Sky Show Dec. 12: Biggest, Brightest Full Moon of 2008

Andrew Fazekas
for National Geographic News
Updated December 12, 2008

Don't expect to spot an Apollo lunar lander. But on December 12, weather permitting, sky-watchers around the world will see the biggest and brightest full moon of 2008.

Although a full moon happens every month, the one that rises tomorrow will appear about 30 percent brighter and 14 percent larger than the other full moons seen so far this year.

That's because our cosmic neighbor will be much closer than usual. The moon will be at its closest perigee—the nearest it gets to Earth during its egg-shaped orbit around our planet.

At its farthest from Earth, the moon is said to be at apogee. (Find out more about December 12's's perigee and watch a moon-facts video in National Geographic News's space blog, Breaking Orbit.)

Perigee and apogee each happen generally once a month, but the moon's wobbly orbit means that its exact distance at each of those events varies over the year.

The moon's phase can also be different during each apogee and perigee.

"Typically we don't have the full moon phase and perigee coinciding at the same time, so that makes this event particularly special," said Ed Krupp, director of the Griffith Observatory in Los Angeles, California.

What's more, tomorrow's event will be the closest lunar perigee since 1993, at 221,560 miles (356,566 kilometers) from Earth.

The moon's farthest apogee for the year will occur a couple weeks later on December 26, when the natural satellite will be 252,650 miles (406,601 kilometers) from Earth.

Highest Tide

Because this unusually close perigee is happening during a full moon, it is expected to have an effect on Earth's tides. (Get more moon facts.)

"While high tides happen each month when the sun, Earth, and the moon are aligned, there is going to be an enhanced effect, with the moon being the closest it's been in more than a decade," said Ben Burress, staff astronomer at the Chabot Space and Science Center in Oakland, California.

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