Space and Technology Genre Comprehension Skill Text Features Science Content Nonfi ction Predict • Captions Solar System • Call Outs • Text Boxes • Glossary Scott Foresman Science 4.18 ISBN 0-328-13910-6 ì<(sk$m)=bdjbab< +^-Ä-U-Ä-U by Kimberly Taylor 13910_CVR_FSD Cover1 5/26/2005 11:06:51 AM Vocabulary What did you learn? astronomy 1. WhatInner are some and differences Outer between innerPlanets and outer planets? craters by Kimberly Taylor galaxy 2. How were Mercury’s craters made? satellite 3. Why will astronauts’ footprints remain on the Moon’s surface for years? solar system 4. Neptune was discovered in space probe 1846. On your own paper, describe how scientists universe discovered this planet. Include details from the book to support your answer. 5. Predict Do you think more moons of Jupiter will be discovered? Why or why not? Photographs: 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: ©Stocktrek/Corbis; Title Page: ©Mark Garlick/Photo Researchers, Inc.; 6 ©USGS/Photo Researchers, Inc.; 7 JPL/NASA; 8 Getty Images; 9 Getty Images; 10 JSC/NASA; 11 U.S. Geological Survey; 12 JPL/NASA; 13 (BL, R) NASA, (CR) Getty Images, (BR) JPL/NASA; 14 JPL/NASA; 15 ©Calvin Hamilton Solar Views; 16 (TL, BL) ©Mark Garlick/Photo Researchers, Inc.; 17 ©Mark Garlick/Photo Researchers, Inc.; 18 JPL/NASA; 19 ©Mark Garlick/Photo Researchers, Inc.; 20 NASA; 22 (BL) ©Mark Garlick/Photo Researchers, Inc. ISBN: 0-328-13910-6 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 permissions, write to: Permissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025. 3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06 05 13910_CVR_FSD Sec1:2 13910_01-24_FSD 1 5/26/20055/26/05 11:07:064:15:48 PM AM Astronomy is the study of the stars, the Sun, the Moon, and What makes up the universe? other objects in space. People have always been interested in objects in the sky. Experts think that the ancient Egyptians built The Universe and the Milky Way the Great Pyramids to line up with the stars. The universe includes all of space and everything in it. Other groups of people also studied astronomy long ago. Most of the universe is empty space. Arabs, Chinese, Indians, Greeks, and others used astronomy A galaxy is a system of gases, dust, and billions of stars to figure out the right time for planting or harvesting crops. clustered together. The universe has millions of galaxies. We Sailors used the Sun and the stars to find their way on the live in the Milky Way galaxy. The Milky Way has a flat spiral open sea. shape. There are billions of stars in the Milky Way. The Sun is one of these stars. It is near the edge of our galaxy. 2 3 13910_01-24_FSD 2 5/26/05 4:16:05 PM 13910_01-24_FSD 3 5/26/05 4:16:10 PM Our Solar System The Sun The solar system includes the planets, their moons, the The Sun is the largest object in our solar system. It is a Sun, and other objects. All objects in the solar system revolve medium-sized star. The Sun is a huge ball of glowing, hot gases. around, or orbit, the Sun. A planet is a large, ball-shaped object The inner parts of the Sun are much hotter than the outer parts. that moves around a star such as the Sun. A planet is smaller Energy from the Sun gives heat and light to Earth. and cooler than a star. The Sun has magnetism, just as Earth does. The magnetic The planets closest to the Sun are Mercury, Venus, Earth, and field around some parts of the Sun can be very strong. Hot gas Mars. They are the inner planets. The outer planets are Jupiter, can burst from the surface of the Sun and form loops in these Saturn, Uranus, Neptune, and Pluto. An area with many areas. Sunspots are dark spots on the Sun. They appear at very asteroids is between the inner and outer planets. Asteroids are strong parts of the magnetic field. rocky objects that are too small to be called planets. The Sun’s gravity keeps Earth and other space objects in their orbits. The orbits of the inner planets are shaped like circles. The orbits of the outer planets are more like ovals. The sizes and distances in this diagram are not true to scale. Also, the planets rarely line up. Asteroid belt Jupiter Pluto Earth Venus Sun Uranus Neptune Mercury Mars Saturn 4 5 13910_01-24_FSD 4 5/26/05 4:16:14 PM 13910_01-24_FSD 5 5/26/05 4:16:22 PM Venus What are the inner planets? Venus is about the same size as Earth. It is the second planet Mercury from the Sun. Venus is very dry and hot, just as Mercury is. However, Venus has an atmosphere. This atmosphere is made Mercury is the planet closest to the Sun. It has thousands of of thick, swirling clouds. These clouds dents called craters. They were formed by meteorites crashing are very hot and poisonous. into Mercury’s surface. A meteorite is a rock from space that Venus has strong winds hits a planet. and a lot of lightning. Its A space probe is a vehicle that uses cameras and other clouds reflect sunlight tools to study different objects in space. In 1974 the Mariner 10 well. At night Venus is space probe was sent to Mercury. one of the brightest Too Hot and Too Cold objects we see in the sky. There is almost no atmosphere on Mercury. It is very hot during the day. Without an atmosphere to hold heat, Mercury is very cold at night. Mercury Facts Venus Facts Distance from Sun Distance from Sun 57,900,000 km (35,983,000 mi) 108,200,000 km (67,200,000 mi) Diameter Diameter 4,879 km (3,032 mi) 12,104 km (7,521 mi) Length of day as measured in Earth time Length of day as measured in Earth time 59 days 243 days (spins backward) Length of year as measured in Earth time Length of year as measured in Earth time 88 days 225 days Average surface temperature Average surface temperature 117°C (332°F) 464°C (867°F) Moons Moons none none Weight of a person who is 100 lb on Earth Weight of a person who is 100 lb on Earth 38 lb 91 lb 6 77 13910_01-24_FSD 6 5/26/05 4:16:24 PM 13910_01-24_FSD 7 5/26/05 4:16:28 PM Earth The Moon Earth is the largest rocky planet in the solar system. It is the A satellite is an object that orbits another object in space. third planet from the Sun. It is the only planet whose surface Moons are satellites of planets. They revolve around planets has liquid water. In fact, water covers most of its surface. just as planets revolve around the Sun. A moon stays in orbit Earth is surrounded by a layer of gas called the atmosphere. around a planet because of the force of gravity between the The atmosphere makes life possible. It keeps some of the Sun’s moon and the planet. harmful rays from reaching Earth. The atmosphere is mostly Earth has one moon. Earth is about four times the size of nitrogen, water vapor, carbon dioxide, and oxygen. Animals its moon. The Moon has no atmosphere. It has many craters and plants use these gases. Earth is the only planet in caused by meteorites. the solar system known to have life on it. Earth Facts Distance from Sun 149,600,000 km (93,000,000 mi) Diameter 12,756 km (7,926 mi) Length of day as measured in Earth time 24 hours Length of year as measured in Earth time 365 days Average surface temperature 15ºC (59ºF) Moons 1 Weight of a person who is 100 lb on Earth 100 lb 8 9 13910_01-24_FSD 8 5/26/05 4:16:33 PM 13910_01-24_FSD 9 5/26/05 4:16:36 PM Exploring the Moon Mars Sputnik was the first artificial satellite. It was launched in Mars is the fourth planet from the Sun. It is covered by rocks 1957 by the former Soviet Union. In 1959, the Soviet Union and soil that are made of the mineral iron oxide. Iron oxide sent the first probes to the Moon. No people were on these is reddish brown. Because of this, Mars is nicknamed the “Red probes. Planet.” Mars has two moons with deep craters. Phobos, one of The first person to travel in space was Russian cosmonaut its moons, is very close to Mars. Yuri Gagarin. In 1961, he circled Earth in less than two Winds on Mars cause dust storms that are large enough hours in the spaceship Vostok I. The first people to step on to cover the entire planet.