According to a new study by researchers of the University of Chicago, the Milky Way alone hosts more than 60 billion alien planets that could support life but are hidden by clouds.

Previous data from NASA's planet-hunting Kepler spacecraft mission has led scientists to believe that there should be at least one Earth-size planet in the habitable zone of each red dwarf, the most common type of star. A study conducted on similar lines by researchers from the University of Chicago and Northwestern University found that this number could be doubled considering how cloud cover might help an alien planet support life.

Researchers analyzed the influence of cloud behavior on climate and how it doubles the number of potentially habitable planets orbiting red dwarfs, the most common type of stars in the universe. They concluded that the Milky Way alone could contain more than 60 billion alien planets that were capable of supporting life but have not been discovered due to cloud cover.

"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. That's part of what keeps the planet warm enough to sustain life."

A habitable zone is defined as a region where a planet has the right temperature to sustain water in its liquid form. If a planet is too close to its star, the water vaporizes and if it is too far, the water freezes. Since red dwarfs are cooler and dimmer than our Sun, scientists estimate that their habitable zone is much cozier than our solar system's.

"Most of the planets in the Milky Way orbit red dwarfs," said Nicolas Cowan, a postdoctoral fellow at Northwestern'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."

For the study, scientists used a 3-D climate model that was originally used to forecast global warming on Earth. With the help of this model, scientists were able to map out patterns on planets that orbit red dwarf stars. They discovered that huge, thick clouds develop over the part of the planet that faces its star. This in turn, reflects light and heat back to the star and keeps the planet from getting too warm.

The research was detailed June 27 in the journal Astrophysical Journal Letters.