Name Lesson 1 Summary Use with pp. 455–457 Lesson 1: What are the parts of the solar system? Vocabulary planet a large body of matter that revolves, or travels, around the Sun solar system the Sun, the nine planets and their moons, and other objects that revolve around the Sun orbit the path an object takes as it revolves around the Sun asteroids chunks of rock of different sizes that orbit the Sun The Sun Look at pages 456–457 in your textbook. The Sun is a star. It is made of hot, This picture shows each planet’s orbit. An burning gases. The Sun looks larger and orbit is the oval-shaped path each planet brighter than other stars because it is much takes as it revolves around the Sun. Planets closer to Earth. The Sun is very big. It is 100 that are closer to the Sun have shorter times as wide as Earth. The Sun is so big that orbits. The strong pull of gravity holds the it could hold one million Earths inside it! planets in their orbits. The temperature of the Sun’s surface The planets that are closer to the Sun is 5,500oC. The center of the Sun is even are called the inner planets. These are hotter. The Sun’s gravity packs hot gas Mercury, Venus, Earth, and Mars. Mercury particles together very tightly, and they join is the planet closest to the Sun. It is about together. This gives the particles a lot of 58 million kilometers from the Sun. Outer energy. The Sun gives off energy that moves planets are farther from the Sun. The five in all directions. Some of the Sun’s energy outer planets are Jupiter, Saturn, Uranus, reaches Earth as sunlight. Neptune, and Pluto. Pluto is the farthest planet from the Sun. It is usually about 5 How Objects in the Solar billion kilometers from the Sun. System Move Asteroids are also part of the solar We live on the planet Earth. A planet system. Asteroids are chunks of rock objects is a large body of matter. Planets revolve of different sizes. Asteroids orbit the Sun around the Sun. The solar system is between the planets. Most asteroids are made of the Sun, nine planets, the planets’ between Mars and Jupiter. moons, and other objects that revolve © Pearson Education, Inc. 3 around the Sun. 104 Chapter 16, Lesson 1 Summary Quick Study
Name Lesson 1 Checkpoint Use with pp. 455–457 Lesson 1 Checkpoint 1. Why is the Sun so bright and hot? 2. What makes up the solar system? 3. How do objects in the solar system move? © Pearson Education, Inc. 3 Quick Study Chapter 16, Lesson 1 Checkpoint 105
Name Lesson 2 Summary Use with pp. 458–465 Lesson 2: What are the planets? The Inner Planets Earth’s rocky surface is made of sections Mercury, Venus, Earth, and Mars are the called plates. These are on land and under four inner planets. These planets are closer the sea. These plates are always moving. to the Sun than the outer planets. The Sometimes, they slide past each other. inner planets are rocky. They do not have Sometimes plates bump into each other, rings around them, and they do not have causing earthquakes or volcanoes. The many moons. plates keep changing Earth’s surface. The inner planets are of different sizes. The Gas Giants Mercury, the second smallest planet, is dry, The five outer planets are Jupiter, Saturn, very hot, and has many craters. Venus, a Uranus, Neptune, and Pluto. They are little smaller than Earth, is also a very hot, much farther apart than the inner planets. rocky planet with craters, mountains, and Most of the outer planets are huge and are valleys. Mars is the “Red Planet” because of called gas giants. This is because the outer its reddish-orange, rocky, dusty surface. It is planets are mostly made of gases. Jupiter half the size of Earth. Earth, the third planet and Saturn are the two largest gas giants. from the Sun, is a little larger than Venus. The outer planets are different from the The inner planets rotate at different speeds. inner planets in two other ways. The outer For example, it takes Earth 24 hours to rotate planets have rings around them. Also, most once. But it takes Venus 243 days to rotate. of these planets have many moons. Like The inner planets revolve around the Sun the inner planets, most of the outer planets at different speeds. Mercury takes 88 days rotate at different speeds around the Sun. while Earth takes 365 days to travel around the Sun. Uranus, Neptune, and Pluto Earth Supports Life Uranus and Neptune are about the same size. They are smaller than Saturn and Earth is very different from the Jupiter. But they are much bigger than other planets. It is the only planet that the inner planets and Pluto. Pluto is the can support life. Earth has the mild smallest planet in the solar system. It is the temperatures, water, and atmosphere that only outer planet that is not made of gas. living things need. Earth’s atmosphere has the right amounts of oxygen and carbon Is It a Planet? dioxide. The atmosphere also protects us In 2004, scientists discovered a tenth from the Sun’s dangerous rays. Earth’s planet they called Sedna. It is much farther gravity holds the atmosphere close to Earth. from the Sun than Pluto. Sedna is smaller Sunlight warms Earth and gives plants than Pluto. Many scientists, however, do energy to grow. But not all of the Sun’s light not think Sedna is a real planet. Scientists reaches Earth’s surface. The atmosphere have found other small objects beyond © Pearson Education, Inc. 3 soaks up some of this light. Some light Pluto. They call Sedna and these objects reflects off the ground and clouds. Gases “planetoids.” in the atmosphere scatter this light. This makes the sky look blue. 106 Chapter 16, Lesson 2 Summary Quick Study
Name Lesson 2 Checkpoint Use with pp. 458–465 Lesson 2 Checkpoint 1. Which of the nine planets are inner planets? 2. Compare and Contrast How do the sizes of the four inner planets compare? 3. What makes life on Earth possible? 4. In what ways are Jupiter and Saturn alike? 5. Which of the nine planets are outer planets? 6. Which of the outer planets is not a gas giant? © Pearson Education, Inc. 3 7. Compare and Contrast On a two-column chart, list the ways that the inner planets and the gas giants are alike and different. Quick Study Chapter 16, Lesson 2 Checkpoint 107