The eclipsed moon, illustrated for Dec. 31, 2009, rides high above the Cathedral of Santa Maria del Fiore in Florence, Italy.
Credit: Starry Night Software
Eclipses of the moon occur twice a year, on average. Each eclipse is visible only on the half of the Earth turned towards the moon at the time the Earth's shadow falls on the moon.
There will be a partial eclipse of the moon on New Year's Eve, Dec. 31. Because of its timing, it will not be visible in North and South America, but will be visible over most of Europe, Africa, and Asia.
The event will also mark the second full moon of the month in North America, thereby garnering the title of "blue moon." Unless unusual atmospheric circumstances come into play ? such as widespread dust from a volcano ? the moon will not be blue, however.
Since it is a partial eclipse, the moon will just brush past the darkest part of the Earth's shadow, never becoming totally immersed. It will, however, be deep enough into the shadow that shading and reddish color should be visible.
Even though the eclipse isn't visible for most of us in North America, it's still possible to enjoy this event through astronomy simulation software like Starry Night. An armchair skywatcher can use this software to view the eclipse from any point on Earth.
Here's how the eclipse will play out (these times will be the same for most of western Europe and central Africa):
As the sun sets in the southwest, the full moon rises in the northeast. At 6:17 p.m. local time Friday the moon begins to enter the Earth's shadow, though it is undetectable at first. At? 7:52, the moon enters the darkest part of the Earth's shadow, called the umbra. Maximum eclipse is at 8:23, and the moon leaves the umbra at 8:53. The last traces of the shadow are gone by 10:28.
Observers in other parts of the Old World will have to make adjustments for their local time zones. Australians may catch a glimpse of the eclipse just before moonset at dawn on Jan. 1. Again, the eclipse is not visible from the Americas.
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