Pluto in Grandma's Living Room
Pale Blue Pod
00:00
Planets and Astronomy
The word planet comes to us from an ancient like Greek word, meaning wanderer. In 2006, the International Astronomical Union laid out three different criteria for what a planet was. The body has to be massive enough that its gravity has cleared away other objects of similar size near its orbit. Pluto fails on this third criterion and is now considered a dwarf planet.
Transcript
Play full episode
