Scientists believe our solar system began 5 billion years ago when a nearby star exploded, sending a cloud of dust and gas that condensed into the Sun and 9 planets. The 9 planets - Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto - each have unique characteristics and formed as smaller pieces of the original cloud collided. The document provides a basic overview of how the solar system was formed and identifies the 9 planets and some of their distinguishing features.