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Solar eclipse coming Sunday
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May 16, 2012 |
Something strange is about to happen to
the shadows beneath your feet.
On Sunday, May 20, the Moon will pass in front
of the sun, transforming sunbeams across the
Pacific side of Earth into fat crescents and
thin rings of light.
It's an annular solar eclipse, in which the Moon
will cover as much as 94% of the sun. Hundreds
of millions of people will be able to witness
the event.
The eclipse zone stretches from southeast Asia
across the Pacific Ocean to western parts of
North America, including, if the weather
cooperates, North Idaho.
In the United States, the eclipse begins around
5:30 p.m. PDT. For the next two hours, a
moon-shaped portion of the sun will go into
hiding. Greatest coverage occurs around 6:30 pm
PDT.
Because some of the sun is always exposed during
the eclipse, ambient daylight won't seem much
different than usual. Instead, the event will
reveal itself in the shadows. Look on the ground
beneath leafy trees for crescent-shaped sunbeams
and rings of light.
Near the center-line of the eclipse, observers
will experience something special: the "ring of
fire." As the moon crosses the sun dead-center,
a circular strip, or annulus, of sunlight will
completely surround the dark lunar disk.
Visually, the sun has a big black hole in the
middle.
The "path of annularity" where this occurs is
only about 200 miles wide, but it stretches
almost halfway around the world, passing many
population centers en route: Tokyo, Japan;
Medford, Oregon; Chico, California; Reno,
Nevada; Albuquerque, New Mexico, and Lubbock,
Texas. In those locations the ring of fire
phenomenon will be visible for as much as four
and a half minutes.
Do not attempt to look at it directly, however.
"The ring of sunlight during annularity is
blindingly bright," cautions NASA's leading
eclipse expert Fred Espenak of the Goddard Space
Flight Center. "Even though most of the Sun's
disk will be covered, you still need to use a
solar filter or some type of projection
technique. A #14 welder's glass is a good
choice. There are also many
commercially-available solar filters."
Many astronomy clubs will have solar-filtered
telescopes set up for public viewing.
Through the eyepiece of such an instrument, you
can see the mountainous lunar limb gliding by
dark sunspots and fiery prominences. It's a
beautiful sight.
Be absolutely sure, however, that any telescope
you look through is properly filtered. Magnified
sunlight can cause serious eye damage even
during an eclipse.
A safe and fun way to observe the eclipse is to
use your own body as a solar projector. For
example, try criss-crossing your fingers
waffle-style. Rays of light beaming through the
gaps will have the same shape as the eclipsed
sun.
Or just stand under that tree. The sight of a
thousand ring-shaped sunbeams swaying back and
forth on a grassy lawn or sidewalk is
unforgettable. |
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