The largest full moon of 2013, a so-called "supermoon," will light up the sky this weekend.
At 7 a.m. EST on June 23, the moon will arrive at perigee — the point in its orbit closest to Earth. The distance between the moon and Earth on Sunday will be 221,824 miles (356,991 kilometers). Now the moon typically reaches perigee once each month (and on some occasions twice), with their respective distances to Earth varying by 3%.
But Sunday's lunar perigee will be the closest the moon has come to Earth in 2013. And 32 minutes later, the moon will officially turn full. The close timing of the moon's perigee and its full phase are what will bring about the biggest full moon of the year, a celestial event popularly defined by some as a "supermoon."
You can watch a free webcast of the 2013 supermoon full moon on SPACE.com on Sunday at 9 p.m. EST, courtesy of the skywatching website Slooh Space Camera.
While the exact time of the full moon theoretically lasts for just an instant, that moment is imperceptible to casual observers. The moon will appear full a couple of days before, and after the actual full moon, most will claim seeing the nearly full moon as "full." Because the shaded strip is so narrow, and changing in apparent width so slowly, it is hard for the naked eye to tell in a casual glance whether it's present or on which side it is.
During Sunday's supermoon, the moon will appear about 12.2% larger than it will look on Jan. 16, 2014, when it will be farthest from the Earth during its apogee.
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