May 4, 2012

On Saturday (May 5) at 11:35 p.m. EDT, the moon will officially turn full. And only 25 minutes later the moon will also arrive at perigee, its closest approach to Earth — a distance of 221,802 miles (356,955 kilometers) away.

The effect of this coincidence is a stunning skywatching sight called the “supermoon.”

In fact, this month’s perigee is the closest of any perigee in 2012 (they vary by about 3 percent, because the moon’s orbit is not perfectly circular). The result will be a 16 percent brighter-than-average full moon accompanied by unusually high and low tides this weekend and into the new week.