60 Billion Planets In Milky Way Are Habitable For Alien Life, Study Says
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The 60 billion planets that are believed to be in the "habitable zone" -- planets close enough to their stars to possibly support water, and thus life -- number twice as many habitable planets as were previously thought to exist.
According to the study, the reason researchers think there are twice as many habitable planets as before has to do with cloud coverage, something the researchers say hasn't been given enough study.
Planets around red dwarf stars have to be close to them in order for their water to not freeze, because the stars are not nearly as warm as, for instance, Earth's sun. But if planets are too close to their red dwarf stars their water vaporizes. If they are too far, water freezes. The researchers say that planets that have previously been thought to be too close to their red dwarf star -- and thus within the water-evaporating zone -- may actually be able to support water because of cloud coverage.
Using 3D computer simulations to look at how air and moisture moves along a planet close to its red dwarf, the researchers determined that clouds would reflect light back at the red dwarf and keep the planet from getting too hot for water.
"Clouds cause warming, and they cause cooling on Earth," said Dorian Abbot, an assistant professor at the University of Chicago and a co-author of the study. "They reflect sunlight to cool things off, and they absorb infrared radiation from the surface to make a greenhouse effect. That's part of what keeps the planet warm enough to sustain life."
The researchers say they may be able to eventually confirm their computer simulated findings when the James Webb Space Telescope, an infrared-optimized space telescope, launches in 2018.
"If you look at Brazil or Indonesia with an infrared telescope from space, it can look cold, and that's because you're seeing the cloud deck," said Nicolas Cowan, a postdoctoral fellow at Northwestern's Center for Interdisciplinary Exploration and Research in Astrophysics and one of the study co-authors. "The cloud deck is at high altitude, and it's extremely cold up there."
According to Abbot, observations like that from the James Webb Telescope could be "confirmation that you do have surface liquid water."
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