Michael E. Brown is a professor of planetary astronomy at the California Institute of Technology. His 2012 book is called How I Killed Pluto and Why It Had It Coming. He helped discover our solar system's Kuiper Belt, which is similar to the asteroid belt, but containing up to 200 times more material. It extends from the orbit of the 8th planet, Neptune, to about 50 times Earth's distance from the sun. In early 2016, Brown and a colleague - Konstantin Batygin, also at Caltech - described how the similar orbits of six small bodies in the outer solar system could be explained by another major planet in our solar system. They call it Planet Nine. And they're still hoping to find it.
