Celestial Event: Mercury to pass face of the sun

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And we'll miss it

A rare passage of Mercury in front of the Sun as seen from Earth will take place on Wednesday, 8 November. The last time such a transit of Mercury occurred was in 2003 and it will not reoccur until 2016.
Mercury will appear as a tiny black circle just 1/200th the width of the Sun. It will take almost five hours for Mercury's orbital motion to carry it completely across the Sun from Earth's point of view.
In order for transits to occur, Mercury has to come exactly between Earth and the Sun. If Mercury and Earth orbited the Sun in the same plane, this would happen every 116 days – when Mercury, which orbits the Sun every 88 days, catches up to Earth in its orbit.
But Mercury usually passes just above or below the Sun from our point of view because its orbit is tilted by 7° with respect to that of the Earth. The tilt means that Mercury spends most of its time above or below the Earth's orbital plane, and that the two planets only share the same plane at two points in their orbits – along the line where the two planes intersect.
A transit can happen only when Mercury is crossing Earth's orbital plane at the same time that it catches up to Earth in its orbit around the Sun. This happens about 13 times per century.
Like Mercury, Venus orbits closer to the Sun than Earth does, and it also has transits. But its longer orbital period makes Venus's transits even rarer, with only two occurring this century. One was in 2004 and the other will take place in 2012.

Widely visible

Mercury's transit on 8 November will be visible from a broad swath of Earth that includes the Americas, Australia and eastern Asia.
It will not be visible in Europe, Africa or the Middle East.
Mercury will start moving across the Sun's face at 1912 GMT (1412 EST). For observers in the Americas, the Sun will set before Mercury finishes its transit, except for those on the west coast of North America.
For observers in eastern Asia and most of Australia, the transit will already be underway by the time the Sun rises. Mercury will leave the Sun's face at 0010 GMT on Friday (1610 PST on Thursday).
Observing the transit will require a telescope or binoculars and special precautions – looking directly at the Sun can cause permanent vision damage.
You can safely observe the Sun through a telescope or binoculars if it is fitted with a specially designed solar filter. If you do not have a solar filter, you can project the image onto a piece of white, flat material like cardboard. Even then, you should take breaks to avoid overheating and damaging the optics.

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