Study: More habitable planets may exist

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UNIVERSITY PARK, Pa., March 12 (UPI) -- The number of potentially habitable planets is greater than previously thought, a U.S. researcher says, and some are probably circling nearby stars.

Penn State post-doctoral geosciences researcher Ravi Kopparau says he has recalculated the frequency of Earth-sized planets in the habitable zones of low-mass stars, also known as cool stars or M-dwarfs.

"We now estimate that if we were to look at 10 of the nearest small stars we would find about four potentially habitable planets, give or take," Kopparapu said in a Penn State release Tuesday. "That is a conservative estimate. There could be more."

Scientists focus on M-dwarfs, he said, because the orbit of planets around M-dwarfs is very short, which allows scientists to gather data on a greater number of orbits in a shorter period of time than can be gathered on Sun-like stars.

M-dwarfs are also more common than stars like the Earth's sun, which means more of them can be observed, he said.

"The average distance to the nearest potentially habitable planet is about seven light years. That is about half the distance of previous estimates," Kopparapau said his analysis suggested. "There are about eight cool stars within 10 light-years, so conservatively, we should expect to find about three Earth-size planets in the habitable zones."

"This means Earth-sized planets are more common than we thought, and that is a good sign for detecting extraterrestrial life."