Solar eclipse mostly for penguins

By Joe Rao

updated 3:30 p.m. ET Feb. 1, 2008

On Feb. 7 the sun will undergo an eclipse that few will see. It will be an annular eclipse, a "penny on nickel" effect in which the moon will be too small to completely cover the disk of the sun.

The result will be the sun mimicking a blazing ring of fire — hence the term "annular," derived from the Latin anularis which means "ring." It will certainly be an unusual and spectacular sight, but only a very few people (and perhaps some penguins) will see it.

The region of visibility, if you haven't already guessed, is Antarctica, the only continent in the world with no permanent or indigenous human inhabitants. Larger than the United States, this frozen land is populated by approximately 2,500 people during the summer and fewer than 1,000 in the winter.

Eclipse in a freezer
A solar eclipse is visible wherever the shadow of the moon strikes the Earth. Actually, there are two shadows, the outer shadow, called the penumbra, from where a partial eclipse can be seen, and the darker umbra or central shadow from where the moon completely blocks the sun and the grand spectacle of a total eclipse can be observed.

A popular nickname for Antarctica is "the freezer." And it is over that part of Antarctica known as Ellsworth Land that the central axis of the Earth's shadow will make its landfall at 3:20 UT on Feb. 7. But it's not the umbra that will pass over this frozen wasteland, for the moon is 238,200 miles away. As a consequence, the cone-shaped umbral shadow is shorter than that, so the tip of this dark shadow cone ends up falling about 9,400 miles short of touching the Earth's surface.

This negative-shadow or "antumbra" — from where the solar annulus or "ring of fire" effect may be seen — projects onto the Antarctic landscape somewhat in a shape resembling a stubby cigar, and measures roughly 360 miles along its longest axis. It quickly will sweep over the Ellsworth Mountain range, the highest in Antarctica. Here also is Vinson Massif, 16,066 feet, constituting the highest point on the continent. The antumbra arrives here at 3:24 UT.

At 3:30 UT, the antumbra makes its closest approach to the geographic South Pole, passing less than 800 miles away to the east. Curving away to the northwest, the antumbra then sweeps across Marie Byrd Land, a region of western Antarctica east of the Amundsen Sea. Discovered and claimed for the United States by Richard E. Byrd in 1929, he named it in honor of his wife. However, due to its remoteness, even by Antarctic standards, most of Marie Byrd Land has not been claimed by any sovereign nation, making it by far the largest single unclaimed territory on Earth.

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