When the Moon passes between the Sun and the Earth, the event is solar eclipse. The Sun is either fully or partially covered. A total solar eclipse occurs when the Sun is completely or totally covered 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. The total solar eclipse is going to take place on 22nd July 2009. The longest total solar eclipse of the century and the next solar eclipse of this kind is estimated to occur in the next century on 13th June 2132.

During this eclipse of the Sun is visible from within a narrow corridor that traverses half of Earth. The eclipse (the moon’s penumbra) starts in West India touches the shore in Surat, heads towards Butan touching the southern tip of Nepal and Northern edge of Bangladesh. It crosses Himalayan Mountains and passes over the central China touching the cities Chengdu, Suining, Chonging, Wuhan, Xiaogan, Hangzhou, and Shanghai. It continues its path into the Pacific Ocean encountering islands such as Toshima and Akusaki south of Japan and ends at Marshall Islands. The path of totality will cover approximately 9,500 miles or 15,200 Km.

How the Moon covers the Sun?
It is known that the Moon is smaller than the Sun in size then how is that we observe the Moon covering the Sun totally on total solar eclipse? The reason is their apparent sizes. The match between the apparent sizes of the Sun and Moon during a total eclipse is a coincidence. The Sun’s distance from the Earth is about 400 times the Moon’s distance, and the Sun’s diameter is about 400 times the Moon’s diameter. Because these ratios are approximately the same, the sizes of the Sun and the Moon as seen from Earth appear to be approximately the same! Is it not the wonderful creation of the Creator of Universe?!

What is the magnitude of an eclipse?
The Moon’s orbit around the Earth is an ellipse, as is the Earth’s orbit around the Sun; the apparent sizes of the Sun and Moon therefore vary. The magnitude of an eclipse is defined as the ratio of the apparent size of the Moon to the apparent size of the Sun during an eclipse.

An eclipse when the Moon is near its closest distance from the Earth, i.e. near its perigee, can be a total eclipse because the Moon will appear to be large enough to cover completely the Sun’s bright disk, or photosphere. A total eclipse has a magnitude greater than one.

Conversely, an eclipse when the Moon is near its farthest distance from the Earth, i.e., near its apogee, can only be an annular eclipse because the Moon will appear to be slightly smaller than the Sun. The magnitude of an annular eclipse is less than one.