Eclipse in Prime Time
Stargazers in the central United States are perfectly positioned to view a total lunar eclipse on Wednesday, February 20.
A lunar eclipse occurs when the full Moon passes through Earth’s shadow. The lunar surface takes on the color of the shadow, which is often reddish, but can vary from bright orange to flat black, depending on atmospheric conditions.
The last visible lunar eclipse took place less than six months ago, but that was an early-morning event here, and many would-be viewers no doubt slept through the show. It’s a different story this time: the Moon enters the darkest part of Earth’s shadow, the umbra, at 7:43 p.m. CST. (Beforehand the Moon is covered by the penumbra, but this outer shadow is light enough that the full Moon appears nearly normal within it.) The total eclipse begins at 9 p.m., lasts for 51 minutes, then begins to exit the umbra. The visible eclipse ends at 11:09 p.m. when the Moon is once again entirely outside the umbra. (See diagram below.)
The next lunar eclipse visible here takes place after midnight on December 21, 2010.
The Moon moves through the shadow west to east, so the left side of the Moon will darken first as it enters the umbra. (Diagram by Dan Glomski, J.M. McDonald Planetarium) The lunar eclipse of 28 August 2007. This was thought to be one of darker eclipses in the last several years. (Composite image by Dan Glomski, J.M. McDonald Planetarium)
About one-third of Earth’s surface sees a lunar eclipse in its entirety. Another third (in this case, eastern Asia, Australia/New Zealand, and the western Pacific) misses out, since the eclipse takes place during the day, when the full Moon is not visible. The remaining part of the world sees the Moon rise or set with the eclipse in progress. The February 20 eclipse is beautifully timed for observers in the central U.S.; here it begins not long after moonrise and ends well before midnight. (Diagram by Mark Hartman, University of Nebraska-Kearney.)
For providing this information, a special thank you goes out to:
Daniel Glomski, Director, J.M. McDonald Planetarium
Vice President, Platte Valley Astronomical Observers
Program Coordinator, Sachtleben Observatory of Hastings College