Planetary Radio • Mar 08, 2017

Hope for Pluto—Should We Re-Redefine Planets?

Please accept marketing-cookies to listen to this podcast.

Download MP3

On This Episode

Kirby runyon portrait

Kirby Runyon

Planetary geologist and research scientist at the Planetary Science Institute

Planetary geologist Kirby Runyon is lead author of an abstract that proposes a new, geophysical definition of what a planet is. It would grant our solar system 110 planets, including Pluto and the moon. Up, up and away with Digital Editor Jason Davis on World View’s balloon ride to just below the edge of space. It’s the asteroid of love and it’s the destination of this week’s space trivia contest. Bill Nye has the week off.

High-resolution enhanced-color global MVIC portrait of Pluto
High-resolution enhanced-color global MVIC portrait of Pluto This beautiful high-resolution image of Pluto is from a single observation with the MVIC imager on the Ralph instrument. It is an enhanced-color view made of three images captured through infrared, red, and blue filters. The three individual images were denoised, deconvolved, and enlarged by a factor of 2 before being combined into this stunning portrait.Image: NASA / JHUAPL / SwRI

Related Links:

This week's prizes are a Planetary Radio t-shirt, now available in both men’s and women’s styles. Also, a 200-point astronomy account, and a Planetary Society rubber asteroid.

This week's question:

What is the diameter of the primary mirror on the great observatory on the Spitzer Space Telescope?

To submit your answer:

Complete the contest entry form at or write to us at [email protected] no later than Wednesday, March 15th at 8am Pacific Time. Be sure to include your name and mailing address.

Last week's question:

Several spacecraft landing sites on Mars are designated as memorials. What is the designation of the Viking One memorial site?


The answer will be revealed next week.

Question from the week before:

Where in the solar system would you find a crater named Valentine, after Saint Valentine?


The only crater officially designated with the name Valentine is on asteroid 433 Eros, visited by the NEAR Shoemaker probe.