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January
8, 2009: When last month's full Moon rose over Florida,
onlooker Raquel Stanton of Cocoa Beach realized that something
was up.
"The
Moon was stunningly gorgeous--and it looked bigger than usual!"
she says. "My whole family noticed and watched in awe."
Like
millions of others around the world, she had witnessed the
biggest full Moon of 2008--a "perigee Moon," 14%
wider and 30% brighter than lesser Moons she had seen before.
"I'll never forget it."
Alert:
It's about to happen again.
This
Saturday night, Jan. 10th, another perigee Moon is coming.
It's the biggest full Moon of 2009, almost identical to the
one that impressed onlookers in Dec. 2008.
Above:
The perigee full Moon of Dec. 2008. "The moon was very
bright and BIG! Just watching it with my telescope was exciting
enough, but I had to take this picture for the records,"
says photographer Ron Hodges of Midland, Texas.
Johannes
Kepler explained the phenomenon 400 years ago. The Moon's
orbit around Earth is not a circle; it is an ellipse, with
one side 50,000 km closer to Earth than the other. Astronomers
call the point of closest approach "perigee,"
and that is where the Moon will be this weekend.
Perigee
full Moons come along once or twice a year. 2008 ended with
one and now 2009 is beginning with another. It's the best
kind of déjà vu for people who love the magic of a moonlit
landscape.
January
is a snowy month in the northern hemisphere, and the combination
of snow + perigee moonlight is simply amazing. When the Moon
soars overhead at midnight, the white terrain springs to life
with a reflected glow that banishes night, yet is not the
same as day. You can read a newspaper, ride a bike, write
a letter, and at the same time count the stars overhead. It
is an otherworldly experience that really must be sampled
first hand.
Above:
The perigee full of Dec. 2008. "A cold wind was blowing
as the Moon set over a neighbor's farm," says photographer
Eric Ingmundson of Sparta, Wisconsin. "Next time (Jan.
10th) I plan to use a tripod."
Another
magic moment happens when the perigee Moon is near the horizon.
That is when illusion mixes with reality to produce a truly
stunning view. For reasons not fully understood by astronomers
or psychologists, low-hanging Moons look unnaturally large
when they beam through trees, buildings and other foreground
objects. This weekend, why not let the "Moon illusion"
amplify a full Moon that's extra-big to begin with? The swollen
orb rising in the east at sunset may seem so nearby, you catch
yourself reaching out to touch it.
You
won't be the only one. Even at perigee, the Moon is 360,000
km away, yet the distant beauty beckons to poets, stargazers
and NASA with equal force: "Come back," it seems
to say, "I'm really not so far away."
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Author: Dr.
Tony Phillips | Credit: Science@NASA
more
information |
Perigean
tides:
A perigee 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.
Lunar
Perigee and Apogee Calculator
NASA's
Future: US
Space Exploration Policy |
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