Planetary geologist Kirby Runyon is lead author of an abstract that proposes a new, geophysical definition of what a planet is.Learn more about your ad choices. Visit megaphone.fm/adchoices<p>See <a href="https://omnystudio.com/listener">omnystudio.com/listener</a> for privacy information.</p><p>See <a href="https://omnystudio.com/listener">omnystudio.com/listener</a> for privacy information.</p>

The Great American Eclipse—Be Part of It!

Planetary Radio brings you the human adventure across our Solar System and beyond. We visit each week with the scientists, engineers, leaders, advocates, and astronauts who are taking us across the final frontier. Regular features raise your space IQ while they put a smile on your face. Join host Sarah Al-Ahmed and Planetary Society colleagues including Bill Nye the Science Guy and Bruce Betts as they dive deep into space science and exploration. The monthly Space Policy Edition takes you inside the DC beltway where the future of the US space program hangs in the balance. Visit planetary.org/radio for an episode guide and much more.