Lesson 1 The View from Earth

Transcription

1 Lesson 1 The View from Earth Student Labs and Activities Page Launch Lab 8 Content Vocabulary 9 Lesson Outline 10 MiniLab 12 Content Practice A 13 Content Practice B 14 Math Skills 15 School to Home 16 Key Concept Builders 17 Enrichment 21 Challenge 22 Skill Practice 23 Stars and Galaxies 7

2 Launch Lab LESSON 1: 20 minutes How can you see invisible energy? You see because of the Sun s light. You feel the heat of the Sun s energy. The Sun produces other kinds of energy that you can t directly see or feel. Procedure 1. Read and complete a lab safety form. 2. Put 5 6 beads into a clear container. Observe the color of the beads. 3. In a darkened room, shine light from a flashlight onto the beads for several seconds. Record your observations in the Data and Observations section below. Repeat this step, exposing the beads to light from an incandescent lightbulb and a fluorescent light. Record your observations. 4. Stand outside in a shady spot for several seconds. Then expose the beads to direct sunlight. Record your observations. Data and Observations Think About This 1. How did the light from the different light sources affect the color of the beads? 2. What do you think made the beads change color? 3. Key Concept How do you think invisible forms of light help scientists understand stars and other objects in the sky? 8 Stars and Galaxies

3 Content Vocabulary LESSON 1 The View from Earth Directions: Explain the relationship between the terms in each pair on the lines provided. Use complete sentences. 1. astronomical unit; light-year 2. apparent magnitude; luminosity 3. parallax; apparent 4. spectroscope; electromagnetic spectrum Stars and Galaxies 9

4 Lesson Outline LESSON 1 The View from Earth A. Looking at the Night Sky 1. Because Earth rotates from west to east, objects in the sky rise in the and set in the. 2. Stars near never set when viewed from the hemisphere. 3. When you look at the sky with just your eyes and you do not use binoculars or a telescope, you are experiencing astronomy. 4. Patterns that people thousands of years ago identified in the night sky are called ancient. 5. collect more light than people can detect with their alone. a. Telescopes can also detect a range of from the electromagnetic spectrum, not just visible. b. A star emits a range of wavelengths, which is called the star s. 6. To study the spectra of stars, scientists use an instrument called a(n), which spreads light into different wavelengths. a. Young stars give off mainly low-energy wavelengths, including waves and waves. b. Exploding stars emit mainly high-energy waves and. B. Measuring Distances 1. The apparent change in an object s position that occurs when you look at the object from two different points is called. 2. Within the solar system, astronomers measure distances using the unit, which is defined as the average distance between and. 10 Stars and Galaxies

5 Lesson Outline continued 3. Outside the solar system, scientists measure distances in a unit called a(n), which is the distance light travels in Because it takes for light to travel, when you look at a star, you see the star not as it is today but as it was when the left the star. C. Measuring Brightness 1. Scientists measure a star s in two ways: how bright the star seems to be when it is viewed from the star actually is. 2. An ancient Greek astronomer named Hipparchus used to rate the stars according to how bright they looked in the night sky. and how bright a. Today astronomers call Hipparchus s numbers. b. The measure of how bright an object appears from Earth is called the of the object. c. Almost all the brightest stars have an apparent magnitude of. 3. Stars appear to be bright or dim depending on their from Earth, but stars have an actual, or, magnitude. a. The true brightness of an object is called its. b. A star s luminosity depends on the star s and but not its distance from. Stars and Galaxies 11

6 MiniLab LESSON 1: 20 minutes How does light differ? Light from the Sun is different from light from a lightbulb. How do the light sources differ? Procedure 1. Read and complete a lab safety form. 2. Follow instructions included with your spectroscope. Use it to observe various light sources around the classroom. Then use it to look at a bright part of the sky. Do not look directly at the Sun. 3. Use colored pencils to draw what you see for each type of light in the Data and Observations section below. Data and Observations Analyze and Conclude 1. Compare and Contrast What colors did you see for each light source? How did the colors differ? 2. Key Concept How might a spectroscope be used to learn about stars? 12 Stars and Galaxies

7 Content Practice A LESSON 1 The View from Earth Directions: Circle the term in parentheses that correctly completes each sentence. 1. Because Earth rotates on its axis from west to east, the stars and planets in the sky appear (to move, brighter) during the course of the night. 2. The North Star, named (Sirius, Polaris), is almost directly above the North Pole. 3. The stars in a (galaxy, constellation) happen to appear close together when they are seen from Earth, but they are far apart in space. 4. Astronomers divide the sky into 88 (regions, solar systems), also called constellations. 5. A star emits a range of (magnitudes, wavelengths) called its spectrum. 6. Telescopes can detect visible light and other types of (radiation, wavelengths). 7. A spectroscope spreads light into different (elements, wavelengths). 8. Astronomers can analyze the elements that make up a star by passing its light through a (spectroscope, telescope). 9. Different types of (planets, stars) emit electromagnetic radiation with different wavelengths. 10. A stationary object might appear to change (luminosity, position) when it is viewed from two different points. 11. (Parallax, Luminosity) is the apparent change in an object s position caused by looking at it from two different points. 12. Astronomical units are convenient to use in the solar system because distances easily can be compared to the distance between Earth and the (Sun, Moon). 13. Light-years measure distances to objects that are (outside, within) the solar system. 14. The brightness of an object as seen from Earth is its (absolute, apparent) magnitude. 15. (Luminosity, Parallax) is the true brightness of an object. Stars and Galaxies 13

8 Content Practice B LESSON 1 The View from Earth Directions: On each line, write the term or phrase that correctly completes each sentence. Looking at the Night Sky 1. Astronomers divide the night sky into. 2. Telescopes and spectroscopes are used to. Measuring Distances 3. Astronomers use astronomical units to. 4. Light-years are used to measure. Measuring Brightness 5. The apparent magnitude of an object is a measure of 6. The luminosity of a star depends on.. 14 Stars and Galaxies

9 Math Skills LESSON 1 Use Proportions A rate is a ratio of two units. For instance, a car that travels 65 miles in 1 hour is moving at 65 mi a rate of 65 mi/hr or 1 hr. Two equal ratios can be written as a proportion. If one of the numbers in a proportion is unknown, you can cross multiply to solve for the unknown number, x. When writing a proportion, make sure you put the numbers in the correct places. The numerators of the ratios should have the same units, and the denominators of the ratios should have the other units. If light travels around 10 trillion km in 1 year, how long would it take light to reach Earth from a star that is 280 trillion km away? Step 1 Use the information in the problem to write a proportion. The numerator of each fraction has kilometers as units, so the proportion is written correctly as 10 trillion km = 1 y Step 2 Cross multiply. 280 trillion km x. 10 trillion km (x) = 280 trillion km y Step 3 Solve for x by dividing both sides. Practice 10 trillion km (x) 10 trillion km = 280 trillion km y 10 trillion km x = 28 y 1. If light travels around 10 trillion km in 1 year, how long would it take light to reach Earth from a star that is 390 trillion km away? 2. The star Proxima Centauri is 4.2 light-years away from Earth. How many kilometers separate this star from Earth? 3. An astronomical unit (AU) is about 150 million km. If Jupiter is 5.2 AU from the Sun, then how many kilometers away from Jupiter is the Sun? 4. If light travels about 300,000 km/s and Earth is about 150,000,000 km from the Sun, how many seconds does it take light from the Sun to reach Earth? Stars and Galaxies 15

10 School to Home LESSON 1 The View from Earth In this activity, you will investigate how distance affects brightness. You will need two flashlights (one large and one small), a darkened room, and a learning partner. Note: The lightbulbs in your flashlights should be the same type high intensity or incandescent. 1. With your partner, place the large flashlight on the floor at one end of a large room. The flashlight should be perpendicular to the wall so it shines into the room. Turn the flashlight on. 2. Place the small flashlight on the floor in the center of the room. Make sure this flashlight is pointing in the same direction as the large flashlight. Turn the flashlight on. 3. Darken the room and observe the flashlights. Be careful as you move around the darkened room. 4. Your partner and you should view both flashlights head on. Explain which light is brighter and why. 5. Now work with your partner to vary the distances of the flashlights from your observation spot so both appear equally bright. 6. Explain why both flashlights look equally bright, although one is actually brighter than the other. 7. Discuss your observations with your partner. Explain the outcome of step 5 in terms of absolute and apparent magnitude. 16 Stars and Galaxies

11 Key Concept Builder LESSON 1 The View from Earth Key Concept How do astronomers divide the night sky? Directions: Answer each question in the space provided. Question Answer 1. Before the invention of the telescope, how did people learn about planets and astronomical events? 2. Why did people observe stars during the 1600s? 3. What did people in ancient cultures see in the night sky? 4. What figure did people from ancient cultures see in the constellation Orion? 5. How did the Greek astronomer Ptolemy divide the night sky? 6. How do astronomers today use ancient constellations? 7. How does dividing the sky help astronomers today? Stars and Galaxies 17

12 Key Concept Builder LESSON 1 The View from Earth Key Concept What can astronomers learn about stars from their light? Directions: On each line, write the term from the word bank that correctly completes each sentence. Some terms may by used more than once or not at all. Use the diagram to answer questions 8 and 9. Low energy Long wavelength Electromagnetic Spectrum High energy Short wavelength Radiation Type Radio Microwave Infrared Visible Ultraviolet X-ray Gamma ray Wavelength (m) constellation electromagnetic high-energy low-energy spectroscope spectrum telescope wavelength 1. Different objects in space emit different ranges of wavelengths from the spectrum. 2. The range of wavelengths that a star emits is the star s. 3. Visible light is just a small part of the spectrum. 4. A star emits light that is characteristic of its makeup. A(n) measures the properties of light with specific wavelengths. 5. An optical uses mirrors or lenses to collect electromagnetic radiation emitted by stars. 6. Some stars emit radio waves that can be collected by a(n) and analyzed with a spectroscope. 7. Astronomers can study the temperature, composition, and energy of a star using a(n). 8. An exploding star emits mostly ultraviolet waves and X-rays. 9. A newly formed star emits mostly radio and infrared rays. 18 Stars and Galaxies

13 Key Concept Builder LESSON 1 The View from Earth Key Concept How do scientists measure the distance and the brightness of objects in the sky? Directions: On the line before each statement, write T if the statement is true or F if the statement is false. If the statement is false, change the underlined word(s) to make it true. Write your changes on the lines provided. 1. Spectroscope is the apparent change in an object s position caused by looking at it from two different points. 2. Astronomers use parallax to measure how far some objects are from Earth. 3. Astronomical units describe distance outside the solar system. 4. One AU is the average distance from Earth to the Moon. 5. Mercury and Venus are less than 1 AU from the Sun. 6. Mars and Jupiter are more than 1 AU from the Sun. 7. One light-year is the distance the Sun travels in 1 year. 8. A light-year measures time. 9. The nearest star to the Sun is about 4.2 kilometers away. 10. It would take 10 years for light to reach Earth from a star that is 100 trillion km away. 11. The distant stars you see today appear as they will be in the future. Stars and Galaxies 19

14 Key Concept Builder LESSON 1 The View from Earth Key Concept How do scientists measure the distance and the brightness of objects in the sky? Directions: Decide whether each statement refers to apparent magnitude, absolute magnitude, or both. Complete the Venn diagram by writing the number of each statement in the correct section. Each statement is used only once. Apparent Magnitude Both Absolute Magnitude 1. Luminosity is the true brightness of an object. It is the amount of energy a body radiates per unit of time. 2. Astronomers can measure how bright stars are. 3. The Sun is the brightest object in the sky. 4. depends on a star s temperature and size, not its distance from Earth 5. does not describe a star s actual brightness 6. The brightness of a star is described using a scale with positive and negative numbers. 7. On a star magnitude scale, stars with higher numbers are less bright. 8. can be calculated from a star s distance and apparent magnitude 9. depends on a star s distance from Earth 10. originally described by the Greek astronomer Hipparchus 11. The lower a star s absolute magnitude is, the higher its luminosity will be. 12. brightness as seen by an observer on Earth 20 Stars and Galaxies

15 Enrichment LESSON 1 Wayfinding and Timekeeping with the Stars Before Europeans developed navigational instruments that would allow them to venture into the open ocean, their travels by ship were limited to sailing close to the coastlines of continents. However, before the common era, voyagers from Fiji, Tonga, and Samoa were able to navigate without instruments and settled islands in an ocean area of more than 10 million square miles. The Polynesians and the Stars Polynesian navigators used the rising and setting points of celestial bodies to find directions. During the day, the Sun gave directional points, rising in the east, and setting in the west. At night, navigators held their course by orienting their canoes to the rising and setting points of stars on the eastern and western horizons. They also used pointer stars and the meridian. The meridian is an imaginary line that is perpendicular to the horizon; pairs of stars that cross the meridian at the same time point north and south. The Regiment of the North Christopher Columbus observed the sky to keep time. Columbus understood the Sun s path through the sky. The Sun and the stars move 15 degrees each hour from rising to setting. Applying Critical-Thinking Skills Directions: Answer each question or respond to each statement. All navigators of this period used the Regiment of the North to keep track of elapsed time. To visualize this system, draw a person inside a circle, with the head at the top, feet at the bottom, and each arm stretched with fingers pointing to the 3 o clock and 9 o clock positions. Draw the North Star above the person s head and lines through the person, with 45-degree angles between them. (Draw a vertical and horizontal line bisecting the circle. Add two diagonal lines, each one bisecting two of the quarter-circles. There should be 8 equal parts, each with a 45-degree angle.) The two brightest, outermost stars of the Little Dipper, called the Guards, move 15 degrees every hour as they revolve counterclockwise. If the Guards move from the person s head to foot, they have moved 180 degrees, or 4 lines, or 12 hours. If the stars moved 3 lines, then 9 hours had passed. On Sept. 30, 1492, Columbus wrote in his log: the Guards are slightly below the arm on the west at night but at daybreak appear below the arm to the east. If this observation is correct, it appears that I only proceeded three lines last night, or nine astronomical hours. 1. Describe In relation to the front, back, right, and left sides of your body, which directions would you point your canoe if you wanted to go (a) north, (b) south, (c) east, and (d) west when the Sun is rising to your right? Explain your answers. 2. Calculate Using the Regiment of the North, how much time has elapsed when the Guards have moved from the head to halfway between the hand and the foot on the west? Explain how you got your answer. Stars and Galaxies 21

16 Challenge LESSON 1 Where is the Sun? Early civilizations used the Sun s movements to tell the time of day and anticipate the change of seasons. Observe the Sun s Movement Never look directly at the Sun! Even looking at the Sun with dark sunglasses or through a dark filter can damage your eyes. In this activity, you will observe indirectly the movement of the Sun in the sky. Begin early on a sunny day and plan to make periodic measurements throughout the day. 1. You will need a 2 ' by 3' piece of heavy paper or a large, flat sheet of cardboard; a large container of soil or stone; a meterstick (or a tall, heavy object such as a glass bottle); a marker; and a compass. 2. Find an outdoor space that is not occupied or shaded throughout the day. 3. At your spot, determine which direction is north. Place the cardboard or heavy paper on level ground with the top edge facing north. Mark the directions east, west, and south on the paper and arrange it so it does not move. Place the meterstick upright in the container and put it at the center of the southern edge of the paper. 4. On the paper, mark the line and the tip of the shadow that is cast by the meterstick with a marker and record the time of the observation. 5. Every hour during the course of the day (or 9:30 A.M., noon, and 2:30 P.M. if you can t do it every hour), record the movement of the shadow of the meterstick by marking the line and top of the shadow. Each time you mark the meterstick s shadow, also note the time on the paper. 6. On a fresh sheet of paper, draw a diagram of the times and lengths of the shadows you recorded. Explain how the shadows changed in size and direction over the course of the day. 7. Imagine you are a member of an early civilization that has no technology to keep time. You have noticed how the shadows change as the Sun moves across the sky. Invent a way to tell the approximate time of day. To start, decide what you would use as a unit of time. 22 Stars and Galaxies

17 Skill Practice Interpret Scientific Illustrations LESSON 1: 30 minutes How can you use scientific illustrations to locate constellations? You might have heard that stars in the Big Dipper point to Polaris. The Big Dipper is a small star pattern in the larger constellation of Ursa Major. Ursa Major means big bear in Latin. It is the third-largest of the 88 modern constellations in the sky. Study the image of Ursa Major. Can you find the seven stars that form the Big Dipper? You can use a star finder to locate stars on any clear night of the year. The star finder also helps you see how constellations move across the sky. Materials star finder Learn It Scientific illustrations can help you understand difficult or complicated subjects. Interpret scientific illustrations on the star finder to learn about the night sky. Try It 1. Read and complete a lab safety form. 2. Read the user information provided with the star finder. 3. Rotate the wheel until the star finder is set to the day and time when you will be viewing the night sky. Observe how the ancient constellations marked on the star finder move. 4. Make a list of the bright stars, constellations, and planets you might be able to see in the sky. 5. Use the star finder outdoors on a clear night. As you hold the star finder overhead, be sure the arrows are pointing in the correct directions. Apply It 6. What ancient constellations, planets, and stars were you able to see? 7. Did you locate Polaris? Why will you be able to see Polaris 6 months from now? Stars and Galaxies 23

18 Skill Practice continued 8. Which constellations won t you be able to see 6 months from now? 9. Why do stars appear to move? 10. How might ancient constellations have helped people in the past? 11. Key Concept How does dividing the sky into constellations help scientists study the sky? 24 Stars and Galaxies