The Outer Planets Plus One Amazing Asteroid

In the next century, scientists realized that anomalies in the orbit of Uranus could be accounted for by the presence of another planet. In 1846, after a search marked by total confusion (in keeping with the nature of the planet), European astronomers identified that unknown body and named it Neptune A third discovery further expanded the solar system in 1930, when Clyde Tombaugh, a 23-year-old amateur who was hired to examine photographic plates of the night sky, found what he was looking for A tiny, distant body, which is now named Pluto. 

When it was discovered, Pluto was hailed as the ninth planet. Since then, astronomers have discovered many small, icy, celestial objects orbiting the Sun. And so they ve begun to rethink what it means to be a planet. Is it enough to simply orbit the Sun Well, no. After all, asteroids revolve around the Sun, as do comets. Is it enough to be above a certain size Or to orbit the Sun from within the plane of the solar system By those standards, Pluto doesn tqual-ify. It s small, its orbit is tilted, and it has a peculiar gravitational relationship to its largest moon. 

The outer planets are also harbingers of change, both external and internal. These planets shake you up (revolutionary Uranus), inspire and confuse you (nebulous Neptune), and push you to the brink (take-no-prisoners Pluto). They represent the invincible, unstoppable, cosmic forces of change. 

---

Chapter 10 The Outer Planets (Plus One Amazing Asteroid)... 

---