Thursday 2 May 2013

Total eclipse of the Sun visible from Australia, Papua New Guinea and the Solomon Islands, 9 May 2013.

A total eclipse will be visible from parts of the Southern Hemisphere on 9-10 May 2013. The eclipse will be visible across parts of the Northern Territory and Queensland on 9 May, before moving across the southeastern tip of Papua New Guinea, the D'Entrecasteaux Islands group and the central part of the Solomon Islands, before crossing the international dateline and ending in 10 May over the Pacific Ocean.

The path of the 9-10 May 2013 Solar Eclipse. The total eclipse will be visible along the central dark grey path. A partial eclipse will be visible from the shaded areas; in the lighters area the full eclipse will not be visible as it will have started before dawn (west) or will continue after sunset (east). The red lines are the equator and the international dateline. HM Nautical Almanac Office.

Solar eclipses occur as a result of the Moon passing in front of the Sun as seen from Earth. The Sun and Moon appear roughly the same size from Earth, though this is coincidental, the Moon being considerably smaller and closer than the Sun. 

The relative positions of the Sun, Moon and Earth during a Solar eclipse. Starry Night.

The Moon orbits the Earth every 28 days, but does not cause a Solar eclipse every month. This is because the orbit of the Moon is inclined to the orbit of the Earth about the Sun. Thus when the Moon is in the same part of the sky as the Sun it is usually either above or below it from our perspective (though it is effectively invisible at these times, since the Moon only 'shines' with reflected light from the Sun), with eclipses only occurring at those points in the cycle where the two orbital plains intersect.

How the differing inclinations of the Earth and Moon's orbits prevent us having an eclipse every 28 days. Starry Skies.

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