60 Billion Planets: Alien Life Could Be on Some, Says Study

We are not alone – at least in the number of planets in the Milky Way galaxy that could support life, according to new study conducted by University of Chicago and Northwestern University researchers.

As many as 60 billion planets orbiting "red dwarf stars" could be in the habitable zone for alien life, according to Astrophysical Journal Letters research that appeared last week. The study calculates the influence of cloud behavior on planets orbiting the dwarf stars, according to a University of Chicago news release.

"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."

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Cowan said habitable zones refer to the space around a star where orbiting planets can maintain liquid water. That, which had not changed in decades, largely neglects clouds, which exert a major climatic influence, said the news release.

"Clouds cause warming, and they cause cooling on Earth," said University of Chicago’s Dorian Abbot, co-author of the study said. Abbot is an assistant professor in geophysical sciences. "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 Times of India reported that NASA's Kepler Mission, which searches the Milky Way for planets in or near habitable zones, has identified approximately one Earth-size planet in the habitable zone of each red dwarf in the Milky Way. The University of Chicago-Northwestern study roughly doubles that estimate, according to the Times.

Cowan said for a planet to qualify as habitable in its study, it would have to be orbiting a star like the sun and complete that orbit approximately once a year. He said the planet must also be far enough away from its sun to maintain water.

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"If you’re orbiting around a low-mass or dwarf star, you have to orbit about once a month, once every two months to receive the same amount of sunlight that we receive from the sun," Cowan said in the news release.

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