Unless you’re living under a rock, you’ve probably already heard of this. The International Astronomical Union, aka the Committee on What to Call Astronomical Stuff, has today adopted an official definition of what is — and isn’t — a planet, in the process stripping Pluto of the title it has held since its discovery in 1930. Pluto has now been reclassified as a dwarf planet, meaning our solar system has 8 proper planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.

Our new solar system .