NASA Principal Investigator for New Horizons mission Alan Stern (L) and Co-Investigator Will Grundy (R) hold up an enlarged, out-dated U.S. postage stamp with the words "PLUTO NOT YET EXPLORED", during the celebration of the spacecraft New Horizons flyby of Pluto, at NASA's Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, July 14, 2015. Also attending are APL Director Ralph Semmel (center,L) and Annette Tombaugh, daughter of Pluto's discoverer Clyde Tombaugh (center,R). The flyby, which culminated after almost ten years of flight and over three billion miles, will allow New Horizons to photograph and collect data in the coming months. REUTERS/Mike Theiler