NASA's Kepler mission's smallest habitable zone planet
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Scientists discover 'Earth-like' habitable planets

19 April 2013 Last updated at 07:23 BST

The US space agency Nasa says it has discovered two of the most habitable planets yet outside our solar system.

They are slightly larger than Earth and orbit a star 1,200 light-years away.

Scientists say these new worlds are the right size and distance from their parent star, so that you might expect to find liquid water on their surface.

Pallab Ghosh reports.