The 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.
While a treat for sky-watchers, the supermoon (pictured behind Seattle's Space Needle this weekend) on Saturday wasn't a rare event: The full moon coincides with lunar perigee about once a year, on average. And because the size of the moon's orbit varies slightly, each monthly perigee is not always the same distance from Earth.
Seen from West Orange, New Jersey, the full moon hangs over the Manhattan skyline like a celestial clementine Sunday night.
In general, the moon appears redder near the horizon, because its light is passing through more of our planet's thick atmosphere than when the moon is higher—the atmosphere tends to scatter blue light, letting mostly red wavelengths through.
Shining through the clouds, the supermoon seems to hover above the statue of Christ the Redeemer in Rio de Janeiro, Brazil, in the wee hours of Sunday.
Far from a formal astronomical term, "supermoon" has also come to be used when perigee coincides with new moons—when the lunar orb positions itself between Earth and the sun, so that the side of the moon that faces us is unlighted.
"While we know that during new and full moons the tides are greatest—and if it's in concert with a storm surge, it might produce unusual flooding-there is no scientific evidence that earthquakes and other natural disasters are connected," Gyuk said.
Shining high over Austria Sunday night, the full moon paints the clouds with a halo of ethereal colors. Such lunar halos happen when moonlight interacts with the pencil-shaped ice crystals in high, wispy cirrus clouds.
The golden disk of a full moon rests over a Rio de Janeiro shantytown on Sunday.
No major effects on Earth have so far been linked to supermoons, the Adler Planetarium's Gyuk emphasized.
"Supermoons have been happening for billions of years, and nothing particularly special occurs on these dates—except, of course, for a beautiful full moon."
Photograph by Victor R. Caivano, AP
The Lotus Temple in New Delhi, India, seems poised to swallow the full moon in a picture taken Sunday night.
Next month the full moon will again roughly coincide with perigee, albeit one that puts the moon a bit farther away, at 222,750 miles (358,482 kilometers), Gyuk said.
So if you missed this weekend's sky show, don't worry, Gyuk said. June's "full moon will appear to be just half of one percent different in size" and "only one percent less bright" than May's supermoon.