By Megan Gannon
www.space.com7-1-13
Though only about dozen potentially habitable exoplanets have been detected so far, scientists say the universe should be teeming with alien worlds that could support life. The Milky Way alone may host 60 billion such planets around faint red dwarf stars, a new estimate suggests.
Based on data from NASAs planet-hunting Kepler spacecraft, scientists have predicted that there should be one Earth-size planet in the habitable zone of each red dwarf, the most common type of star. But a group of researchers has now doubled that estimate after considering how cloud cover might help an alien planet support life.
"Clouds cause warming, and they cause cooling on Earth," study researcher Dorian Abbot, an assistant professor in geophysical sciences at the University of Chicago, said in a statement. "They reflect sunlight to cool things off, and they absorb infrared radiation from the surface to make a greenhouse effect. Thats part of what keeps the planet warm enough to sustain life."
The habitable zone is defined as the region where a planet has the right temperature to keep liquid water on its surface, thought to be a requirement for life as we know it. If a planet is too far from its star, its water freezes; too close, water vaporizes. Since red dwarfs are dimmer and cooler than our sun, their habitable zone is much cozier than our solar systems....
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See Also:
Habitable Zone Redefined for Alien Planets - and Maybe Life SPACE NEWS
NASA Telescope Confirms Alien Planet in So-called Goldilocks Zone
New Earth-Like Planet Could Sustain Life, Scientists Claim
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