The Super Moon

Perigee Moon March 2011 5

Perigee Moon March 2011 1

Perigee Moon March 2011 2

On March 16th NASA published in their science blog a “mark your calendar” note, and well, we did! Did you see the moon last night? It was brighter, very bright, and it looked incredible from the New York Manhattan sky. The lunar orbit brought it the closest its been to earth for 20 years. Cool right?

“The last full Moon so big and close to Earth occurred in March of 1993,” says Geoff Chester of the US Naval Observatory in Washington DC. “I’d say it’s worth a look.”

Full Moons vary in size because of the oval shape of the Moon’s orbit. It is an ellipse with one side (perigee) about 50,000 km closer to Earth than the other (apogee): diagram. Nearby perigee moons are about 14% bigger and 30% brighter than lesser moons that occur on the apogee side of the Moon’s orbit.

A perigee full Moon brings with it extra-high “perigean tides,” but this is nothing to worry about, according to NOAA. In most places, lunar gravity at perigee pulls tide waters only a few centimeters (an inch or so) higher than usual. Local geography can amplify the effect to about 15 centimeters (six inches)–not exactly a great flood.

The Moon looks extra-big when it is beaming through foreground objects–a.k.a. “the Moon illusion.”
Indeed, contrary to some reports circulating the Internet, perigee Moons do not trigger natural disasters. The “super moon” of March 1983, for instance, passed without incident. And an almost-super Moon in Dec. 2008 also proved harmless.

The super perigee moon as seen from London. Scientists said Saturday night’s moon appeared 14 percent larger and 30 percent brighter than normal as its lunar orbit brought it the closest its been to earth for 20 years.