The Solar System. Lesson 3

Transcription

1 Lesson 3 The Solar System Stonehenge, England How many planets do you see? Mars, Saturn, and Venus are in a triangle above the center stone. Mercury is below them to the left. Jupiter is much higher to the right. How far away are these planets from Earth? 434 ENGAGE ESS.42 Differentiate among moons, asteroids, comets, meteoroids, meteors, and meteorites (ESS-M-C2) ESS.43 Describe the characteristics of the inner and outer planets (ESS-M-C2) ESS.45 Identify Earth s position in the solar system (ESS-M-C5)

2 How far apart are the planets? Materials Purpose Make a model that shows the distances between the planets using astronomical units (AU), where one AU equals the average distance between Earth and the Sun. This distance is about 149,591,000 km (92,960,000 mi). Procedure Let the length of each paper towel equal 1 AU. Using the information on the chart, roll out the number of paper towels you need to show the distance from the Sun to Neptune. Make a Model Mark the location of the Sun at one end. Measure the distance that each planet would be from the Sun and draw the planet on the paper towel. Draw Conclusions Interpret Data Compare the distances between Mercury and Mars, Mars and Jupiter, and Jupiter and Neptune. Which are farthest apart? Infer What can you conclude about the distances between the planets in the solar system? paper towels markers ruler masking tape Step Distances of the Planets from the Sun Planet Distance in AU Mercury 0.4 Venus 0.7 Earth 1 Mars 1.5 Jupiter 5.2 Saturn 9.5 Uranus 19.2 Neptune 30 Explore More Your model has all of the planets in a line. How could you make a model to show the positions of the planets at a specific time? Write instructions that others can follow to make the model. Step SI.12 Use data and information gathered to develop an explanation of experimental results (SI-M-A4) SI.14 Develop models to illustrate or explain conclusions reached through investigation (SI-M-A5) Also covers SI EXPLORE

3 Essential Question What are the components of our solar system? ESS.42, ESS.43, ESS.45 Vocabulary planet, p. 436 solar system, p. 436 inner planet, p. 438 outer planet, p. 440 comet, p. 442 asteroid, p. 443 meteor, p. 443 moon, p. 444 Reading Skill Infer Clues What I Know What I Infer Technology e-glossary and e-review online at Earth is the third planet from the Sun. What is the solar system? In ancient times, observers noticed that the stars stayed the same distance from one another as they moved across the night sky. However, they noticed a few exceptions. Five of the tiny bright lights appeared in different parts of the sky every night. They did not stay the same distance from the other stars. At other times they were not present at all. The ancient Greek observers named these objects planets, a word that means wanderer. A planet is a large object that orbits a star. Many ancient observers believed that Earth was the center of everything. They believed the Sun and all the objects in the night sky revolved around Earth in perfect circles. However, many astronomers doubted this belief because the planets moved in different ways. In the early 1500s, the mathematician and astronomer Nicolaus Copernicus argued that Earth rotated on its axis and revolved around the Sun. His view changed how later astronomers understood the stars and planets. Earth is one of eight planets in our solar system. A solar system is a star and the objects that orbit it. The eight planets in our solar system revolve around the Sun in elliptical orbits. Their order from nearest to farthest from the Sun is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Quick Check Infer If scientists discovered a large object moving around a distant star, what would they call it? Critical Thinking Is a moon that is larger than many of the planets in a solar system also a planet? Explain your answer. 436

4 The Solar System Venus Sun Mercury Mars Earth asteroid belt Jupiter Uranus Saturn Planetary Data Planet Name Radius at the Equator (km) Mean Surface Temperature ( C) Surface Materials Rings Mercury 2, rocks no Venus 6, rocks no Earth 6, rocks no Mars 3, rocks no Jupiter 71, gases yes Saturn 60, gases yes Neptune Uranus 25, gases yes Neptune 24, to -153 gases yes Read a Table Which planet has the warmest surface temperature? Clue: Find the highest temperature in the mean surface temperature column. 437

5 What are the inner planets? The inner planets are closer to the Sun than the asteroid belt. These planets are Mercury, Venus, Earth, and Mars. Although each inner planet has unique features, the inner planets have common characteristics. For example, the inner planets all have surfaces made of rock. Because of these rocky surfaces, the inner planets are also called the terrestrial planets. The inner planets orbits are also spaced close together. These planets have few or no moons, and none of them have rings. Venus Mercury Distance From the Sun: 58 million km (36 million mi) Mass: 0.06 Earth Surface Gravity: 0.38 Earth Number of Moons: 0 Surface Characteristics: Mercury s surface looks a lot like the Moon s surface. It is heavily scarred with craters. These craters were formed when meteorites smashed into the planet s surface. Special Features: Mercury has no true atmosphere. Because Mercury does not have an atmosphere, daytime temperatures are extremely high and nighttime temperatures are extremely low. Distance From the Sun: 108 million km (67 million mi) Mass: 0.82 Earth Surface Gravity: 0.91 Earth Number of Moons: 0 Surface Characteristics: The surface of Venus shows evidence of violent volcanic activity in the past. Venus has shield and composite volcanoes similar to those found on Earth. Long rivers of lava have been seen on Venus. Special Features: A day on Venus is longer than its year. Venus rotates once every 243 Earth days and revolves around the Sun in 225 Earth days. Venus also rotates in the direction opposite Earth s rotation. Pressure at the surface of Venus is about 90 times the atmospheric pressure at Earth s surface. This pressure is enough to crush a spacecraft. The sizes of Mercury, Venus, and Mars are shown compared to Earth. 438

6 Distance From the Sun: 150 million km (93 million mi) Mass: 1 Earth Number of Moons: 1 Earth Surface Characteristics: There might once have been as many craters on Earth as there are on Mercury. However, erosion on Earth caused these craters to disappear. Special Features: Earth is the largest inner planet. It is the only planet in the solar system known to support life as we know it. Earth s atmosphere keeps it from getting too hot or too cold. Planet Sizes SI.14, SI.15 Use Numbers Using a scale of 2,000 km = 1 cm, find the diameter of each planet in centimeters. Make a Model Using a ruler and scissors, cut circles out of poster board to show the sizes of the planets. Then label each planet. Arrange the planets in order from nearest to farthest from the Sun. How do the sizes of the inner and outer planets compare? Which planet is about the same size as Earth? Mars Distance From the Sun: million km (141.6 million mi) Mass: 0.11 Earth Surface Gravity: 0.38 Earth Number of Moons: 2 Surface Characteristics: Mars is known as the red planet because it has a reddish surface color. Special Features: Mars s axis is tilted 25. This means it has seasons. Polar ice caps melt in summer and form in winter. Quick Check Infer If you were on Venus, in what direction would you see the Sun rise and set? Explain. Critical Thinking How are the inner planets alike? How are they different? 439

7 What are the outer planets? There are four planets beyond the asteroid belt. These planets are known as the outer planets. The outer planets include Jupiter, Saturn, Uranus, and Neptune. Although they differ from each other, these planets have some similarities. The outer planets are made mostly of gas. They are sometimes called the gas planets. Each of the gas planets has a metallic core and a thick atmosphere. They are much larger than the inner planets. Their orbits are also much farther apart than the orbits of the inner planets. All the outer planets have rings and many moons. A day on an outer planet is very short; they spin rapidly on their axes. Jupiter Distance From the Sun: 778 million km (483 million mi) Mass: 318 Earth Surface Gravity: 2.53 Earth Number of Moons: 60+ Atmosphere Characteristics: The Great Red Spot is a huge storm that has been blowing continuously for more than 400 years. Its winds can reach speeds of about 435 km/h (270 mph). The storm is large enough to hold several Earths. Scientists believe that a combination of sulfur and phosphorus in the atmosphere gives this storm its color. Special Features: Jupiter is so large that 1,000 Earths could fit inside it. It also has more mass than all of the other planets combined. Jupiter rotates faster than any other planet. It takes only 9 hours and 56 minutes to rotate once on its axis. Saturn 440 Distance From the Sun: 1,427 million km (886.7 million mi) Mass: 95 Earth Surface Gravity: 1.07 Earth Number of Moons: 60+ Atmosphere Characteristics: Saturn s atmosphere is similar to Jupiter s. It is composed mostly of hydrogen and helium. Winds on Saturn move at about 1,800 km/h (1,100 mph) near the equator. Special Features: Saturn is known for its large, bright rings. The rings are made of pieces of ice and rock.

8 Uranus Distance From the Sun: 2,870 million km (1,783 million mi) Mass: 14.5 Earth Surface Gravity: 0.90 Earth Number of Moons: 20+ Atmosphere Characteristics: The bluegreen color of Uranus is due to methane in the planet s upper atmosphere. Special Features: Uranus is unusual because it looks as though it was knocked on its side. Its axis of rotation is tilted about 98 to its orbit. Scientists think that a collision with another object caused Uranus to tip on its side. The sizes of Saturn, Uranus, and Neptune are shown compared to Jupiter. Neptune Distance From the Sun: 4,500 million km (2,796 million mi) Mass: 17.2 Earth Surface Gravity: 1.14 Earth Number of Moons: 13 Atmosphere Characteristics: Like Uranus, methane in its atmosphere gives Neptune its blue color. Neptune has the strongest winds of any planet. The winds were measured to blow at speeds up to 2,000 km/h (1,250 mph) in some areas. Many storms have been detected. Special Features: Neptune has at least five rings, none of which are very bright. One of Neptune s moons, Triton, is larger than Pluto. Dwarf Planets Pluto was once known as the ninth planet. Pluto s elongated orbit and small size are different from those of the other planets. Because of these differences, scientists debated whether Pluto should be classified as a planet. In August 2006, the International Astronomical Union officially reclassified Pluto as a dwarf planet. Other dwarf planets include Ceres and Eris. Ceres is found in the asteroid belt between Mars and Jupiter. Eris is slightly larger than Pluto and even farther from the Sun. Quick Check Infer If scientists discover a new planet that appears to be the same color as Uranus, what can you infer about its atmosphere? Critical Thinking Why might the outer planets have so many more moons than the inner planets? 441

9 What are asteroids, comets, and meteors? Different types of small objects are present in space. These objects include comets, asteroids, and meteors. Comets A comet is a mixture of frozen gases, ice, dust, and rock that moves in an elliptical orbit around the Sun. Comets are thought to be bits of material left over from the formation of the solar system about 4.6 billion years ago. When a comet is farther away from the Sun, the gases and ice in the comet are frozen. As the comet moves toward the Sun, the core, or nucleus, of the comet warms up. Some of the ice and the dust in the core form a cloud, or coma, around the nucleus. Together, the nucleus and the coma make up the head of the comet. As the comet gets closer to the Sun, heat from the Sun pushes some of the coma away from the comet. This material forms a glowing tail that may stretch millions of kilometers behind the head. Sometimes two tails will form. One tail is made of ice, and one is made of gases. Heat energy moves out from the Sun in every direction. As a comet moves around the Sun, the head stays closest to the Sun and the tail trails out behind it. No matter where the comet is in its path around the Sun, the comet s tail always points away from the Sun. Comets orbit the Sun, but the amount of time it takes them to orbit the Sun varies. Halley s Comet was the first comet whose return was predicted. The comet gets close to Earth about every 76 years, most recently in The next time Halley s Comet will be near Earth is in Comets have tails of ice and gases. 442

10 The Leonid meteor shower occurs every year in mid-november. Asteroids An asteroid (AS tuh royd) is a rock that revolves around the Sun. Most of the thousands of asteroids in the solar system are located between Mars and Jupiter in the asteroid belt. Many asteroids have irregular shapes and look like potatoes. Some asteroids are less than 2 km (1 mi) wide, while others can be up to 800 km (500 mi) wide! Meteors The solar system is full of other small objects. In space, these objects are called meteoroids. If an object crosses paths with Earth and enters Earth s atmosphere, it is called a meteor. Most meteors burn up as they travel through Earth s atmosphere. If a meteor does land on the ground, it is called a meteorite. Ida is a heavily cratered, irregularly shaped asteroid. Quick Check Infer As scientists identify materials in comets, what might they infer about the materials that existed as the solar system formed? Critical Thinking Draw the location of the tail and the head of a comet as it moves around the Sun. 443

11 Various Moons of the Solar System Ganymede (Jupiter) Moon (Earth) Deimos (Mars) Phobos (Mars) SCALE 1 cm 1,000 km SCALE 1 cm 10 km How do the moons compare? A moon is a natural object that orbits a planet. Different planets have different numbers and sizes of moons. The inner planets have fewer moons than the outer planets. Mercury and Venus do not have moons. Earth has one moon, and Mars has two. With more than 60 moons, Jupiter has the most moons of any planet in the solar system. Saturn has more than 45 moons. Astronomers have discovered at least 27 moons around Uranus and 13 moons orbiting Neptune. As astronomers observe the outer planets with better telescopes and with space probes, they continue to find more moons. Moons are also called satellites (SA tuh lites). A satellite is an object in space that circles around another object. While moons are natural satellites, people also put objects into space that orbit Earth or other planets. These objects are called artificial satellites. They include weather and communications satellites as well as space probes that orbit planets to observe their surfaces. The size of the moons in the solar system varies. Some of the moons are only a few kilometers wide. Jupiter s Ganymede is the largest moon in the solar system. Ganymede is larger in diameter than Pluto and Mercury. Earth s moon is also larger than Pluto and is visible without a telescope. Ganymede is the only other moon that can be seen without a telescope. 444

12 Mimas (Saturn) Hyperion (Saturn) Miranda (Uranus) SCALE 1 cm 100 km Read a Photo How large are these moons? Clue: Use the scales. Forming Craters Sometimes small objects in space collide with large objects. When this happens, the impact often forms a crater, or a bowl-shaped hole, on the larger object s surface. Many moons have craters. Craters vary in size because the objects that hit a moon are different sizes and travel at different speeds. On Earth s moon, the impact of an object knocks the surface material away so the rock underneath is exposed. The surface material piles around the edges of the crater. This makes the Moon s craters distinct and easy to see from Earth. Ganymede s surface is made of ice and rock. The dark rock is about 4 billion years old and the lightcolored rock is somewhat younger. Craters are seen on both types of rock. This means that objects have been hitting Ganymede for at least 4 billion years. Unlike those on the Moon, craters on Ganymede are flat. This may be because flowing ice on Ganymede s surface smooths out their edges. Deimos, Mars s smaller moon, is composed of carbon-rich rock and ice. Deimos s surface has craters that have been partially filled in by loose rock. Quick Check Infer How are a moon and an artificial satellite different? Critical Thinking What happens when objects in space collide with Earth? 445

13 What is Earth s moon like? The Moon has been a source of wonder throughout history. As technology has progressed, people have wanted to learn more and more about the Moon. The greatest amount of information about the Moon has come from data gathered by the Apollo missions, which included six Moon landings between 1969 and Several different features have been identified on the Moon. Even though the Moon and Earth are hit by space objects at about the same rate, the Moon has more craters. Earth s protective atmosphere causes most of the incoming objects to burn up. Maria (MAR ee uh) are large, dark, flat surfaces on the Moon. The singular form, mare (MAR ay), means sea in Latin. The smoothness of the maria led people long ago to think that they might be seas of water. Today scientists think the maria formed when huge space objects collided with the Moon s surface. These large areas of impact then filled in with lava. When the lava cooled, it gave the maria their smooth appearance and dark color. Highlands on the Moon are lightcolored regions near the lunar poles. They are higher in elevation compared to the maria. The surfaces of the highlands have more craters than the maria do, so scientists believe that the highlands are geologically older landforms. Mountains on the Moon are found around the edges of large maria. The mountains probably formed from the same impacts that formed the maria. Mountain ranges on the Moon are named after mountain ranges on Earth. Valleys on the Moon are cigarshaped depressions. Perhaps the most famous is the Alpine Valley on the northeastern edge of Mare Imbrium. New evidence suggest that the floors of some deep Moon valleys may contain small amounts of ice. Quick Check Infer What probably caused mountains to form around the edges of the maria? Critical Thinking Why do people who go to the Moon need to wear space suits? Mount Hadley Delta rises about 4,000 m (13, 124 ft). This image shows craters on the Moon s surface and a view of Earth in the background. 446

14 Visual Summary The solar system is made of the Sun, the planets and their moons, asteroids, meteoroids, and comets. The planets and moons in the solar system vary in size and surface material. Think, Talk, and Write Vocabulary A mixture of frozen gases, ice, dust, and rock that orbits the Sun is a(n). Infer If you knew probes that traveled to Venus were crushed after a few hours, what could you infer about atmospheric pressure on Venus? Clues What I Know What I Infer Make a Study Guide Make a three-tab book. Use the titles shown. On the inside of each tab, summarize what you have learned. The Moon has a surface of different features, including craters, maria, and highlands. Critical Thinking Earth is the only planet known to have life. What do you think makes this possible? What might prevent life from existing on other planets? Test Prep Which is the largest planet in the solar system? A Earth B Mars C Saturn D Jupiter Test Prep Which planet takes the longest time to orbit the Sun? A Mercury B Venus C Jupiter D Uranus Essential Question What are the components of our solar system? Writing Link Science Fiction Read The War of the Worlds by H.G. Wells. Write a report about the novel. Discuss how much of the story is based on fact and how much is fiction. Art Link Planet Surfaces Research the surface features of one of the inner planets. Then draw an illustration of what the planet s surface might look like. -Review Summaries and quizzes online at EVALUATE

15 Materials construction paper Structured Inquiry How can you model the solar system? Purpose Our solar system consists of the Sun, planets, moons, and other bodies, including asteroids, comets, and meteoroids. Each planet has its own orbit around the Sun. What can a model of the solar system show you? Construct a model of the solar system and use it to compare the distances between planets. markers dowels tape 30-m tape measure Procedure Make a Model Make labels for each planet and the Sun. Attach each label to a dowel. Place the marker labeled Sun at one end of a large open area. Measure Use the table below to construct your model. Measure the scaled distance from the Sun to Mercury, and place the marker labeled Mercury in the ground. Continue marking the distances of the planets from the Sun. Draw your model and record your observations about the solar system. Step Step Planet Distance from Sun (in kilometers) Distance from Sun, to Scale (1 cm = 1,000,000 km) Mercury 57,900, cm Venus 108,200,000 1 m, 8 cm Earth 149,600,000 1 m, 50 cm Mars 227,900,000 2 m, 28 cm Jupiter 778,400,000 7 m, 78 cm Saturn 1,426,700, m, 27 cm Uranus 2,871,000, m, 71 cm Neptune 4,498,300, m, 98 cm Step 448 EXTEND

16 Draw Conclusions Interpret Data According to your model, which planet is closest to the Sun? Which planet is closest to Earth? Interpret Data How does the distance from the Sun to Jupiter compare to the distance from Jupiter to Saturn? How does the distance from the Sun to Saturn compare to the distance from Saturn to Uranus? Guided Inquiry Could you model the solar system, including the planets sizes and the distances between the planets? Form a Hypothesis Why is it so difficult to make a true scale model of the solar system? Write your answer in the form If I try to model the sizes of the Sun and all the planets accurately, then... Test Your Hypothesis Decide what data you need to collect to make your model. Then choose a scale to use for your model, and calculate the sizes and positions of your model Sun and planets. Draw Conclusions How easy would it be to make your model? Explain. Open Inquiry Think of a question about the solar system to investigate. For example, are the planets always the same distance from the Sun, or do their distances change? Design a data-collection process or method of research to answer your question. Your data must be organized to test only one variable, or one item being changed. Remember to follow the steps of the scientific process. Ask a Question Form a Hypothesis Test Your Hypothesis Draw Conclusions SI.33 Evaluate models, identify problems in design, and make recommendations for improvement (SI-M-B4) SI.38 Explain that, through the use of scientific processes and knowledge, people can solve problems, make decisions, and form new ideas (SI-M-B6) Also covers SI.14, SI EXTEND