Coming soon: First encounter with a new class of worlds​

After an epic journey across the breadth of the solar system, the New Horizons spacecraft is finally nearing its destination: the Pluto system, a staggering three billion miles from Earth. William McKinnon, a planetary scientist at Washington University in St. Louis, explains that our understanding of Pluto has been transformed in the nearly 10 years the probe has been en route to its target. ​