This week on we're turning our attention to Pluto – what we used to think of as our ninth planet – and also to the mysterious new Planet 9 that might be orbiting on the outskirts of our solar system. We speak to Jeffery Moore, a research scientist at the NASA Ames Research Center, about what we've learned so far about Pluto from the New Horizons Mission. And we speak with Mike Brown, Professor of Planetary Astronomy at Caltech, about the search for Planet 9, and why we think there's another large planet out there revolving around our sun.