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How to Use This Presentation • To View the presentation as a slideshow with effects select “View” on the menu bar and click on “Slide Show.” • To advance through the presentation, click the right-arrow key or the space bar. • From the resources slide, click on any resource to see a presentation for that resource. • From the Chapter menu screen click on any lesson to go directly to that lesson’s presentation. • You may exit the slide show at any time by pressing the Esc key. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Resources Bellringers Chapter Presentation Transparencies Standardized Test Prep Visual Concepts Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 The Universe Table of Contents Section 1 The Life and Death of Stars Section 2 The Milky Way and Other Galaxies Section 3 Origin of the Universe Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars Objectives • Describe the basic structure and properties of stars. • Explain how the surface temperature of a star is measured. • Recognize that all normal stars are powered by fusion reactions that form elements. • Identify the stages in the evolution of stars. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars Bellringer Based on what you have learned, as well as previous knowledge, write answers for the following items: 1. People have studied the stars for centuries. The ancient Greeks gave names to groups of stars called constellations. Make a list of at least five constellations. 2. Explain why scientists collect information from electromagnetic waves, such as visible light, microwaves, and X rays, to study stars. 3. Stars do not all look the same. Some are brighter than others, and many have different colors. Write a paragraph suggesting the causes of these differences. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars What Are Stars? • Star a large celestial body that is composed of gas and that emits light; the sun is a typical star • Light-year the distance that light travels in one year; about 9.5 trillion kilometers • Stars are huge spheres of hot gas. • The nearest star to the Earth is the sun. • We use the unit light-year to describe a star’s distance from Earth. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars What Are Stars? continued • Stars are driven by nuclear fusion reactions. • The core of a star is extremely hot, extremely dense, and under extreme pressure. • Nuclear fusion takes place in the core of a star. • Fusion combines the nuclei of hydrogen atoms into helium. • When two particles fuse, energy is released. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars Constellation Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars Nuclear Fusion Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars What Are Stars? continued • Energy moves slowly through the layers of a star. • Energy moves through the layers of a star by convection and radiation. • Convection rising hot gas moves upward, away from the star’s center, and cooler gas sinks toward the center • Radiation atoms absorb energy and transfer it to other atoms in random directions; atoms near the star’s surface radiate energy into space. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars Structure of the Sun Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars Structure of the Sun Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars The Sun’s Atmosphere Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars Studying Stars • Why do some stars appear brighter than others? • The brightness of a star depends on the star’s temperature, size, and distance from Earth. • The brightest star in the night sky, Sirius, appears so bright because it is relatively close to Earth. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars Studying Stars, continued • We learn about stars by studying light. • Stars produce a full range of electromagnetic radiation, from high-energy X-rays to low-energy radio waves. • Scientists use optical telescopes to study visible light and radio telescopes to study radio waves emitted from astronomical objects. • Earth’s atmosphere blocks some wavelengths, so telescopes in space can study a wider range of the spectrum. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars Studying Stars, continued • A star’s color is related to its temperature. • Hotter objects glow with light that has shorter wavelengths (closer to the blue end of the spectrum). • Cooler objects glow with light that has longer wavelengths (closer to the red end of the spectrum.) Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars Starlight Intensity Graph Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars Studying Stars, continued • Spectral lines reveal the composition of stars. • The spectra of most stars have dark lines caused by gases in the outer layers that absorb light at that wavelength. • Each element produces a unique pattern of spectral lines. • Astronomers can match the dark lines in starlight to the known lines of elements found on Earth. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars The Fate of Stars • The sun formed from a cloud of gas and dust. • Stars are born, go through different stages of development, and eventually die. • The sun formed about 5 billion years ago. • Stars appear different from one another in part because they are at different stages in their life cycles. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars The Fate of Stars, continued • The sun now has a balance of inward and outward forces • The fusion reactions in the core of the sun produce an outward force that balances the inward force due to gravity. • Over time, the percentage of the sun’s core that is helium becomes larger. • Eventually the core will run out of hydrogen and the sun will begin to die. • Scientists estimate that the sun can continue nuclear fusion for another 5 billion years. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars The Fate of Stars, continued • The sun will become a red giant before it dies. • As fusion slows, the outer layers of the sun will expand. • The sun will become a red giant. • Red giant a large, reddish star late in its life cycle • When the sun runs out of helium, the outer layers will expand and eventually leave the sun’s orbit. • The sun will become a white dwarf. • White dwarf a small, hot dim star that is the leftover center of an old star. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars The Fate of Stars, continued • Supergiant stars explode in supernovas. • Massive stars evolve faster, develop hotter cores, and create heavier elements through fusion. • A supergiant forms iron at it’s core. • Eventually the core collapses and then explodes in a Type II supernova. • Supernova a gigantic explosion in which a miassive star collapses and throws its outer layers into space, plural supernovae Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars The Fate of Stars, continued • A Type I supernova occurs when a white dwarf in a binary system (a system composed of two stars) collects enough mass from its companion to exceed 1.4 solar masses. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars The Fate of Stars, continued • After a Type II supernova, either a neutron star or a black hole forms. • If the core that remains after a supernova has a mass of 1.4 to 3 solar masses, the remnant can become a neutron star. • If the leftover core has a mass that is greater than three solar masses, it will collapse to form a black hole. • Black hole an object so massive and dense that not even light can escape its gravity Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars The Fate of Stars, continued • The H-R diagram shows how stars evolve. • The vertical line on an H-R diagram indicates brightness in absolute magnitude. • The horizontal line on the H-R diagram indicates temperature. • Most stars appear in a diagonal line called the main sequence. • As stars age and pass through different stages, their positions on the H-R diagram change. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars H-R Diagram Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 1 The Life and Death of Stars Types of Stars Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 2 The Milky Way and Other Galaxies Objectives • Define galaxy, and identify Earth’s home galaxy. • Describe two characteristics of a spiral galaxy. • Distinguish between the three types of galaxies. • Describe two aspects of a quasar, and identify the tools scientists use to study quasars. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 2 The Milky Way and Other Galaxies Bellringer Based on what you have learned, as well as previous knowledge, answer the following questions: 1. What types of objects would you expect to find within a galaxy? 2. Do you think that the same force that keeps our solar system together keeps galaxies together? Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 2 The Milky Way and Other Galaxies Bellringer, continued 3. Do you think that the components of galaxies move in a random and unpredictable motion, or do they move in an ordered and predictable one? 4. The word galaxy comes from the Greek word for “milk,” and the star-rich region of our own galaxy has long been called the Milky Way. Other galaxies, before they were recognized as containing stars, were called nebulas, from the Latin for “clouds.” What do you think was the reason these starry regions were described in these terms? Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 2 The Milky Way and Other Galaxies Galaxies • Galaxies contain millions or billions of stars. • Galaxy a collection of stars, dust, and gas bound together by gravity • Because stars age at different rates, a galaxy may contain many types of stars. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 2 The Milky Way and Other Galaxies Galaxies, continued • Gravity holds galaxies together in clusters. • Galaxies are not spread evenly throughout space. • Cluster a group of stars or galaxies bound by gravity • The Milky Way galaxy and the Andromeda galaxy are two of the largest members of the Local Group, a cluster of more than 30 galaxies. • Clusters of galaxies can form even larger groups, called superclusters. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 2 The Milky Way and Other Galaxies Types of Galaxies • We live in the Milky Way galaxy. • Edwin Hubble divided all galaxies into three major types: spiral, elliptical, and irregular. • Most of the objects visible in the night sky are part of the Milky Way galaxy. • Scientists use astronomical data to piece together a picture of the Milky Way galaxy. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 2 The Milky Way and Other Galaxies Types of Galaxies, continued • The Milky Way is a spiral galaxy. • Our galaxy is a huge spiraling disk of stars, gas, and dust. • Our solar system is located within a spiral arm. • The nucleus of the galaxy is dense and has many old stars. • The gas and dust is called interstallar matter. • Interstellar matter the gas and dust located between the stars in a galaxy. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 2 The Milky Way and Other Galaxies Types of Galaxies, continued • Eliptical galaxies have no spiral arms. • Elliptical galaxies are spherical or egg shaped. • They contain mostly older stars and have little interstellar matter. • Because older stars are red, elliptical galaxies often have a reddish color. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 2 The Milky Way and Other Galaxies Types of Galaxies, continued • All other galaxies are irregular galaxies. • Irregular galaxies lack regular shapes and do not have a well-defined structure. • Some irregular galaxies may be oddly shaped because the gravitational influence of nearby galaxies distorts their spiral arms. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 2 The Milky Way and Other Galaxies Investigating Different Types of Galaxies Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 2 The Milky Way and Other Galaxies How Galaxies Evolve • Quasars may be infant galaxies. • In 1960, a faint object was matched with a strong radio signal. This object was called a quasar. • quasar quasi-stellar radio sources; very luminous objects that produce energy at a high rate and that are thought to be the most distant objects in the universe • Each quasar has a huge central black hole and a large disk of gas and dust around it. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 2 The Milky Way and Other Galaxies How Galaxies Evolve, continued • Galaxies change over time. • Galaxies change as they use up their stores of gas and dust • Galaxies also change as a result of collisions. • As galaxies approach each other, mutual gravitational attraction changes their shape. • Collisions of gas and dust may cause new stars to begin forming. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 2 The Milky Way and Other Galaxies Formation of the Solar System Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 2 The Milky Way and Other Galaxies Lunar Phases Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 2 The Milky Way and Other Galaxies Solar and Lunar Eclipses Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe Objectives • Describe the basic structure of the universe. • Describe red shift, and explain what it tells scientists about our universe. • State the main features of the big bang theory, and explain the evidence supporting the expansion of the universe. • Explain how scientists are using tools and models to hypothesize what may happen to the universe in the future. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe Bellringer Based on what you have learned, as well as previous knowledge, answer the following questions: 1. What types of objects would you expect to find within a galaxy? 2. Do you think that the same force that keeps our solar system together keeps galaxies together? Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe Bellringer 3. Do you think that the components of galaxies move in a random and unpredictable motion, or do they move in an ordered and predictable one? 4. The word galaxy comes from the Greek word for “milk,” and the star-rich region of our own galaxy has long been called the Milky Way. Other galaxies, before they were recognized as containing stars, were called nebulas, from the Latin for “clouds.” What do you think was the reason these starry regions were described in these terms? Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe What Is the Universe? • Universe the sum of all space, matter, and energy that exist, that have existed in the past, and that will exist in the future. • You are part of the universe, as is Earth and everything on it. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe Cosmology Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe What is the Universe? continued • We see the universe now as it was in the past. • It takes time for light to travel in space. • The farther away an object is, the older the light that we receive from that object. • Most of the universe is empty space • Space is a vacuum with no air and no air pressure. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe What Happened at the Beginning? • The universe is expanding. • Observations of spectral lines from other galaxies indicated that they were moving away from us • Red shift an apparent shift toward longer wavelengths of light caused when a luminous object moves away from the observer • Blue shift an apparent shift toward shorter wavelengths of light caused when a luminous object moves toward the observer Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe Red Shift Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe What Happened at the Beginning? continued • Expansion implies that the universe was once smaller. • Long ago, the entire universe might have been contained in an extremely small space. • All of the matter in the universe appears to expand rapidly outward, like a gigantic explosion • Scientists call this hypothetical explosion the big bang. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe Universal Expansion Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe What Happened at the Beginning? continued • Did the universe start with a big bang? • Scientists have proposed several different theories to explain the expansion of the universe. • The most complete and widely accepted theory is the big bang theory. • Big bang theory the theory that all matter and energy in the universe was compressed into an extremely small volume that 10 to 20 billion years ago exploded and began expanding in all directions Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe Big Bang Theory Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe What Happened at the Beginning? continued • Cosmic background radiation supports the big bang theory. • Cosmic background radiation is a steady but very dim signal from all over the sky in the form of radiation at microwave wavelengths. • Many scientists believe that the microwaves are dim remnants of the radiation produced during the big bang. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe What Happened at the Beginning? continued • Radiation dominated the early universe. • According to the big bang theory, expansion cooled the universe enough for matter such as protons, neutrons, and electrons to form. • Processes in stars lead to bigger atoms. • Once hydrogen atoms formed, stars and galaxies began to form, too. • All elements other than hydrogen and helium form in stars. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe Predicting the Future of the Universe • The future of the universe is uncertain. • • The universe is expanding, but the combined gravity of all the mass in the universe is also pulling the universe inward. The competition between these forces leaves three possibilities: 1. The universe will keep expanding forever 2. The expansion of the universe will gradually slow down, and the universe will approach a limit in size. 3. The universe will stop expanding and start to fall back in on itself Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe Predicting the Future of the Universe, continued • The fate of the universe depends on mass. • If there is not enough mass, the gravitational pull will be too small to stop the expansion. • If there is just the right amount of mass, the expansion will continually slow down, but will never stop completely. • If there is too much mass, gravity will eventually overcome expansion and the universe will contract. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe Predicting the Future of the Universe, continued • New technology helps scientists test theories. • Powerful telescopes and other sensitive equipment help scientists study the universe. • Scientists make observations to test theories and develop new explanations. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe Predicting the Future of the Universe, continued • There is a debate about dark matter. • There is more matter in the universe than what is visible. • Scientists call this dark matter. • Dark matter may be planets, black holes, or brown dwarfs (starlike objects that lack enough mass to begin fusion.) Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe Predicting the Future of the Universe, continued • Scientists use mathematics to build better models. • Theories can be expressed in mathematical form. • Mathematical models can be used to help test theories that are not easily observed. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe Contents of Galaxies Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe Structure of the Universe Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Section 3 Origin of the Universe Concept Mapping Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Standardized Test Prep Understanding Concepts 1. Light travels 9.5 X 1015 meters in one year. Express the distance between the sun and its nearest neighbor, Alpha Centauri—4.1X1016 meters—in terms of light years. A. B. C. D. 0.43 2.2 4.3 22.0 Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Standardized Test Prep Understanding Concepts, continued 1. Light travels 9.5 X 1015 meters in one year. Express the distance between the sun and its nearest neighbor, Alpha Centauri—4.1X1016 meters—in terms of light years. A. B. C. D. 0.43 2.2 4.3 22.0 Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Standardized Test Prep Understanding Concepts, continued 2. Toward which end of the spectrum is the light of a receding galaxy shifted? F. G. H. I. blue green red yellow Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Standardized Test Prep Understanding Concepts, continued 2. Toward which end of the spectrum is the light of a receding galaxy shifted? F. G. H. I. blue green red yellow Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Standardized Test Prep Understanding Concepts, continued 3. A star, such as the sun, in the middle of the main sequence, remains at equilibrium for billions of years before it changes. What forces keep the star from shrinking or expanding during that period? Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Standardized Test Prep Understanding Concepts, continued 3. A star, such as the sun, in the middle of the main sequence, remains at equilibrium for billions of years before it changes. What forces keep the star from shrinking or expanding during that period? Answer: The equilibrium is a result of the force of gravity, which pulls material inward, and the energy produced by fusion, which pushes material outward. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Standardized Test Prep Reading Skills When a very large star collapses, it can form a black hole. Inside a black hole, mass is so dense that even light cannot reach the escape velocity of its gravitational field. A black hole with a mass ten times as great as the sun would have a radius of only about 30 kilometers. Matter that strikes a black hole becomes part of its mass. Black holes are detected by their gravitational effects on matter around them. 4. Why can black holes only be observed by their effects and not by direct observation through a large telescope? Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Standardized Test Prep Reading Skills, continued 4. [See previous slide for question.] Answer: Because no light can escape from the black hole, it cannot be directly observed. Direct observation of a distant object can only be made by collecting electromagnetic radiation that it emits or reflects. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Standardized Test Prep Interpreting Graphics Base your answers to questions 5 through 8 on the illustration below. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Standardized Test Prep Interpreting Graphics, continued 5. Which of these stars is most likely to become a white dwarf in the near future? A. B. C. D. Betelgeuse Sirius Proxima Centauri Alpha Centauri Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Standardized Test Prep Interpreting Graphics, continued 5. Which of these stars is most likely to become a white dwarf in the near future? A. B. C. D. Betelgeuse Sirius Proxima Centauri Alpha Centauri Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Standardized Test Prep Interpreting Graphics, continued 6. Why does Sirius appear brighter in the night sky than Betelgeuse? F. Sirius is a brighter star than Betelgeuse. G. Betelgeuse is farther from Earth than Sirius. H. Betelgeuse is cooler than Sirius, so it does not emit as much light. I. Sirius has a smaller diameter, so it is a more concentrated light source. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Standardized Test Prep Interpreting Graphics, continued 6. Why does Sirius appear brighter in the night sky than Betelgeuse? F. Sirius is a brighter star than Betelgeuse. G. Betelgeuse is farther from Earth than Sirius. H. Betelgeuse is cooler than Sirius, so it does not emit as much light. I. Sirius has a smaller diameter, so it is a more concentrated light source. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Standardized Test Prep Interpreting Graphics, continued 7. Which type of star would more likely be found in the arms of the Milky Way than in its core? A. B. C. D. red giants white dwarfs green main sequence stars yellow main sequence stars Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Standardized Test Prep Interpreting Graphics, continued 7. Which type of star would more likely be found in the arms of the Milky Way than in its core? A. B. C. D. red giants white dwarfs green main sequence stars yellow main sequence stars Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Standardized Test Prep Interpreting Graphics, continued 8. Which of these stars would appear to be brightest if all of them were observed from the same distance? F. G. H. I. Aldebaran Canopus Sun Vega Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 20 Standardized Test Prep Interpreting Graphics, continued 8. Which of these stars would appear to be brightest if all of them were observed from the same distance? F. G. H. I. Aldebaran Canopus Sun Vega Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.