All seven planets are rocky worlds, ranging from about the size of Mars to a little larger than Earth .
Three or four of them reside within their star's habitable zone, meaning they orbit at the right distance to support liquid water on their surfaces.
Publisher: Space.com
Date: 2017-02-23T07:12:35Z
Author: Keith Cooper
Twitter: @SPACEdotcom
Reference: (Read more) Visit Source
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