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1 Suggested levels for Guided Reading, DRA, Lexile, and Reading Recovery are provided in the Pearson Scott Foresman Leveling Guide. Space and Technology The Solar System and Beyond by Jen Coates-Conroy Genre Expository nonfiction Comprehension Skills and Strategy Draw Conclusions Fact and Opinion Visualize Text Features Captions Diagrams Labels Glossary Scott Foresman Reading Street ì<(sk$m)=bdgegj< +^-Ä-U-Ä-U ISBN

2 The Solar System and Beyond by Jen Coates-Conroy Editorial Offices: Glenview, Illinois Parsippany, New Jersey New York, New York Sales Offices: Needham, Massachusetts Duluth, Georgia Glenview, Illinois Coppell, Texas Ontario, California Mesa, Arizona

3 Exploring the Solar System Our solar system includes our sun and nine planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. Seven of the planets, all of them except for Venus and Mercury, have one or more moons that orbit them. Scientists are still not sure how many moons each of the planets has. With each new study of space, it seems scientists continue to learn about new moons. The solar system also includes thousands of asteroids, which are rocky objects, smaller than planets, that orbit the sun. Countless comets also fly through the solar system. Every effort has been made to secure permission and provide appropriate credit for photographic material. The publisher deeply regrets any omission and pledges to correct errors called to its attention in subsequent editions. Unless otherwise acknowledged, all photographs are the property of Scott Foresman, a division of Pearson Education. Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd) Opener: Corbis; 3 Ariel Skelley/Corbis; 8 Denis Scott/Corbis; 9 Roger Ressmeyer/Corbis; 10 Corbis; 11 NASA; 12 Getty Images; 15 (T) Sanfor/Agliolo/Corbis, (B) Dennis di Cocco/ Corbis; 16 Underwood & Underwood/Corbis; 18 Corbis; 22 Roger Ressmeyer/Corbis ISBN: Copyright Pearson Education, Inc. All Rights Reserved. Printed in the United States of America. This publication is protected by Copyright, and permission should be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic, mechanical, photocopying, recording, or likewise. For information regarding permission(s), write to: Permissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois V0G

4 For thousands of years, humans have wondered about the sky above and tried to explain it. They invented universal stories to explain what they saw until they found ways to study space from a scientific point of view. As time went on, the means of exploring our solar system evolved from the human eye, to the telescope, to the spaceship and satellite, and finally to the space station. The United States has played a major role in space exploration. In 1969, American astronauts traveled to the moon. They brought back a knowledge and understanding of our solar system that no one on Earth had ever had before. Even before taking steps on the moon, countries were racing to better understand our universe. On October 4, 1957, the Soviet Union placed the first satellite, Sputnik 1, into orbit around Earth. Fifteen months later, the Soviet Union s Luna 1 became the first craft to escape Earth s gravity and enter an orbit around the sun. On April 12, 1961, Soviet Yury Gagarin became the first person to venture into space. A replica of the Soviet satellite Sputnik 1 is displayed for people to see in Moscow in With all of these achievements, the Soviet Union leapt ahead of the rest of the world in space exploration. But the United States was not far behind. Just over eight years after Gagarin made his the first trip into space, Neil Armstrong, Michael Collins, and Buzz Aldrin made it to the moon. On July 20, 1969, Commander Neil Armstrong became the first person to walk on the moon. He spoke the historic words: That s one small step for man, one giant leap for mankind. Since 1969, twelve American astronauts have walked on the moon. Today over two hundred astronauts, including the first African American, Guion S. Bluford Jr., and first American woman, Sally K. Ride, have traveled into space. Why do we continue to explore our solar system and beyond? Space exploration may provide us with clues to our existence. Astronomers and physicists have more questions than answers about our solar system. American Achievements in Space May 5, 1961 Alan B. Shepard Jr. is the first American in space. February 20, 1962 John H. Glenn Jr. is the first American to orbit Earth. July 20, 1969 Neil A. Armstrong is the first person to walk on the moon. July 15 24, 1975 Donald K. Slayton is the first American to dock with a foreign spacecraft. June 18, 1983 Sally K. Ride is the first American woman in space. August 30, 1983 Guion S. Bluford Jr. is the first African American in space. 4 5

5 In 1971, the Soviet Union launched a space station called Salyut 1. This space station allowed scientists to stay in space for long periods of time and conduct experiments. In 1973, the United States launched Skylab, the first American space station. Today, space programs from the United States, Russia, and other countries are working together to build the International Space Station. It will be a barge in space for countries to use and work from together. Satellites and space stations allow us to study our solar system more closely. For example, studies of materials from near the planets suggest that the solar system is almost 4.6 billion years old. Scientists believe that our solar system may have begun as a vast cloud of gas and dust, or nebula. This nebula was disturbed by something perhaps a shock wave from the explosion of a nearby star. Such a shock wave could make the nebula collapse. The nebula could have grown hotter and denser in the center. The nebula s center then heated up enough to become a star, the sun. Skylab was the first American space station that was launched into orbit around Earth. 6 7

6 The Sun The sun is the center of our solar system. We could not survive on Earth without it. The sun is a large ball of extremely hot, molten gases. About 109 Earths could fit across the face of the sun. It contains over ninety-nine percent of all material in the solar system. Like other stars, the sun is not a solid object, but we can detect a visible surface called the photosphere. The temperature there is hotter than 9,930 degrees Fahrenheit. About three-fourths of the sun is hydrogen. The rest is mostly helium with small amounts of other elements. Gravity keeps the gases together, pulling them toward the sun s center. Earth is about 93 million miles from the sun. However, the sun s rays that hit our planet are still very powerful. Astronomers study the sun by using special telescopes. The Many Moons of the Solar System Space probes have given us information about the moons in our solar system. Each moon is like a rock covered with ice. There are ice volcanoes, frozen oceans, sulfur spurts, red-hot lava, grooves, and craters. Earth s moon orbits around us at a distance of approximately 238,400 miles. It journeys with Earth as it makes its yearly orbit around the sun. The moon is a cold, lifeless ball of rock about one-fourth the size of Earth. It doesn t have an atmosphere and it is covered with craters. Six other planets have one or more moons orbiting them. Jupiter, the largest planet in the solar system, has sixty-three known moons! Scientists are still not sure if they have discovered them all. Saturn and two of its moons 8 9

7 Scientists have discovered that Jupiter s moon Io has the hottest, most active volcanoes in our solar system. The Ulysses spacecraft, a joint mission of the National Aeronautics and Space Administration (NASA) and the European Space Agency, spotted the moon in It took pictures and sent them back to Earth. As Ulysses approached Jupiter, it was hit with volcano dust. The dust came in a tight stream, like water from a garden hose. It moved extraordinarily fast at 670,000 mph! Scientists have discovered thirty-four moons orbiting Saturn, the second largest planet in the solar system. Two of Saturn s moons were discovered as recently as August But moons are not the only things that can be found circling Saturn. Voyager 2 took pictures of Uranus and its blue rings as it rose above the horizon of its cratered moon, Miranda. The Ringed Planets Saturn, along with Jupiter, Uranus, and Neptune, has a series of rings. There are actually tens of thousands of thin rings around Saturn. Each ring is made up of tiny bits of ice-covered particles. Some scientists believe that the particles are small bits of ore. The elements in the rings give them their distinctive colors. The rings around Uranus are very different. They are also believed to be younger than those around Saturn. They are made of a darker material that is harder to see. In some places, the rings are so thin that they disappear altogether. Voyager 1 took photos of Jupiter and its orbiting moons

8 Saturn Jupiter Earth Uranus Venus Mercury Pluto Mars Neptune The Planets in Orbit All nine planets move counterclockwise around the sun. The time it takes a planet to complete a full orbit is the length of its year. Mercury, the planet closest to the sun, takes only eighty-eight Earth days to complete a full orbit. One year on Mars, the fourth planet from the sun, is almost as long as two Earth years. It takes 248 Earth years to equal one year on Pluto, because it is the farthest planet from the sun. Earth takes 365 and one-quarter days to complete an orbit around the sun. Planets travel in elliptical, or oval-shaped, paths. However, not all orbits are the same. Neptune s orbit is nearly circular. Pluto s orbit is very irregular. Because of this, every 248 years these planets cross paths and switch places. For a period of twenty years, Pluto becomes the eighth planet from the sun and Neptune becomes the ninth. What keeps all nine planets in our solar system? Gravity holds the planets in orbit around the sun and keeps the solar system together. The sun is a very dense star. Its total mass is 743 times that of all the other planets put together. It pulls the planets, asteroids, and comets into orbit around it because it is the most dense object in the solar system

9 Asteroids and Comets Asteroids and comets are smaller members of the solar system family. The first asteroid was discovered by an Italian astronomer named Giuseppi Piazzi on January 1, He named it Ceres. Since then, thousands of asteroids have been discovered. Asteroids are minor planets that orbit the sun between Mars and Jupiter. They vary widely in shape and size. Some are almost completely round, while others look like chunks of rock. Ceres, with a diameter of 600 miles, is the largest asteroid. Most asteroids, however, are no bigger than boulders. These sometimes fall into Earth s atmosphere. When they do, they are called meteoroids. Meteoroids that strike the ground are called meteorites. Comets are made up of dust, different metallic ores, and ice. They have long oval orbits that take them very far from the sun. When a comet travels near the sun, the solar winds sweep its gases away from it, forming a tail. Sometimes, a second tail of dust is also visible. Asteroid Comet Hale-Bopp 14 15

10 Life on Other Planets One question has come up again and again about all of these objects traveling around the sun. Could there be life on any of them? Scientists have tried to answer this question for hundreds of years. There have been many different approaches to searching for life on other planets. For example, scientists have searched for planets that are a close version of Earth. So far, no planets have been found that would be hospitable enough for earthly life. Scientists explorations have taken them beyond our solar system to the vast universe. The universe is large, and it may be possible that alien life-forms exist. However, we cannot yet answer this question. To date there is no scientific proof that there is life on other planets. Throughout history, people have claimed to see aliens or their spacecraft here on Earth. None of these sightings has been proven true. Some people claim to have photographs or video recordings of alien spacecraft. Just like the eyewitness accounts, none provides positive evidence of aliens visiting Earth. From 1948 until the mid-1960s there were an increased number of flying saucer reports. Some people thought these reports were the result of spacecraft from the planet Mars, since scientists at the time believed that there was life on Mars. During this time, there were also many movies and science fiction novels about aliens invading Earth. This added to the idea that aliens existed and could come to our planet. The film Earth vs. the Flying Saucers (1956) showed scenes of aliens landing on Earth

11 X-ray images of the sun allow scientists to study its surface from far away. What s New in Space? Scientists are still exploring the mysteries of outer space. In October and November 2003, the sun erupted in powerful storms. Charged particles flew from the sun on solar winds. They hit Earth s atmosphere at amazing speeds for twenty days. When they struck Earth, the solar storms caused interruptions in satellite and radio signals. Pilots had to check their radio and navigation systems to be sure they were still working properly. At the time, American astronaut Mike Foale and Russian cosmonaut Alexander Kaleri were aboard the International Space Station. They had to take cover in the innermost part of the station in order to avoid the dangerous radiation from the solar winds. They also had to shut down some of their equipment so that it wasn t damaged. The storms puzzled scientists. Normally, these solar storms take a few days to reach Earth. But this time one of them took only nineteen hours. The storms were also unexpected because the sun was more active than normal. There was a lot for scientists to study

12 Future Space Travel There may come a day when anyone can travel to space. The scientists at NASA think that this day is not far away. They have developed a model of a futuristic space cruiseliner called Starship This exhibit has traveled throughout the country giving visitors a look at what space technology may be like forty years from now. Visitors to Starship 2040 learn about what space might be like in the future. They can listen to madeup conversations between the crew and their talking computers. They can explore the futuristic kitchen and learn about new technologies that NASA is working on. They can also learn about NASA s Vision for Space Exploration, which was announced in January of This is NASA s new project to expand their exploration of space. They are working on ways to send astronauts beyond the low orbits that they have taken in the past. NASA also hopes that the program will help humans better understand their universe. Starship 2040 provides a glimpse of a possible future where humans will travel and work in space as safely and affordably as we now fly on planes. Families can visit Starship

13 Humans and the Solar System Our solar system is a complex place that continues to capture our imaginations. We cannot refrain from wondering about it. There are still many puzzles to solve. We depend on scientists to help us find the answers. Astronomers, astronauts, and engineers all have major roles in our quest to discover the unknowns in the solar system, the galaxy, and the universe. These professionals work hard to gain a better understanding of planets, comets, asteroids, and moons. We are able to discover more about our solar system with technological advances in space stations, probes, and satellites, and through the skilled eyes of astronomers using highpowered telescopes. Would you like to study space from Earth or become an astronaut? Perhaps you would just like to be a passenger on one of the space cruisers of the future. Soon, it will all be up to you. 22 Astronomers study space from the Palomar Observatory. 23

14 Glossary Reader Response alien n. a creature or object from outer space. barge n. a large, strongly built vehicle or flat-bottomed boat. hospitable adj. friendly; receptive. molten adj. made liquid by heat; melted. ore n. a rock containing enough metal, or metals, to make mining profitable. refrain v. to keep yourself from doing something. universal adj. belonging to or concerning all; existing everywhere. version adj. one particular statement, account, or description. 1. Scientists are finding new ways to explore space all of the time. Based on what you have read, what do you think space exploration will be like in 40 years? 2. In order for life to exist on another planet, scientists believe that the planet would have to be very similar to Earth. Visualize what this planet may look like and what the other life-forms may be like. Write or draw a brief description of this planet. 3. Barge and refrain are both words that mean more than one thing. How are they used in this book? Look up the words in a dictionary and write another definition for each. Use a T-chart to write the new definitions below them. Barge Refrain 4. Look at the time line on pages 4 5. When did Sally Ride make her first flight into space? How long was that after Alan Shepard s first space flight? Why do you think it took so long for an American woman to go into space? 24