Expository Text PAIRED. Why the Stars Twinkle READ

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1 Expository Text Destination Saturn by Karen Alexander PAIRED READ Why the Stars Twinkle

2 STRATEGIES & SKILLS Comprehension Strategy: Summarize Skill: Main Idea and Key Details Vocabulary Strategy Suffixes Vocabulary amount, astronomy, globe, solar system, support, surface, temperature, warmth Content Standards Science Earth and Space Science Word count: 1,113** Photography Credit: Cover NASA/JPL/Space Science Institute. **The total word count is based on words in the running text and headings only. Numerals and words in captions, labels, diagrams, charts, and sidebars are not included. Copyright The McGraw-Hill Companies, Inc. All rights reserved. No part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written consent of The McGraw-Hill Companies, Inc., including, but not limited to, network storage or transmission, or broadcast for distance learning. Send all inquiries to: McGraw-Hill Education Two Penn Plaza New York, New York ISBN: MHID: Printed in the United States DOC A

3 Essential Question What do we know about Earth and its neighbors in space? Destination Saturn by Karen Alexander Chapter 1 Exploring Saturn Chapter 2 Mission to Saturn Chapter 3 Storm on Saturn Respond to Reading PAIRED READ Why the Stars Twinkle Glossary/Index Focus on Science

4 Chapter 1 Exploring Saturn People have been studying the stars and planets for thousands of years. This study is called astronomy. Even before telescopes were invented, people had found the planet Saturn. With the help of spacecraft, we are learning new things about Saturn. Saturn is the second biggest planet in our solar system. It is also the sixth planet from the sun. Neptune Uranus Saturn Jupiter Mars Earth Venus Mercury 2 The Solar System Sun Stocktrek/Alamy

5 Saturn is many times bigger than Earth. Saturn Earth Saturn doesn t look like a globe. It looks as if someone has pushed the top and bottom of a ball together. It looks like this because it rotates fast. Saturn has a rocky center, but its surface is gas. It could not support human life. (tl) NASA/JPL/Space Science Institute, (tr) NOAA/NASA GOES Project Gas Planet Saturn is a gas planet. The rock at its center is probably so hot that it is liquid. Jupiter, Uranus, and Neptune are gas planets, too. Gas planets are much bigger than planets that are made up of metal and rock, such as Earth. Those are called terrestrial planets. 3

6 The Rings of Saturn Saturn is the easiest planet to recognize because of its rings. All the gas planets have rings, but Saturn s are the biggest and most noticeable. The rings are mainly ice, with bits of rock and dust. The pieces vary in size. Some are the size of a grain of sand. Some are the size of a mountain. The rings extend thousands of miles from Saturn. However, they are only about half a mile thick. Scientists think that Saturn s rings might have formed from pieces of moons that had broken up. Saturn s rings 4 NASA/JPL/Space Science Institute

7 Eight groups of rings have been discovered so far. They were named in alphabetical order as they were discovered. There are many rings in each group, and gaps between Did You Know? the rings. If Saturn were put in a huge pond, it would float. Library of Congress Prints and Photographs Division [LC-USZ ] Discovering the Rings The astronomer Galileo was the first person to look at Saturn through a telescope and see Saturn s rings. Galileo could not see exactly what the rings were. He drew them as if they were handles. Huygens, a Dutch astronomer, worked out that the shape was a ring. Galileo The astronomer Cassini realized that there were at least two rings. The space between Rings A and B is now called the Cassini Division. 5

8 Many Moons Earth has just one moon. Saturn, however, has many moons. Fifty-three of them have names, but more are being discovered all the time. Titan was the first moon to be discovered. It is also the biggest. In fact, it is bigger than the planet Mercury. The moons are all different. Many moons are icy. Some are huge. Some are tiny. Some even have their own rings. The moon Phoebe travels around Saturn in the opposite direction from the way Saturn travels. Phoebe Saturn 6 NASA/JPL- Caltech

9 Dione is one of Saturn s icy moons. Some of Saturn s rings can be seen behind Dione. Dione Did You Know? A day on Saturn is 10 hours and 39 minutes, in Earth time. A year is 29.5 Earth years. NASA/JPL/Space Science Institute Some of the moons orbit inside the rings. They are called shepherd moons. That is because the force of gravity between them and the rings can move the rings around. Two of the moons share the same orbit. They travel within 30 miles of each other. Every four years, the outside one catches up with the inside one and they swap places. 7

10 Chapter 2 Mission to Saturn Scientists have been learning more about Saturn with the help of spacecraft. In 1997, a space mission left Earth to study the planet and its moons and rings. The Cassini-Huygens spacecraft took seven years to travel from Earth to Saturn. The spacecraft orbited Saturn, and sent information about the planet back to Earth. It then divided into two. One part, Huygens, landed by parachute on Titan. Its instruments sent information and images of Titan back to Earth. Did You Know? When the mission began in 1997, only 18 of Saturn s moons had been discovered. The Cassini mission found some more. Others were discovered with the use of improved telescopes. 8 NASA

11 This is an artist s impression of the Huygens spacecraft landing on Titan. Craig Attebery/NASA The Long Way Round Saturn is 800 million miles from Earth, but the Cassini-Huygens spacecraft went a lot farther than that to get there. It traveled about two billion miles. Why? A spacecraft cannot carry enough fuel for such a long journey. However, gravity is helpful in space travel. The spacecraft flew past Earth, Venus, and Jupiter. These fly-bys helped it to build up speed. For most of the voyage, the spacecraft floated through space without using its engines. When the spacecraft got to Saturn, it used its engines to slow down enough to enter Saturn s orbit. 9

12 The Cassini-Huygens spacecraft discovered a huge amount of exciting information about Titan. Astronomers think that Titan might be like Earth was when it was young. It is the only moon in our solar system that has clouds and an atmosphere. Photos taken by the spacecraft show that the landscape of Titan is similar to that of Earth. Titan has river valleys and mountains. Titan might also have weather patterns that are like those on Earth, with rain and wind. The surface of Titan is much too cold for any water to be liquid. However, scientists think there may be an ocean under the surface. This painting of Titan s surface is based on information sent by the Cassini-Huygens spacecraft. 10 NASA/JPL

13 (t) Cassini Imaging Team, NASA/JPL/SSI, (b) Steven Hobbs/NASA/JPL The mission found out about other moons, too. Hyperion looks like a jagged piece of rock. Its shape is very unusual. Most objects that rotate in space are basically round. Hyperion Huygens was the first spacecraft to land anywhere in the outer solar system. Cassini Huygens 11

14 Icy vapor rises from Enceladus. Saturn is a long way from the sun. The planet and its moons get much less sun than Earth gets. The moon Enceladus looks bright because it is covered with ice. The ice reflects the sunlight back into space. Jets of icy water spray from Enceladus. Instruments in the Cassini spacecraft tested the water and found that it is like Earth s oceans. Scientists believe this may mean there is liquid salt water beneath the moon s crust. There is also warmth on Enceladus. Scientists think the warm temperature means there is heat deep inside Enceladus. 12 NASA/JPL

15 Chapter 3 Storm on Saturn When the Cassini mission ends in September 2017, the spacecraft will have been at Saturn for nearly half a Saturn year. One of the more amazing events of the mission has been to track a huge thunderstorm on Saturn. The storm stretches around the whole planet, sending streams of gas into Saturn s atmosphere. The storm covers an area eight times greater than the area of Earth. Scientists say it is much more powerful than any storm on Earth. Scientists find it exciting to see the storm on Saturn because storms on Saturn are rare. NASA/JPL 13

16 Saturn People study astronomy for many reasons. They want to find out more about the universe. They also want to see if there is life on any other planet or moon. The Cassini mission has already revealed a great deal about Saturn. Some of the most exciting information relates to the moons Titan and Enceladus. Titan may teach us more about Earth when it was a young planet. Enceladus has warmth and water, two cornerstones of life. Who knows what other amazing discoveries will be made in the future! 14 NASA/JPL/Space Science Institute

17 Summarize Summarize what you have learned about Saturn. Use the Main Idea and Key Details Chart to help you. Main Idea Detail Detail Detail Text Evidence 1. How do you know that Destination Saturn is an expository text? GENRE 2. Reread page 10. Why are scientists interested in Titan? MAIN IDEA AND KEY DETAILS 3. What does icy on page 12 mean? Rewrite the sentence using ice instead of icy. SUFFIXES 4. Write about why the mission to Saturn is important. Use details from the text to support your answer. WRITE ABOUT READING 15

18 Compare Texts You have read about a space mission to Saturn. Now learn how people used to explain the universe. WHY THE STARS TWINKLE Long, long ago, Earth and the sky were not far apart, as they are now. They were close together. People on Earth could touch the sky. One day, a woman went outdoors to grind rice for her family s meal. The woman had lovely, long, silky hair. She spent a great deal of time brushing it. She was also very proud of her jewelry, and wore it even when she was working. It was a hot day, and the woman didn t want to be working. She put a large amount of grain into a wooden bowl so she could grind it all at once. She started to smash it with a heavy tool called a pestle. It was hard work. The woman got angry. 16 Illustration: Pamela Becker

19 Each time the woman pounded the rice, she raised the pestle higher. As she worked, she got a blister where her gold ring rubbed the skin on her finger. She took off the ring and hung it on the sky. The silver comb in her hair fell out. That made her angrier. She hung her comb on the sky. Then her necklace got in the way of the pestle, so she hung that on the sky, too. Each time the woman raised the pestle, she pushed the sky farther away. She was so busy that she didn t realize what was happening. 17

20 At last, the woman finished her work. She wiped her brow and stood back. As she did, she felt air brush her face. She looked up to find that the sky was now far, far above her. Away in the distance, she could see her ring, comb, and necklace, but she couldn t reach them. You can still see her jewelry. Her silver comb became the moon, and her gold ring became the sun. Her sparkly necklace became the stars that twinkle across the surface of the sky. Illustration: Pamela Becker Make Connections Why do you think Why the Stars Twinkle was written? ESSENTIAL QUESTION In what way does the explanation for the stars, moon, and sun in Why the Stars Twinkle differ from the descriptions of space in Destination Saturn? TEXT TO TEXT 18

21 Glossary astronomer (uh-strah-nuh-muhr) a person who studies the stars and planets (page 5) atmosphere (AT-muh-sfir) the gases that surround a planet (page 10) gravity (GRA-vuh-tee) the natural force that pulls objects toward one another (page 7) orbit (AWR-buht) to follow a path, usually circular, around a planet, moon, or other space body (page 7) terrestrial planets (tuh-res-tree-uhl PLA-nuhtz) planets made of rock and metal (page 3) Index Enceladus, 12, 14 Hyperion, 11 moons, 4, 6 8, 10 12, 14 rings, 4 8 telescopes, 2, 5, 8 Titan, 6, 8 10, 14 19

22 Purpose To find out the differences and similarities between two planets. What to Do Step 1 Choose a planet that you are interested in not Saturn. Step 2 Find out as much as you can about the planet. Where is it in the solar system? How big is it? Does it have any interesting features? Step 3 Make a Venn diagram comparing your planet with Saturn. Different Alike Conclusion What can you learn by comparing and contrasting two planets in this way? 20

23 Literature Circles Nonfiction The Topic What are Destination Saturn and Why the Stars Twinkle mostly about? Vocabulary Did you learn any new words? If so, what helped you understand the meaning of these words? Conclusions What conclusion can you draw from the information in Destination Saturn? Author s Purpose Why do you think the author wrote Destination Saturn? Why do you think the author paired a legend with an expository text?

24 Discover the Universe Science GR N Benchmark 30 Lexile TK Grade 3 Unit 3 Week 3 ISBN MHID EAN