If the International Astronomical Union approves the proposal, it will change not just that old saying but textbooks and toys and all the other things that rely on nine planets.

NPR: A Down-to-Earth View of the Planet Debate

For decades we've been told nine planets.

NPR: A Down-to-Earth View of the Planet Debate

First, its orbit appears to run in the opposite direction from those of the nine known planets.

ECONOMIST: X marks the spot

Pluto is the last of the nine familiar planets to be visited by a spacecraft and the program made a major discovery even before leaving the ground.

NPR: NASA Sends Spacecraft to Pluto

And then we just have to go: my very excellent mother just sent us nine pizzas with cheese, although there would be ten planets for nine pizzas.

NPR: A Down-to-Earth View of the Planet Debate

"Make no mistake about it, " said Geoffrey Marcy of San Francisco State University, who has helped find nine of the 12 planets discovered since 1995.

CNN: Astronomers spy new neighbors outside solar system

So there are eight planets in the solar system, not nine and not 10.

NPR: Pluto, the Un-Planet?