Pluto and Beyond What Lies at the Edge of the Solar System?

Somewhere far beyond the orbit of Neptune, a spacecraft about the size of a grand piano is coasting through the dark. Bolted inside it is a small container holding a portion of the ashes of a Kansas farm boy named Clyde Tombaugh. He found Pluto in 1930. After the spacecraft flew past that world, it kept going, carrying him with it into a region that astronomers had barely begun to map while he was alive.

Tombaugh's story is bound up with one of the stranger turns in modern science. The world he found was celebrated for three-quarters of a century as the ninth planet, then removed from the list by a vote. Yet the demotion did not shrink Pluto. It revealed that Pluto was a resident of a vast, crowded, icy frontier, and that the edge of the solar system is far more interesting than a lonely last planet at the end of the line.

This is a journey outward through that frontier, from the orbit of Neptune to the place where the Sun's influence finally gives out.