Day 3 - Penumbra = secondary shadow Only park of the sun is...

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Lunar phases and Eclipses What did ancient people know about the sky? (Archeoastronomy) The Moon’s appearance changes. It goes through phases. WHY? Look carefully at the portion of the Moon that is illuminated. Have any features changed in regions that are bright? Not much! We always see a portion of the “man in the moon” face. Synchronous rotation Orbital period = revolutional period One rotation = one revolution (about 27 1/3 days) – the rotational period is a little bit less the phase cycle. Phase cycle is about 29 ½ days due to the Earth’s motion around the sun. Umbra = darkest part of shadow Sun completely blocked (so at X – a total eclipse is observed).
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Unformatted text preview: Penumbra = secondary shadow Only park of the sun is blocked (so at Y a partial eclipse is observed). When the umbra doesnt reach the Earth, the Moon doesnt completely hide the Sun. At A, you see bulls eye effect. This is called an Annular eclipse (a kind of solar eclipse). Solar corona (outer atmosphere of the sun) is visible during totality. Refraction by Earths atmosphere allows us to see Moon in umbra Refraction when light bends as it encounters and move through a different medium. Dust scatters blue light creating reddish appearance of eclipsed moon....
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This document was uploaded on 01/26/2011.

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