2. What on Earth is Planet 9?

This week on Insult My Intelligence, Tim tackles his vast ignorance about the far edges of our solar system. He always thought Pluto was Planet 9 — but spoiler: it’s not. So is there a real ninth planet out there? To find out, Tim talks to Konstantin Batygin, the scientist behind today’s Planet 9 hypothesis, and astronomer Samantha Lawler, who has her doubts.