Science NASA spacecraft passes Neptune's orbit en route to Pluto

New Horizons has passed another milestone: the NASA space probe has crossed the orbit of the outermost planet of our solar system as it speeds toward Pluto.

By , SPACE.com Senior Writer

Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

A speedy NASA probe has crossed the orbit of Neptune, notching one more spaceflight milestone on its way toward a historic flyby of Pluto next summer.