January 14, 2010

Best Annular Eclipse For 1,000 Years Closing In

Astronomers say that half the world will see the Sun become briefly reduced to a shinning ring surrounding a somber disk on Friday, when an annular eclipse runs from central Africa to eastern Asia.

This eclipse will be an estimated 185-mile band running 8,062 miles.  At one point it will set a duration record that is said to be unbeaten for more than a thousand years.

An annular eclipse is when the Moon passes directly in front of the Sun without completely blocking it, thus leaving a ring of sunlight glowing around the Moon.

The Moon's shadow, according to NASA's eclipse website, will strike the southwestern tip of Chad and western Central African Republic at 0514 GMT and will then fly across Uganda, Kenya, and Somalia.

NASA says that its path will then lead across the Indian Ocean, where the duration of "annularity" will be 11 minutes and eight seconds.  This will make it "the longest annular eclipse of the 3rd Millennium."

This record will not be beaten until December 23, 3043.

The lunar umbra, or shadow, will then cross Bangladesh, India, Myanmar and China before expiring in the Shandong peninsula at 0859 GMT.

People in eastern Europe, most of Africa, Asia and Indonesia, will be able to see a partial eclipse.

The next annular solar eclipse will not take place for another 29 months.

The Sky & Telescope magazine says that compared to other years, the number of eclipses in 2010 is meager although they provide an "interesting mix" for watchers.

Other than Friday's event, the only other cover-up of the Sun this year will take place on July 11, when a total eclipse will run across the Pacific, visible notably from Easter Island.

Total eclipses occur solely because of an unusual trick of celestial geometry.

The Sun is 400 times wider than the Moon, but is 400 times farther away.  It is because of this symmetry that the umbra is exactly wide enough to cover the face of the Sun.

However, the orbits of the Earth and Moon are not completely circular.  Tiny differences explain why some eclipses are complete and others show a thin ring of sunlight.

According to Sky & Telescope, there will be a total lunar eclipse this year on solstice day, December 21.


Image Caption: Annular solar eclipse on October 3, 2005. Courtesy Wikipedia


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