Sky Show Friday: Biggest, Brightest Full Moon of 2008

By | December 12, 2008

Don’t expect to spot an Apollo lunar lander. But Friday night, 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 Friday’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.

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.

… “If you are charmed by the idea of seeing the biggest and brightest full moon visible in 15 years, be ready to go outside at sunset and watch for the rising moon in the east,” he said.

“Or stay up all night and watch as the moon rides through the overhead skies—either way it will be a beautiful sight.” – natgeo

One of my “end of the world dreams” involves the moon crashing into the Earth and school buses and toasters flying around due to low gravity as the moon gets close.

The size of the moon, or any object, depends on its distance. The “apogee” is the point in the orbit of the moon (or artificial satellite) where it is  most distant from the center of the earth, and thus, appears smallest. The percent change in aparant size depends on the change in the distance. In this case, (406479 -356566)/356566 x 100 = 13.998% So it will be 14% bigger than on  Nov 29, 2008 which was the last apogee. However, divide that number by 2 to get the amount bigger it will be over the average size during the last month; you get only 7%, which is not really noticible.

I think the photo above is a bit exaggerated… here is another:


The image above shows how strikingly different the Moon appears at a full-Moon perigee and apogee. Most people don’t notice the difference because they see the Moon in a sky that offers no reference by which angular extent may be judged. To observe the difference, you have to either make a scale to measure the Moon, or else photograph the Moon at perigee and apogee and compare the pictures, as I’ve done here.

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