Understanding the New Solar System

The solar system - our sun and the planets and other bodies that orbit it - has remained essentially the same for hundreds of millions of years. What could possibly be new about the solar system? Quite simply, our knowledge of what truly makes up the solar system and our deeper understanding of long-known objects such as the planets and their satellites, comets, and asteroids are changing constantly. The ancient Romans observed and noted the motions of the known planets. But Uranus was not discovered until 1781, Neptune in 1846, and Pluto in 1930. Pluto's moon, Charon, was only discovered in 1978, about the same time that robotic exploration of the solar system became a serious undertaking.