Fun facts and trivia about the planet closest to the sun.

A beautiful but deadly planet.

The planet named after the god of war in Roman mythology.

The king of all planets -- bigger than all the other planets combined!

The planet known for its magnificent rings.

The sideways planet.

A planet which was discovered "mathematically."

Poor Pluto! Not a planet any longer!

Explanation of how planets are defined, how dwarf planets are defined, and the difference between the two.