For the first time, scientists have discovered an Earth-sized alien planet in the habitable zone of its host star, an "Earth cousin" that just might have liquid water and the right conditions for life.

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The newfound planet, called Kepler-186f, was first spotted by NASA's Kepler space telescope and circles a dim red dwarf star about 490 light-years from Earth. While the host star is dimmer than Earth's sun and the planet is slightly bigger than Earth, the positioning of the alien world coupled with its size suggests that Kepler-186f could have water on its surface, scientists say.