Our Solar System...
Astronomers now recognize eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune), five dwarf planets (Ceres, Pluto, Makemake, Haumea, and Eris) , more than 150 moons, and many, many asteroids and other small objects (See the figure on the following page). These objects move in regular and predictable paths around the Sun. Distances in the Solar System Distances in the solar system are often measured in astronomical units (AU) . One astronomical unit is defined as the distance from Earth to the Sun. 1 AU equals about 150 million km (93 million miles). Listed below is the distance from the Sun to each planet in AU (Tablebelow) . The table shows how long it takes each planet to spin once on its axis. It also shows how long it takes each planet to complete an orbit. Notice how slowly Venus rotates! A day on Venus is actually longer than a year on Venus! Our solar system is about 100,000 AU across from the Sun to the Oort Cloud or 1.87...