Monday, August 27, 2007

[FOTHP] Lunar Eclipse Aug 28th

Friends of the Hudnall Planetarium,

Total Lunar Eclipse, August 28, 2007
In the early morning hours of Tuesday, August 28, 2007, the Moon will undergo a total lunar eclipse. A lunar eclipse occurs whenever the Sun, Earth, and Moon line up with the Earth in the middle. Under such an alignment, the Sun's light is blocked by the Earth, casting a shadow across the Moon's face, turning it a dramatic blood-red shade.
If the weather cooperates, you should be able to see the eclipse beginning at 3:51 am. The eclipse will last about three and one-half hours, ending at 7:24 am. Mid-eclipse, when the moon is the darkest, will occur at 5:37 am. The moon will be high in the southwestern sky at the beginning of the eclipse and will sink closer to the western horizon as the eclipse progresses. The moon will actually set at about 7:00 am, which is before the last part of the eclipse is over.
Lunar eclipses occur only during Full Moon and when the Moon passes through some portion of the Earth's shadow. The Earth's shadow is composed of two parts -- the umbra and the penumbra. The two parts of the Earth's shadow form long cones pointed away from the Earth, and are nested inside one another. The outer shadow is the penumbral cone, where the Earth blocks only part of the Sun's light. The inner shadow is the umbral cone, and is the darkest region where the Earth blocks all the Sun's light. When the Moon is completely inside the inner umbral cone, totality will occur. During this time, the Moon will not be completely black but may appear a deep red color. The reddish color comes from sunlight that is bent around the Earth by the refractive properties of the atmosphere. In a sense, the Earth's atmosphere behaves like a big lens, bending some of the Sun's light around the planet. Red light is refracted more than other colors of sunlight, so the red light strikes the Moon, creating the blood-red Moon.
The Moon is still in the penumbral shadow of the Earth about an hour before and an hour after totality. But the penumbral part of the Earth's shadow is faint and you will not notice the Moon being darkened unless you observe it with sensitive light measuring equipment.
If the weather does not cooperate or if you just can't force yourself to get up early on Tuesday morning, your next opportunity to see a total lunar eclipse will be February 21, 2008. Get out and enjoy your universe!

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