Henry writes “A layman’s guide to the July 2010 Total Solar Eclipse”

Dr Henry Woodruff is a guide at Sydney Observatory and acting Curator of Astronomy

Image courtesy of Fred Espenak – NASA/Goddard Space Flight Center

On July 12 2010 the Moon will once again throw its shadow on the Earth, in an event astronomers like to call a solar eclipse. And since the Sun will be entirely hidden behind the Moon, we call it a total solar eclipse (as opposed to a partial solar eclipse).

We live in astronomical goldilocks times, since the distance of the Moon from the Earth is juuuust right, so that the apparent size of the Moon is very close to that of the Sun, allowing for spectacular solar eclipses. This will not always hold true, since the Moon is slowly edging away from us at roughly 38 mm every year. Give it enough time and the Moon will appear smaller than the Sun in the sky, and will not be able to completely “cover it up”.

Unfortunately, the path of the Moon’s shadow will not pass any part of Australia this time. Instead, some of the South Pacific and a tiny bit of South America will witness this special event (see eclipse map above , courtesy of Fred Espenak – NASA/Goddard Space Flight Center).

The partial eclipse will begin at 3:09:41 on Monday morning, July 12 2010 (all times are AEST, i.e. Sydney time). The total eclipse begins over an hour later, at 4:15:15. The Sun, Moon and Earth will be “exactly” lined up at 5:34:38, and those lucky enough to view the total eclipse will regain view of the Sun’s edge at 6:51:42 and will be able to breathe freely again at 7:57:16, when the last bit of the Moon fully uncovers the Sun.

The next solar eclipse will not be visible from Sydney until July 22 2028. However, just to put those who believe the world will end in December 2012 on edge, there will be a total eclipse visible from Cairns and surrounds on November 14 2012. Perhaps some money can be made that day :)