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Poseidon's SupermoonThe supermoon hangs heavy over the Temple of Poseidon on Cape Sounion, south of Athens, around twilight on Saturday evening.Due to the moon's egg-shaped orbit, our natural satellite is at perigee—its closest approach to Earth—about once a month. The term "supermoon" was coined in 1979 to describe a full moon that coincides with perigee. (Apogee, when the moon is farthest from us, also occurs on a roughly monthly schedule.)At its closest on Saturday, the moon was 221,801 miles (356,955 kilometers) from our planet—and just minutes away from of the official full moon phase, at 11:35 p.m. ET."As a consequence, this translates into it appearing as much as 16 percent bigger and 30 percent brighter than other full moons of 2012—not a huge amount, but definitely noticeable," said Geza Gyuk, an astronomer at the Adler Planetarium in Chicago.—With reporting by Andrew Fazekas

Photograph by Anthony Ayiomamitis, TWAN