Lesson Outline for Teaching - Comprehensive Science 3

Lesson Outline for Teaching

Lesson 1: The Structure of the Solar System

A. What is the solar system? 1. The planets in the solar system orbit the Sun. 2. The Sun and the objects that orbit it make up the solar system.

B. Objects in the Solar System 1. The largest object in the solar system is the Sun. a. The Sun is a star made up mostly of hydrogen gas. b. Nuclear fusion produces enormous amounts of energy in the Sun. c. Objects orbit the Sun because it applies gravitational forces on them. 2. Objects that orbit the Sun include planets, dwarf planets, asteroids, and comets. These objects reflect the Sun's light. 3. A planet has a nearly spherical shape. a. The mass of a planet is much larger than the mass of nearby objects. b. There are eight planets in the solar system. c. The four planets closest to the Sun are called the inner planets. d. Inner planets are made mainly from rocky materials. e. The four planets farthest from the Sun are called the outer planets. f. Outer planets are made mostly of ice and gases. g. Because the outer planets are much larger than the inner planets, they are sometimes called gas giants. 4. A(n) dwarf planet is a spherical object that orbits the Sun, is not the moon of another planet, and has less mass than any of the eight planets. 5. Millions of small, rocky objects called asteroids orbit the Sun in a belt between Mars and Jupiter. 6. A(n) comet orbits the Sun in an oval-shaped orbit and is made of dust, gas, and ice. 7. The astronomical unit is used to measure long distances in the solar system. 8. One astronomical unit (AU) is the average distance from Earth to the Sun.

C. The Motion of the Planets 1. One way an object in the solar system moves is by orbiting, or revolving, around another object. 2. The amount of time it takes an object to revolve once around the Sun is its period of revolution. 3. Objects in the solar system also spin, or rotate.

Copyright ? Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.

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The Solar System

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4. The time it takes an object to rotate once is its period of rotation. 5. The shape of a planet's orbit is a(n) ellipse, which is a stretched-out circle.

a. The Sun is at one of the foci of the ellipse, so the distance between a planet and the Sun changes as the planet moves.

b. A planet moves faster when it is closer to the Sun than when it is farther away.

Discussion Question

If an asteroid is a sphere, could it be a planet? Explain your answer. The asteroid would be spherical, and it orbits the Sun. However, its mass would not be much larger than the mass of objects around it, so it could not be a planet.

Copyright ? Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.

The Solar System

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