WAUKESHA, WI – Will Pluto remain a planet? It’s certainly the most compelling question to come out of the International Astronomical Union’s (IAU) attempt to define what, exactly, “planet” means.

School children will have to take the “P” out of whatever mnemonic they use to help them remember the solar system’s planet lineup. That’s because astronomers decided on Thursday to nix Pluto from the ...

At a recent American Astronomical Society meeting, UCLA Professor of Planetary Astronomy Jean-Luc Margot shared a simple test that can clearly separate, and allow us to easily distinguish, planets, ...