On December 31, the Moon will undergo a partial lunar eclipse. This eclipse is considered "partial" because Earth's umbral shadow — the shadow's darkest part — will cover only 8 percent of the Moon at maximum. But the entire face of the Moon will pass through the lighter penumbra and turn a light gray.

A lunar eclipse occurs when the Sun, Earth, and Full Moon align in that order. Viewers can expect to see a bite taken out of the Full Moon's southern limb, while the rest of the disk takes on a more grayish hue than normal.

Residents of Europe, Asia, Africa, and Australia will get the best views. In North America, those in the far northeast will see the end of the eclipse, and those in the far northwest will see the eclipse begin.

The eclipse will begin at 17h17m Universal Time (12:17 p.m. EST). It will take 4 hours and 11 minutes for the Moon to pass through Earth's shadow completely. Maximum will occur at 19h23m UT (2:23 p.m. EST, 10:23 a.m. AKST).

The next partial lunar eclipse will occur June 26, 2010, and the next total lunar eclipse will be December 21, 2010.