Artist's concept compares Earth (left) to the new planet, called Kepler-452b, which is about 60 percent larger in diameter. NASA/JPL-Caltech/T. Pyle hide caption

itoggle caption NASA/JPL-Caltech/T. Pyle

The SpaceX Falcon 9 rocket and Dragon spacecraft break apart shortly after liftoff from the Cape Canaveral Air Force Station in Cape Canaveral, Fla., on June 28. SpaceX CEO Elon Musk said Monday the failure of a steel strut likely caused the rocket to explode. John Raoux/AP hide caption

itoggle caption John Raoux/AP

Members of the New Horizons science team react to seeing the spacecraft's image of Pluto on Tuesday, before its closest approach. Bill Ingalls/NASA via AP hide caption

itoggle caption Bill Ingalls/NASA via AP

In the center left of Pluto's vast heart-shaped feature – informally named "Tombaugh Regio" — lies a vast, craterless plain that appears to be no more than 100 million years old, and is possibly still being shaped by geologic processes. NASA/JHUAPL/SWRI hide caption

itoggle caption NASA/JHUAPL/SWRI

Harry Kroto, pictured in 1996, displays a model of the geodesic-shaped carbon molecules that he helped discover. Michael Scates/AP hide caption

itoggle caption Michael Scates/AP

An image of Pluto that was taken by New Horizons shortly before its flyby Tuesday shows a heart-shaped pattern on the planet's surface. NASA says Pluto "sent a love note back to Earth." NASA/Johns Hopkins Applied Physics Laboratory/Southwest Research Institute hide caption

itoggle caption NASA/Johns Hopkins Applied Physics Laboratory/Southwest Research Institute