This weekend's full Moon is a "supermoon," as much as 50,000 km closer to Earth than other full Moons of the year. Rising in the east at sunset, the swollen disk will look extremely beautiful... because it is going to be eclipsed. On Sunday evening, Sept. 27th, the supermoon will pass through the shadow of Earth, turning the lunar disk a cosmic shade of red. Click here to view an animation of the eclipse and to find out when to look:
What makes the eclipsed Moon turn red? A quick trip to the Moon provides the answer: Imagine yourself standing on a dusty lunar plain looking up at the sky. Overhead hangs Earth, nightside down, completely hiding the sun behind it. The eclipse is underway.
You might expect Earth seen in this way to be utterly dark, but it's not. The rim of the planet looks like it is on fire. As you scan your eye around Earth's circumference, you're seeing every sunrise and every sunset in the world, all of them, all at once. This incredible light beams into the heart of Earth's shadow, filling it with a coppery glow and transforming the Moon into a great red orb.
Red isn't the only color. Sharp-eyed observers might also spot some turquoise, shown here in a photo taken by Jens Hackman during an eclipse in March of 2007:
You might expect Earth seen in this way to be utterly dark, but it's not. The rim of the planet looks like it is on fire. As you scan your eye around Earth's circumference, you're seeing every sunrise and every sunset in the world, all of them, all at once. This incredible light beams into the heart of Earth's shadow, filling it with a coppery glow and transforming the Moon into a great red orb.
Red isn't the only color. Sharp-eyed observers might also spot some turquoise, shown here in a photo taken by Jens Hackman during an eclipse in March of 2007:
Its source is ozone. Atmospheric scientist Richard Keen of the University of Colorado explains: "During a lunar eclipse, most of the light illuminating the moon passes through the stratosphere where it is reddened by scattering. However, light passing through the upper stratosphere penetrates the ozone layer, which absorbs red light and actually makes the passing light ray bluer." This can be seen, he says, as a soft blue fringe around the red core of Earth's shadow.
To catch the turquoise on Sept. 27-28, he advises, "look during the first and last minutes of totality. The turquoise rim is best seen in binoculars or a small telescope."
www.spaceweather.com
To catch the turquoise on Sept. 27-28, he advises, "look during the first and last minutes of totality. The turquoise rim is best seen in binoculars or a small telescope."
www.spaceweather.com
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