Scientists Predict 60 billion Habitable Planets in Milky Way Galaxy

The Milky Way galaxy alone could contain 60 billion planets orbiting red dwarf stars in its habitable zone, a new study conducted by the University of Chicago and Northwestern University.

Red dwarfs are common type of stars in the Milky Way galaxy. They are smaller and fainter with low radiance than other stars like the sun.

Earlier, based on data collected from NASA's Kepler spacecraft, scientists had predicted that there could be one Earth-size planet in the habitable zone of each red dwarf.

They have now doubled the number of life-sustaining planets after discovering how cloud cover helped an alien planet support life. Cloud covers control the temperature of the planet thus supporting life.

The habitable zone is a space around a star where orbiting planets with ample atmospheric pressure can maintain liquid water at their surface. The method for estimating the zone was the same for decades. However, earlier the cloud cover factor was ignored while rendering the habitable zone. It has now been deemed a crucial dynamic as it is a major temperature controlling factor.

Researchers conducted computer simulations of cloud behavior on alien planets. The findings expanded the habitable zone of red dwarfs.

Scientists said that planets believed to support life are present in the habitable zones and they are estimated to receive the right temperature to have liquid water on their surfaces which makes clouds.

"Clouds cause warming and they cause cooling on Earth. 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," said Dorian Abbot, assistant professor in geophysical sciences at the University of Chicago, said.

They also suggest that astronomers exploring planets orbiting red dwarfs could look for cloud covers as an evidence of life.

'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.' Nicolas Cowan, another author of the study and a postdoctoral fellow at Northwestern University, said.