Click the image to see the NASA article.
This month's full Moon is a "super Moon,” as much as 14% bigger and 30% brighter than other full Moons of 2012. This is because the Moon is at perigee tomorrow night when it's also full. Full Moons vary in size because the Moon's orbit is an ellipse, not a perfect circle, with one side about 50,000 km closer to Earth than the other (the apogee). Therefore, a full Moon during perigee is much brighter and appears extra-huge. Because of timing issues, very few full Moons happen at perigee, so this is a special treat.