Chapter 17 Lesson 2

What are the parts of the solar system?

Objectives

• The student lists and describes the different objects in the solar system.

• The student knows that the planets differ in size, characteristics, and composition and that they orbit the Sun in our Solar System.

• The student knows the arrangement of the planets and the asteroid belt in our Solar System.

What are the parts of the solar system?

• You probably know your home address and those of your closest neighbors. If you were to write your space address, you might add, "Planet Earth, Solar System, Milky Way Galaxy." The solar system contains seven other neighboring planets and other objects.

Earth

The Planets’ Orbits• Planets closest to the Sun travel fastest in their orbits. Their

orbits are also the smallest, so they can make a revolution most quickly. Planets farther away move more slowly and their orbits are longer, so their revolutions take many Earth years. In the solar system, distances are so great that scientists use a measure called Astronomical Units, or AU. One AU is the average distance between Earth and the Sun.

Explain

• Why do planets have years of different lengths?

Neptune

Cause and Effect

• What causes a year on Mercury to be less than 365 Earth days?

Mercury

The Inner Planets

Earth Mercury

Venus Mars

The Gas Giants

Beyond Neptune

• Far beyond the orbit of Neptune is an area of the solar system called the Kuiper (pronounced Ky'per) Belt. It contains thousands of icy, rocky objects known asKuiper Belt Objects, or KBOs for short. The dwarf planetPluto and its moon Charon are KBOs. Some KBOs arelarger than Pluto and are also classified as dwarf planets.

Pluto Charon

Independent Practice

Before next class …• Read and carefully review Chapter 17 Lesson 2 in

your Science textbook, pages 548 through 551.• Complete the Chapter 17 Lesson 2 homework

assignment on the EdMastery website.