It will be a late event, languid. For people who live east of the Mississippi, the eclipse begins long after midnight. The lunar eclipse will last about three hours, with the moon falling into the depths of the Earth's shadow about an hour and twelve minutes at the height of the event.
As the Earth glides between the sun and the moon, changing the tone of the lunar surface from white to orange-red and back, you're seeing the effect of Earth's atmosphere is having on the color of sunlight passing through it. But the atmosphere is doing something else. Is in effect marked the sun's rays with the chemical fingerprints of the gases in the atmosphere.
In the past two years, two teams of astronomers have been using this effect to find out what the Earth would look like as a distant planet orbiting another star extrasolar. By analyzing the light reflected by the moon during a lunar eclipse - the light that has passed through Earth's atmosphere - gases that have been detected in the atmosphere that indicate the presence of organic life on the planet.
If steps baby equipment are any indication, the techniques being developed may be able to detect traces of organic life form in the atmosphere of an extrasolar planet - at least for rocky, Earth-mass planets orbiting relatively close stars sun - with large ground-based telescopes.
"It's an interesting experiment - one of the few I've seen that I would have thought of me," says Sara Seager, a physicist at the Massachusetts Institute of Technology studying exoplanets and their environments, and did not participate in any project.
"The Earth is our best laboratory, is the only planet we know of life," he says. "So I really want to understand what Earth would look like an exoplanet far."
Of particular interest are planets whose orbits bring them in front of their parent stars as seen from Earth - so-called transiting planets.
These are the types of extrasolar planets spacecraft and NASA's Kepler spacecraft CoRoT French Space Agency are currently hunting.
Kepler, in particular, is seeking more than 150,000 stars for Earth-mass planets in the habitable zones of their stars called. These are regions of space close enough to a star where liquid water could be stable on the surface of a planet orbiting at that distance.
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