Sunday, December 19, 2010

Out of this world! Astronomical adventures of December 21, 2010

A couple of events in the world of astronomy will line up on Tuesday for the first time in 372 years and won't happen again for another 84 years. Most people probably know of both, but may not have put two and two together yet to realize they happen on the same day. The most obvious is the occurrence of the winter solstice, or what we commonly call the first day of winter. The other is a total lunar eclipse, which will be visible to all North Americans given the right weather conditions.

Starting with the eclipse... a lunar eclipse occurs when the Earth lines up directly between the sun and the moon, causing the Earth's shadow to be thrown over the moon. A total lunar eclipse is when the entirety of the moon is within the Earth's shadow and is less common than a partial eclipse. The next total lunar eclipse visible in the United States is not for another 3+ year - April 15, 2014. When the eclipse occurs, the moon will turn grey, then an orangish-red color as the eclipse becomes total, before returning to it's normal state.

Graphic courtesy Mr. Eclipse. Click for larger image.

In order to view the eclipse, you'd have to get up in the middle of the night (early Tuesday morning). The partial phase begins at 12:33 am CST. The total eclipse lasts from 1:41 am-2:53 am, or a lengthy 72 minutes, with "mid-eclipse" occurring at 2:17 am. The eclipse will be complete by 4:01 am. The graphic above shows these times as well (subtract one hour to convert from Eastern Standard Time). The only problem with Memphis viewing conditions will be the weather. Unfortunately, as of this writing (Sunday afternoon), is forecasting overcast conditions with a chance of light rain during that time frame so we may have to settle for pictures or video from other parts of the country, or you can check out a cool animation and see what you might miss at You can also see a series of photos taken of a lunar eclipse several years ago by here. If weather conditions improve, we'll be sure to let you know!

The other event, the winter solstice (Wikipedia), is the point in time when the Earth's axis is most inclined away the sun, yielding the shortest day of the year for the Northern Hemisphere and the beginning of our winter. It is also the day when the apparent position of the sun is the lowest in the sky for those in the Northern Hemisphere. Areas around the south pole get light all day as the Earth rotates, while those areas at the north pole are in darkness all day. (So I guess Santa Claus will be finishing up his list with the assistance of gas lanterns or a cozy fireplace). The exact timing of the solstice this year is 5:38 pm CST.

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