Mercury Transit
A rare astronomical alignment takes place tomorrow, as the planet Mercury passes across the face of the Sun -- an event known as a transit. It's not visible to the unaided eye because Mercury's so small. But several web sites will provide views of the event from the ground or space.
The alignment between Earth, Mercury, and the Sun is such that transits occur just 13 times every century. Right now, they occur only within a few days of May 8th or November 10th.
In centuries past, astronomers used transits of Mercury and Venus to try to figure out the scale of the solar system. They also measured the sizes of the two planets, and looked for signs of atmospheres.
Today, the transits aren't that useful scientifically -- at least not in our own solar system. But transits in other solar systems are helping astronomers discover planets that orbit other stars. A space mission called Kepler is expected to discover hundreds of planets, and reveal important details about many of them -- like their suitability for life. More about the Kepler mission tomorrow.
The Mercury transit begins at 1:12 p.m. Central Standard Time tomorrow, when the planet first touches the solar disk. It ends about five hours later.
Don't try to look at it yourself, though. It's dangerous to look at the Sun, and you can't see Mercury anyway. Your best bet is to find a web site with images of the event. We'll provide some links on our own website -- stardate.org .
Script by Damond Benningfield, Copyright 2006
For more about the Kepler Mission, visit NASA's website at http://kepler.nasa.gov.
For more skywatching tips, astronomy news, and much more, read StarDate magazine.
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