Left to right: Nobel Peace Prize laureates President Ellen Johnson Sirleaf of Liberia, Liberian "peace warrior" Leymah Gbowee and Tawakkul Karman of Yemen.

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NPR's Philip Reeves

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Remnants of Tycho's Supernova, seen in an X-ray/infrared composite image. The supernova was observed by Tycho Brahe and other skywatchers in 1572.

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