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"Invisible" Alien Planet Kepler 19cCredit: David A. Aguilar (CfA)The "invisible" world Kepler-19c, seen in the foreground of this artist's conception, was discovered solely through its gravitational influence on the companion world Kepler-19b (the dot crossing the star's face). Kepler-19b is slightly more than twice the diameter of Earth, and is probably a "mini-Neptune." Nothing is known about Kepler-19c, other than that it exists.