The United States Aeronautic Space Agency (NASA’s) Kepler telescope has been busy in the hunt for alien life, finding over 4,000 new planets outside Earth’s solar system over the past three years. Now a team of astronomers has narrowed down this list to those with the most potential to have liquid water, or even life.They pinpointed 20 out of the 4,000 that are most likely to be like our own, and are starting to look more closely at these candidates. . The ‘habitable zone’ is an area around a star in which an orbiting planet’s surface could hold liquid water. The boundaries of the habitable zone are critical. If a planet is too close to its star, it will experience a runaway greenhouse gas effect, like Venus. But if it’s too far, any water will freeze, as is seen on Mars.A group led by San Francisco State University physicists searched through the list Kepler had returned to find those most likely to support life like our own. They found 216 Kepl...