200: Pluto is a planet, and so is its moon with Dr. Runyon
Release Date:
Dr. Kirby Runyon shares his definition of "planet"-- a round celestial body that was never a star. Using this definition, there are over 150 planets orbiting our sun. He explains why the word planet matters, and why little planets might be the most common planets in our universe.
200: Pluto is a planet, and so is its moon with Dr. Runyon