Today there was an annular eclipse of the Sun. I was not in the path of visibility, but thanks to the Internet, I was able to watch via different viewing sites in China, Japan, California, New Mexico and Nevada.
An eclipse of the Sun happens when the Earth, Moon and Sun are in a straight line, with the Moon in the middle. If the orbit of the Moon was in a perfect circle and one the same plane as the orbit of the Earth and Sun, there would be an eclipse every month. But that is not the case. The Moon's orbit is a slightly different plane than that of the Earth's orbit around the Sun, so eclipses are unusual and worth getting excited about.
By far, the most interesting is the total eclipse of the Sun. That happens when the Moon is just the right distance from the Sun so that the disk of the Moon completely covers the disk of the Sun, making the Corona of the Sun visible.
Because of Kepler's First Law of Planetary Motion, the Moon orbits the Earth in an ellipse rather than a perfect circle. This means that sometimes the Moon is closer to the Earth during an eclipse so that it doesn't cover the Sun's disk completely. We call these "annular eclipses." Annular, not "annual" -- which comes from the word "annulus." This is a word that is sometimes used in math or geometry, but not often used in common English. It comes from the Latin "annulus" meaning "little ring."
When the solar eclipse occurs so that the Moon is too close to the Earth to completely cover the Sun's disk, what we see is a "little ring," or annulus of the Sun's disk.
Here are some pictures from Reno, Nevada, USA, that I snapped every ten minutes via USTREAM.com
8:20 PM Eastern Time
8:30 PM Eastern Time
8:40 PM Eastern Time
8:50 PM Eastern Time - and the clouds roll in!
9:00 PM Eastern Time - and the people on location are getting nervous with the cloud cover.
9:10 PM Eastern Time - the clouds are almost gone.
9:20 PM Eastern Time
9:29 PM Eastern Time - just at the crucial moment, clouds threaten!
The annulus is almost complete
A perfect ring of fire!
And now we begin to watch the reverse process.
This was a view via Slooh.com from Mt Fuji
USTREAM.com had several channels, one of which showed a multitude of Asian sites.