There's Twice as Many Habitable Alien Planets Out There, Thanks to Clouds

There could potentially be more than double the number of habitable exoplanets orbiting red dwarf stars out there thanks to clouds, asserts a new study. If the assumption holds true, then there should be around 60 billion habitable planets in our Milky Way alone.

"Most of the planets in the Milky Way orbit red dwarfs," said Nicolas Cowan, a postdoctoral fellow at Northwestern University's Center for Interdisciplinary Exploration and Research in Astrophysics. "A thermostat that makes such planets more clement means we don't have to look as far to find a habitable planet."

Red dwarf stars are the most common type of star in the universe, and are smaller and fainter than our sun, which is brighter than 85 percent of the stars out there. A star's habitable zone is the area around the star where liquid water could potentially form on a planet, meaning that it isn't too close (hot) or too far (cold) from the host star.

The study, published in the journal Astrophysical Letters and conducted by researchers from the University of Chicago and Northwestern University, used computer models from 216 networked computers at the University of Chicago to simulate and analyze cloud behavior. Turns out that clouds have a greater impact on a planet's atmosphere than previously thought - enough to effectively double the size of the habitable zone around a red dwarf. Data from NASA's planet-hunting Kepler mission indicates that there is approximately one Earth-sized planet in every red dwarf's habitable zone. Now, astronomers can expect two.

"Clouds cause warming, and they cause cooling on Earth," said Dorian Abbot, a member of the team that conducted the research from the University of Chicago. "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."