The Solar System Trivia

The solar system is the one piece of astronomy almost everyone learns young and then slowly forgets the details of. The order of the planets, which one has the rings, why Pluto got demoted — it all blurs together after a while.

This quiz walks the neighborhood from the Sun outward and checks which facts actually stuck.

The Rocky Inner Planets and the Gas Giants

The four planets closest to the Sun are small, dense, and rocky. The next four are enormous balls of gas and ice with dozens of moons each. The dividing line runs right through the asteroid belt.

Why Pluto Isn't a Planet Anymore

In 2006 the International Astronomical Union settled on a definition of "planet" that Pluto didn't quite meet, since it hasn't cleared its orbital neighborhood of other objects. It's now classified as a dwarf planet, sharing that category with bodies like Eris and Ceres.

Distances That Are Hard to Picture

Light is the fastest thing there is, and it still takes about eight minutes to travel from the Sun to Earth. The same light needs more than five hours to reach Pluto.