Monday, November 06, 2006

What's the black dot on the sun!

No need to worry on Wednesday if you look through a solar telescope and see a black dot on the face of the sun -- it is just the planet Mercury. Every three to thirteen years, Mercury's orbit takes it directly in front of the sun as seen from the Earth. Mercury actually orbits the sun every 115 days as seen from the Earth, but most of the time it misses the sun as seen from Earth. When the geometry is right, however, we see a transit. The last such crossing was in May, 2003, and the next one will not be until May 2016!

DO NOT try and look at the transit unless you are using a telescope with a solar filter! Mercury is too small to see with your unaided eye, and looking at the sun with a telescope or binoculars without a filter will blind you! Also, don't use "eclipse glasses" -- cardboard eyeglasses with Mylar filters -- to look through a telescope, because these glasses were only designed to look at solar eclipses with the naked eye. The extra light collected by a telescope could burn right through those glasses!

Your best bet is to find a local astronomy group that may have a solar telescope set up in your neighborhood. If there are any sunspots visible (not many are around right now), you can notice that sunspots are actually brown when compared with the pitch black of Mercury's night side.

If you live in Europe, Africa, or the Middle East, I'm sorry, but you are out of luck. The sun sets before the transit begins and rises after the transit ends. For much of the rest of the world, you can see the transit. This website will tell you what time of day you can see it. The transit lasts 5 hours, so you have plenty of time to wait for the hole in the clouds or to get out of school.

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