NASA scientists believe that our galaxy contains 60 billion planets capable of supporting life.
Scientists previously predicted that there is one Earth-sized planet in the habitable zone of each red dwarf, the most common type of star. But now, a group of researchers believe that the estimate is double as cloud cover could help support alien life.
Planets with clouds may be cooler, as they are able to deflect heat from their star more easily. But the clouds also keep things on the planet warm enough to sustain life.
A study by the University of Chicago and Northwestern University estimated that the Milky Way has 60 billion planets that could support life.
The study also suggests other ways astronomers can test whether or not planets have cloud cover and water.
They estimated the number of habitable planets by using rigorous computer simulations of cloud behavior on planets. They found that cloud cover expanded the estimated habitable zone of red dwarfs.
"Clouds cause warming and they cause cooling on Earth," Dorian Abbot, assistant professor in geophysical sciences at the University of Chicago, said. "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."
Nicolas Cowan, author of the study, said, "If you're orbiting around a low mass or dwarf star, you have to orbit about once a month or once every two months to receive the same amount of sunlight that we receive from the sun."
Most of these habitable planets are tidally locked, meaning one side of the planet always faces the star.
Cowan said, "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. It's a confirmation that you do have surface liquid water."