skies are clear during the wee hours of Tuesday Dec. 21st, city dwellers will have a chance at glimpsing a rare site: a total lunar eclipse of a full moon. The moon will be high in the sky and easy to see thanks to the winter solstice, which coincidentally falls on Tuesday evening.
Usually the sun lights up the moon's surface. But at around 1:33 A.M. E.S.T. on Tuesday, the moon will begin to move into the earth’s shadow, at which point stargazers have some three and a half hours to witness the gradual darkening of the moon’s surface. From 2:41 to 3:53 A.M, the moon will be completely immersed in the earth's shadow. It's the first time in over 450 years that the lunar eclipse will occur on the same day as the winter solstice. A spectacular sky show like this won’t be visible until the next total lunar eclipse on April 15, 2014, according to the National Aeronautics and Space Administration (NASA).
Joe Rao, a lecturer at the American Museum of Natural History's Hayden Planetarium, says during the total lunar eclipse, the moon will take on a copper or ruddy hue (see the time-lapse video at right.) “This is due to the earth’s atmosphere refracting the rays of the sun into the earth’s shadow,” he explains. “And although no direct sunlight is hitting the surface of the moon, we’ll be able to see this weird color effect while the eclipse is total.” The very last bit of shadow will be gone by 5:01 A.M.
After the eclipse, the sun will rise around 7 A.M. and set at 4:30 P.M., making Tuesday Dec. 21st the shortest day (and longest night) of the year. At 6:38 P.M., when the sun’s rays reach the farthest point south of the equator, the winter solstice takes place. If you were standing at the Tropic of Capricorn at 23.5 degrees south latitude at noon on Tuesday, the sun would be directly overhead. ("Solstice" comes from the Latin meaning “sun standing still.”) But here in New York on Tuesday evening, the sun will appear low on the horizon. Then at 6:39 P.M., the sun begins its trajectory north.
Although the sun is moving closer north, Dec. 21st marks the beginning of cold winter days. The Hayden Planetarium's Joe Rao says there's an atmospheric lag and that's why we don't feel the warmth of the sun after the solstice. “It takes time for the atmosphere to react to the fact that the length of the time that the sun is in the sky has reached a minimum,” he says.
If you're not up to braving the cold early Tuesday morning, you can Web cast the total lunar eclipse at NASA's site. (Image left courtesy of NASA.) Or celebrate the winter solstice early at the Hayden Planetarium on Monday, Dec. 20th from 6:30 to 8 P.M. The night will include a discussion of the changing pattern of the sun, a film of images of the wintertime sky—Orion, Taurus, the Pleiades star cluster—and some stargazing. Or, simply check out the video below of the Paul Winter Consort visiting WNYC Host John Schaefer in the Soundcheck studios. The song featured is "Sweet for Solstice."