Astronomers have discovered what they say is the most Earth-like planet yet detected - a distant world that is similar in size to Earth and exists in a zone that is not too hot or too cold for life to exist. The discovery was detailed in Friday's issue of the journal Science. The find, announced Thursday, excited planet hunters who have been searching the Milky Way galaxy for years for potentially habitable places outside our solar system. The planet was detected by the Kepler telescope, a National Aeronautics and Space Administration orbiting platform that examines the galaxy for subtle changes in brightness that indicate an orbiting planet is crossing in front of a star. From the changes, scientists can calculate a planet's size and make certain inferences about its composition. The newly found planet, called Kepler-186f, circles a red dwarf star 500 light years from Earth in the Cygnus constellation. A light year is nearly 10 trillion kilometers. The planet is about 10 percent bigger than Earth and may have liquid water- a key ingredient for life - on its surface, scientists said. The planet probably is colored by an orange-red glow from its star and is most likely cooler than Earth, with an average temperature slightly above freezing.
