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Planetary RadioJuly 14, 2015

A Small, Distant World: Kepler 138b

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On This Episode
Jason Rowe head shot
Jason Rowe

Research Scientist, SETI Institute

SETI Institute scientist Jason Rowe returns to tell us about the smallest exoplanet so far that has had its size and mass determined. Jason also talks with Mat about our ever-expanding knowledge of these worlds that circle faraway stars. Emily Lakdawalla and Bill Nye report from the New Horizons control center just hours before the spacecraft has its historic encounter with Pluto. Plutomania continues with Bruce Betts and this week’s What’s Up segment.

Kepler 138b

Danielle Futselaar, SETI Institute

Kepler 138b
An artist’s conception of what Kepler 138b, its sister planets and its star might look like.

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This week's question:

What was the last year in which Pluto was closer to the sun than Neptune?

To submit your answer:

Complete the contest entry form at or write to us at no later than Tuesday, July 21st at 8am Pacific Time. Be sure to include your name and mailing address.

Last week's question:

What was the mass of the plutonium flown on New Horizons?


The answer will be revealed next week.

Question from the week before:

Of the five moons of Pluto known before New Horizons, which two moons have a mythological family relationship?


There are two acceptable answers to our question about mythological family relationships among the five moons of Pluto. Nix is the mother of Charon, and Cerberus is the sibling of Hydra.

Listen more: New Horizons, Pluto, Charon, mission status, Planetary Radio, extrasolar planets, Bill Nye

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