A supermoon occurs when the moon is at its perigee, or closet point to Earth, while it moves in an elliptical orbit around Earth. Being at its perigee, the moon can appear up to 30% larger than normal, particularity when the moon is on the horizon. The moon can also appear larger when it is viewed with trees, buildings and objects in the foreground -- this is also known as moon or "Ponzo" illusion. This is the illusion that occurs when the human brain judges the size of objects based on the background.
When the moon arrives at its perigee, it will be 222,611 miles away from Earth, which is roughly 30,000 miles closer than the moon will be at its furthermost point during 2014.
Saturday's full moon is known as the "Full Buck Moon" or the "Thunder Moon". The Full Buck Moon gets its name because bucks start to grow new antlers this time of year and the thunder moon because of the frequency of thunderstorms during the summer.
The next supermoon will occur on August 10th and will be the biggest of the year; the last one of 2014 will occur on September 9th.
Sky watchers will also be able to see Mars, Saturn and the star Spica in the southwest sky Friday evening.