After a nine-year journey, a NASA space probe is nearing one of the solar system’s final frontiers.  Photo composite by Lon Tweeten for TIME. Sun: SDO; Mercury: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington; Earth, Neptune: NASA; Mars, Jupiter, Saturn: Universal History Archive/UIG/Getty Images; Uranus: NASA/JPL-Caltech

The Path to Pluto

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