Supermoons are a rare type of full moon. They appear up to 14% bigger and 30% brighter than normal. While the full moon rises about once per month, supermoons can only occur a few times per year — max.
That's because the timing has to be just right. The Moon takes about 27.32 days to orbit Earth. During its orbit, the moon passes through two points: Perigee and apogee. Perigee is about 30,000 miles closer to Earth than apogee.
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