Distant solar systems eyed as home to life

A study of eight "solar twins" of our sun suggests any planets orbiting those stars may very well be hotter and more dynamic than Earth, U.S. researchers say. Scientists at Ohio State University, searching for alien life in a new way, studied stars that very closely match the sun in size, age, and overall composition to measure the amounts of radioactive elements they -- and their planets -- may contain. Elements such as thorium and uranium are essential to Earth's plate tectonics because they warm our planet's interior. Plate tectonics helps maintain water on the surface of the Earth, the researchers said, so the existence of plate tectonics is sometimes taken as an indicator of a planet's hospitality to life. Seven of the stars studied appear to contain much more thorium than our sun, which suggests any planets orbiting those stars probably contain more thorium, too, which means the interior of the planets are likely warmer than ours. That could allow plate tectonics to persist longer through a planet's history, giving more time for life to arise, the researchers said. "If it turns out that these planets are warmer than we previously thought, then we can effectively increase the size of the habitable zone around these stars by pushing the habitable zone farther from the host star, and consider more of those planets hospitable to microbial life," researcher Cayman Unterborn said.