Big Moonshine

[David Morris]

-----Original Message-----
From: NASA Science News [mailto:snglist at snglist.msfc.nasa.gov]
Sent: Tuesday, February 26, 2002 2:12 PM
To: NASA Science News
Subject: Big Moonshine

http://science.nasa.gov/headlines/y2002/26feb_bigmoonshine.htm?list649552

The Moon will become full on Feb. 27th. It happens every 29.5 days, yet this 
full Moon is special: It's the biggest and brightest of the year.

"Not all full Moons are alike," says astronomy professor George Lebo. 
"Sometimes pollution or volcanic ash shades them with interesting colors. 
Sometimes haloes form around them -- a result of ice crystals in the air."

"This full Moon is unique in another way," he says. "It will be closer to 
Earth than usual."

Right: The apparent size of the Moon at perigee (top) and apogee (bottom).

"The moon's orbit around our planet is not a perfect circle," Lebo explains. 
"It's an ellipse." At one end of the ellipse (called apogee) the Moon lies 
406,700 km from Earth. At the other end (called perigee) the Moon is only 
356,400 km away -- a difference of 50 thousand km!

When the Moon is full on Feb. 27th it will be near perigee -- close to 
Earth. As a result the Moon will appear 9% wider than normal and shine 20% 
brighter.

The extra moonlight is caused, in part, by the Moon's nearness to Earth. But 
that's not all. The Sun is closer to Earth, too. Lebo explains: "Every year 
during northern winter, Earth is about 1.6% closer to the Sun than normal. 
(Like the Moon's orbit around Earth, Earth's orbit around the Sun is 
elliptical. Our closest approach to the Sun is called perihelion.) The Moon 
reflects sunlight, so the Moon is brighter during that time."








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