Wednesday, July 22, 2009

The longest total solar eclipse

On 2009 July 22, a total eclipse of the Sun is visible from within a narrow corridor that traverses half the Earth. The path of the Moon's umbral shadow begins in India and crosses through Nepal, Bangladesh, Bhutan and China before curving south across the Pacific Ocean. A partial eclipse is seen within the much broader path of the Moon's penumbral shadow, which includes most of eastern Asia, Indonesia, and the Pacific Ocean.

A total solar eclipse is a spectacular natural phenomenon and many people travel to remote locations to observe one. In ancient times, and in some cultures today, solar eclipses have been attributed to supernatural causes. Total solar eclipses can be frightening for people who are unaware of their astronomical explanation, as the Sun seems to disappear in the middle of the day and the sky darkens in a matter of minutes.It occurs when the sun is completely obscured by the Moon. The intensely bright disk of the Sun is replaced by the dark silhouette of the Moon, and the much fainter corona is visible. During any one eclipse, totality is visible only from at most a narrow track on the surface of the Earth.

It is never safe to look at a partial or annular eclipse, or the partial phases of a total solar eclipse, without the proper equipment and techniques. Even when 99% of the Sun's surface is obscured during the partial phases of a solar eclipse, the remaining crescent Sun is still intense enough to cause a retinal burn, even though illumination levels are comparable to twilight.... Failure to use proper observing methods may result in permanent eye damage or severe visual loss.

Eclipse maps and data courtesy of Fred Espenak and Jay Anderson, "Total Solar Eclipse of 2009 July 22" (NASA/TP-2008-214169)

No comments: