Solar Eclipse this Weekend

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http://science.nasa.gov/science-news/science-at-nasa/2012/15may_sunday/

Solar Eclipse this Weekend
NASA Science News

May 15, 2012: Something strange is about to happen to the shadows
beneath your feet.

On Sunday, May 20th, 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.^1

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: animated eclipse map
<http://shadowandsubstance.com/>.

In the United States, the eclipse begins around 5:30 pm 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 4
and a half minutes.

"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.

For more information about the solar eclipse, please view the
ScienceCast video Solar Eclipse over the USA
<http://www.youtube.com/watch?v=7YX2blo1eRk>.


Author:Dr. Tony Phillips
Production editor: Dr. Tony Phillips
Credit: Science@NASA

*More Information*


Footnote: (1) It's only when sunlight passes through a small aperture
that you the get the "pinhole effect" necessary for solar imaging. Gaps
in the leaves between trees or between interwoven human fingers are
perfect for this purpose.

Interactive Eclipse map
<http://eclipse.gsfc.nasa.gov/SEgoogle/SEgoogle2001/SE2012May20Agoogle.html>
-- from NASA

May 20th Annular Eclipse of the Sun
<http://www.skyandtelescope.com/observing/highlights/A-Preview-of-May-20ths-Annular-Eclipse-141037803.html>
-- Sky & Telescope

NASA's Solar Eclipse Home Page <http://eclipse.gsfc.nasa.gov/eclipse.html>

Details and Timetables
<http://eclipse.gsfc.nasa.gov/OH/OH2012.html#SE2012May20A> for the May
20th annular eclipse

Annular eclipse photo gallery
<http://spaceweather.com/eclipses/gallery_15jan10_page4.htm> -- from
spaceweather.com

Solar Eclipse over the USA <http://www.youtube.com/watch?v=7YX2blo1eRk>
-- ScienceCast video