Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Table of Contents Stars and Galaxies Section 1 • Observing the Universe Section 2 • Evolution of Stars Section 3 • Galaxies and the Milky Way Section 4 • Cosmology Section 1 Observing the Universe Constellations • Long ago, people named patterns of stars after characters in stories, animals and even tools. • Many of the names given to these star patterns by ancient cultures survive today and are called constellations. Section 1 Observing the Universe Telescopes • Many stars are visible with the unaided eye. • However, to see some stars and other distant objects better, you need a telescope. • Optical telescopes are used to study objects in visible light, and radio telescopes are used to study objects in the radio wavelengths. Section 1 Observing the Universe Optical Telescopes • There are two basic types of optical telescopes. • One type uses only lenses to collect and focus light and the other uses lenses and mirrors. • The distance from the objective lens to the focus is the focal length of the telescope. Section 1 Observing the Universe Refracting Optical Telescopes • A refracting telescope uses a convex lens. • Light passes through the objective lens and the eyepiece lens. • The eyepiece then magnifies the image. Section 1 Observing the Universe Reflecting Optical Telescopes • A reflecting telescope uses a mirror as an objective to collect and focus light. • The figure shows how light passes through the open end of a reflecting telescope and strikes a concave mirror at the base of the telescope. Section 1 Observing the Universe Focal Point and Focal Length • You can calculate the magnifying power (Mp) of a telescope by dividing the focal length of the objective (fo) by the focal length of the eyepiece (fe). Mp = fo/fe Section 1 Observing the Universe Adaptive Optics • The most recent innovations in optical telescopes involve adaptive optics. • In an adaptive optics system, the light from the objective mirror strikes a small, deformable mirror before it is focused, which reduces distortion. Section 1 Observing the Universe Radio Telescopes • A telescope that collects and amplifies radio waves is a radio telescope. • Because radio waves have long wavelengths, a radio telescope must be built with a very large objective, usually some form of dish antenna. • The very large array near Socorro, New Mexico has 27 radio telescopes that detect and amplify radio waves from distant objects in space. Section 1 Observing the Universe Space Telescopes • Earth’s atmosphere limits what ground-based telescopes can achieve. • For this reason, astronomers use space-based telescopes, such as the Chandra X-Ray Observatory and the Spitzer Space Telescope. • Large distances in space are measured in a unit called a light-year, the distance that light travels in one year. Section 1 Observing the Universe The Light-Year • Light travels at a speed of 300,000 km/s in space. • It takes millions to billions of years for light from distant objects to reach Earth. Section 1 Observing the Universe Spectroscopes • A spectroscope uses a prism or diffraction grating to disperse the light into its component wavelengths. • The separated wavelengths are called the spectrum of the star. • The spectrum can determine a star’s chemical composition, its surface temperature, and whether it is moving away from or toward Earth. Section 1 Section Check Question 1 A refracting telescope uses a _______ as an objective. A. mirror B. wave C. convex lens D. laser Section 1 Section Check Answer The answer is C. Convex lens are curved outward like the surface of a ball. Section 1 Section Check Question 2 What does a spectroscope do? Answer A spectroscope disperses the light from a star or other celestial object collected by a telescope into an electromagnetic spectrum. Section 1 Section Check Question 3 What is the distance that light travels in one year? A. 15 million km B. 9.5 trillion km C. 12 billion km D. 2 million km Section 1 Section Check Answer The answer is B. Large distances in space are measured in a unit called a light-year, which is equal to 9.5 trillion km. Section 2 Evolution of Stars How do stars form? • Stars form from a large cloud of gas, ice, and dust called a nebula. • The nebula contracts, and a protostar forms in the center of the cloud. Section 2 Evolution of Stars H-R Diagram • In the early 1900s, Ejnar Hertzsprung and Henry Russell studied the relationship between the brightness and temperature of stars. • As stars form, they can be plotted on the HertzsprungRussell (H-R) diagram. Section 2 Evolution of Stars H-R Diagram • About 90 percent of all stars fall on a region from the upper left to the lower right of the HR diagram called the main sequence. Section 2 Evolution of Stars How do stars evolve? • A protostar continues to collapse until nuclear fusion begins. • Equilibrium is the balance between outward pressure exerted by fusion and inward pressure due to gravity. Section 2 Evolution of Stars Main Sequence • Once equilibrium is reached, the star becomes a main sequence star. • When a star uses up all the hydrogen in its core, it is no longer in a state of equilibrium. Section 2 Evolution of Stars Giants and Dwarfs • When hydrogen in a star’s core is used up, its outward pressure is overcome by gravity. • Its core contracts and increases in temperature. • The outer layers expand and cool. • In this late stage of its life cycle, an average star like our Sun is called a giant star. Section 2 Evolution of Stars Giants and Dwarfs • Now the star is enormous and its surface is much cooler. • When the core temperature reaches 100 million K, helium fuses, forming carbon. • Its outer layers escape into space leaving behind the hot, dense core that continues to contract. Section 2 Evolution of Stars Giants and Dwarfs • A white dwarf forms as the core of a giant star collapses and the star’s outer layers escape into space. • A white dwarf is hot with a dense core. Section 2 Evolution of Stars Supergiants, Neutron Stars, and Black Holes • When the core of stars over eight times more massive than our Sun reach temperatures high enough to cause fusion that produce heavier elements, the star expands into a supergiant. • Fusion reactions end when iron accumulates in the star’s core. Section 2 Evolution of Stars Supergiants, Neutron Stars, and Black Holes • A supernova is a gigantic explosion in which the temperature in the collapsing core reaches 10 billion K and atomic nuclei are split into neutrons and protons. • A collapsing star can also evolve into a neutron star when protons and electrons in the star’s core collide to form neutrons. Section 2 Evolution of Stars Supergiants, Neutron Stars, and Black Holes • Very massive stars, with masses greater than 25 times the mass of the Sun collapse to form a black hole. • A black hole is an area of space that is so dense that nothing can escape the inward pull of gravity. Section 2 Evolution of Stars The Sun—A Main Sequence Star • The Sun’s interior can be divided into several distinct layers: the core, the radiation zone, and the convection zone. Section 2 Evolution of Stars The Sun’s Interior • The innermost layer of the Sun is the core. The temperature inside the core is about 15 million degrees K. This is where fusion occurs. • The layer of the Sun just above the core is the radiation zone. Section 2 Evolution of Stars The Sun’s Interior • Thermal energy produced by nuclear fusion in the core is transferred through the radiation zone to the convection zone. • Columns of hot material form convection cells as they rise to the surface, cool, and sink back down. Section 2 Evolution of Stars Surface Features of the Sun • The surface of the Sun is called the photosphere. • This is the layer of the Sun that gives us light. • The atmosphere above the photosphere is composed of the chromosphere and the corona. Section 2 Evolution of Stars Granules and Sunspots • The Sun’s photosphere, or surface is at the top of the convection zone and has a mottled appearance, called granulation. • These darker areas of the Sun’s photosphere, called sunspots are cooler than surrounding areas. • Sunspots are not permanent features of the Sun. • They appear and disappear over periods of days, weeks, or months. Section 2 Evolution of Stars Prominences and Flares • Intense magnetic fields associated with sunspots can cause huge arching columns of gas called prominences to erupt. • Gases near a sunspot sometimes brighten suddenly, shooting gas outward at high speed in what are called solar flares. Section Evolution of Stars 2 CMEs • Sometimes large bubbles of electrically-charged gas are emitted from the Sun. These are known as CMEs (coronal mass ejections). • Earth’s atmosphere protects from CMEs. • Auroras take place when high-energy particles in CMEs interact with Earth’s magnetic field. Section 2 Section Check Question 1 How do stars form? Answer Stars form from a large cloud of gas, ice, and dust. Once the temperature inside a contracting nebula reaches 10 million, fusion begins. Section 2 Section Check Question 2 Which is NOT a layer of the Sun’s interior? A. the core B. the radiation zone C. the convection zone D. sunspots Section 2 Section Check Answer The answer is D. The Sun’s interior can be divided into several distinct layers or zone: the core, the radiation zone, and the convection zone. Section 2 Section Check Question 3 What is a sunspot? Answer Sunspots are dark, cool areas in the photosphere where the Sun’s magnetic field has weakened. Section 3 Galaxies and the Milky Way Galaxies • A galaxy is a large group of stars, gas, and dust held together by gravity. • Our galaxy, called the Milky Way Galaxy contains 200 billion and 400 billion stars, by most recent estimates, including the Sun. Section 3 Galaxies and the Milky Way Spiral Galaxies • Spiral galaxies are disk-shaped and have spiral arms that radiate outward from the galaxy’s center. • These spiral arms are star forming regions that contain clouds of ice, dust, and gas. • Spiral galaxies have a central bulge, or nucleus, where stars are closer together. • They range in size from 20,000 to 200,000 light-years across. Section 3 Galaxies and the Milky Way Elliptical Galaxies • Elliptical galaxies are round and have shapes that range from spherical to football-shaped. • Less star formation occurs in an elliptical galaxy because they contain less gas, ice, and dust. Section 3 Galaxies and the Milky Way Irregular Galaxies • Galaxies that are not elliptical or spiral are considered irregular galaxies. • They take many different shapes and contain 100 million to 10 billion stars, making them larger than dwarf ellipticals but smaller than spirals. Section 3 Galaxies and the Milky Way The Local Group • Just as stars are grouped together within galaxies, galaxies are grouped into clusters. • Our Milky Way galaxy belongs to a cluster called the Local Group. • It is a relatively small cluster containing about 50 galaxies spread out over a diameter of 10 million lightyears across. Section 3 Galaxies and the Milky Way How do galaxies form? • Astronomers hypothesize that the first galaxies began to form 13.7 billion years ago. • Astronomers believe that the first galaxies that formed tended to be irregular in shape, smaller, and closer together than galaxies today. Section 3 Galaxies and the Milky Way The Milky Way • The Milky Way galaxy measures about 100,000 lightyears in diameter. The Sun lies about 28,000 lightyears from the galactic center on the edge of one the spiral arms. • The oldest stars in the Milky Way are thought to be 9 to 10 billion years old. Section 3 Galaxies and the Milky Way The Nuclear Bulge • Stars are much closer together in the central region of a spiral galaxy compared to its arms. • The region where stars are closely clustered is called the nuclear bulge. Section 3 Galaxies and the Milky Way The Halo and Galactic Center • The halo is a spherical region that surrounds the nuclear bulge. • The galactic center of the Milky Way emits a tremendous amount of energy and could be a black hole. Section 3 Section Check Question 1 Which is NOT a type of galaxy? A. elliptical B. irregular C. round D. spiral Section 3 Section Check Answer The answer is C. “Round” is not recognized as a major type of galaxy. Section 3 Section Check Question 2 How do galaxies grow? A. by producing new stars B. by emitting light C. by absorbing other galaxies D. by absorbing stars that don’t belong to other galaxies Section 3 Section Check Answer The answer is C. The Milky Way has been gobbling up the Sagittarius dwarf elliptical galaxy for 2 billion years. Section 3 Section Check Question 3 Where is the Sun located in the Milky Way galaxy? A. 28,000 light-years from the center of the galaxy B. at the edge of one of the spiral arms C. 100,000 light-years from the center D. 1,000 light-years from the center Section 3 Section Check Answer The answer is B. The Sun lies about 26,000 light-years from the center of the galaxy on the edge of one of the spiral arms. Section 4 Cosmology The Expanding Universe • The study of the universe—how it began, how it evolves, and what it is made of—is called cosmology. Section 4 Cosmology Evidence of the Big Bang • The theory that all matter and energy in the universe were compressed into a single point which began to expand outward is called the big bang theory. • It states that the universe started with a big bang, or explosion, and has been expanding ever since. • The big bang is not like an explosion of matter into empty space; it is the rapid expansion of space. Section 4 Cosmology Cosmic Microwave Background Radiation • Cosmic background radiation is the residual radiation from the formation of the universe. • Data from the Wilkinson Microwave Anisotropy Probe indicate that the big bang occurred 13.7 billion years ago. Section 4 Cosmology The Doppler Effect • The motion of the stars within the Milky Way can be detected by using the Doppler effect. • Doppler shifts occur in light as well as sound. Section 4 Cosmology The Doppler Effect • If a star approaches Earth, its wavelengths of light are compressed, causing a blue shift. If a star moves away, its wavelengths are stretched, causing a red shift. Section 4 Cosmology What is the universe made of? • Visible or otherwise detectable mass, called regular matter, appears to make up only a very small amount of the known universe. • Dark matter is an invisible form of matter that does not emit any detectable electromagnetic radiation. • Observations show that there is about five to six times as much dark matter in the universe as regular matter. Section Cosmology 4 Dark Energy • Data indicate that the expansion of the universe is accelerating. • Explaining this acceleration is difficult. • Dark energy is an invisible form of energy that causes a repulsive force causing the universe to accelerate faster. Section 4 Section Check Question 1 When did the universe begin? A. 13.7 billion years ago B. 5 million years ago C. 25 trillion years ago D. 14 trillion years ago Section 4 Section Check Answer The answer is A. The Wilkinson Microwave Anisotropy Probe team proposed that the universe began about 13.7 billion years ago with a big bang. Section 4 Section Check Question 2 What causes the Hubble redshift? Answer The Hubble redshift is caused by the expansion of space, not the movement of galaxies. Section 4 Section Check Question 3 ______ might be causing accelerated expansion of the universe. A. Kinetic energy B. Potential energy C. Dark energy D. Thermal energy Section 4 Section Check Answer The answer is C. Dark energy explains the accelerated expansion of the universe. Help To advance to the next item or next page click on any of the following keys: mouse, space bar, enter, down or forward arrow. Click on this icon to return to the table of contents. Click on this icon to return to the previous slide. Click on this icon to move to the next slide. Click on this icon to open the resources file. Click on this icon to go to the end of the presentation. End of Chapter Summary File Chapter Resources Click on one of the following icons to go to that resource. connected.mcgraw-hill.com/ Image Bank Video Clips and Animations Chapter Summary Chapter Review Questions Standardized Test Practice Image Bank Click on individual thumbnail images to view larger versions. Image Bank Constellations THUMBNAILS Image Bank Refracting Telescope THUMBNAILS Image Bank Reflecting Telescope THUMBNAILS Image Bank Hertzsprung-Russell Diagram THUMBNAILS Image Bank Main Sequence Stars THUMBNAILS Image Bank The Sun THUMBNAILS Image Bank Milky Way THUMBNAILS Image Bank Doppler Effect THUMBNAILS Video Clips and Animations Reviewing Main Ideas Observing the Universe • Constellations are patterns of stars that resemble things familiar to the observer. • Optical telescopes collect and focus visible light and magnify viewed objects. Reviewing Main Ideas Observing the Universe • A refracting telescope uses lenses to collect light and magnify the image, and a reflecting telescope uses a mirror to collect light and a lens to magnify the image. • A radio telescope collects and amplifies radio waves. Reviewing Main Ideas Evolution of Stars • Stars form from a large cloud of gas, ice, and dust, called a nebula. When the temperature inside the contracting nebula reaches 10 million K, fusion begins, and a star is born. • Stars are classified as main sequence stars, giant stars, and white dwarfs on the H-R diagram. Reviewing Main Ideas Evolution of Stars • When a star reaches stellar equilibrium it is considered a main sequence star. When the hydrogen fuel is depleted, a star loses equilibrium and evolves into a giant stars or supergiant. Reviewing Main Ideas Evolution of Stars • After losing its outer layers, a giant star becomes a white dwarf. A supergiant can evolve into a neutron star or a black hole. • The Sun’s energy is produced at its core by nuclear fusion. Reviewing Main Ideas Galaxies and the Milky Way • A galaxy is a large group of stars, gas, and dust held together by gravity. The Local Group of galaxies is a cluster that contains the Milky Way galaxy. • The three main types of galaxies form by absorbing or merging with smaller objects. They continue to evolve by colliding or merging with other galaxies. • The Milky Way galaxy is about 100,000 light-years across and the Sun lies about 28,000 light-years from its center. Reviewing Main Ideas Cosmology • The Big Bang theory is the most accepted theory of how the universe began. • The universe is 13.7 billion years old and appears to be expanding faster now than in the past. • The Hubble redshift is caused by the expansion of space, not the movement of galaxies. Chapter Review Question 1 Which type of galaxy is most common? A. barred galaxy B. dwarf elliptical C. irregular D. spiral Chapter Review Answer The answer is B. Dwarf elliptical galaxies can be over 9 million light-years across and contain trillions of stars. Chapter Review Question 2 What type of telescope is shown here? A. reflecting B. refracting C. radio D. laser Chapter Review Answer The answer is A. A reflecting telescope uses a mirror as an objective to reflect light to the focus. Chapter Review Question 3 According to the H-R diagram, which is the largest group of stars? A. giants B. white dwarfs C. supergiants D. main sequence Chapter Review Answer The answer is D. As long as the star’s gravity balances outward pressures, the star remains on the main sequence. Stars spend most of their life cycle on the main sequence. Chapter Review Question 4 What is produced when the core of a star collapses, and the outer portion of the star explodes? A. giant B. supernova C. dwarf D. blackhole Chapter Review Answer The answer is B. A supernova is a gigantic explosion in which the temperature in the collapsing core reaches 10 billion K and atomic nuclei are split into neutrons and protons. Chapter Review Question 5 Which is the most accepted theory of how the universe formed? A. oscillating B. collision C. steady state D. Big Bang Chapter Review Answer The answer is D. The Big Bang theory states that the universe started with a big bang, or explosion, and has been expanding ever since. Standardized Test Practice Question 1 How do stars change? Answer Once fusion begins, a star enters stellar equilibrium and becomes a main sequence star. When the hydrogen fuel is depleted, a star evolves into a giant star, or a supergiant. Standardized Test Practice Question 2 Which is a feature of the Sun that can reach 100 million K? A. CME B. solar flare C. prominence D. sunspot Standardized Test Practice Answer The answer is B. Temperatures within a solar flare can reach 100 million K. Standardized Test Practice Question 3 Which of the following is NOT a true statement about stars? A. Stars are composed of similar chemical elements. B. Stars differ in age. C. Stars differ in size. D. Stars are the same temperature. Standardized Test Practice Answer The answer is D. The temperature of a star changes as it progresses into new stage of its life cycle. Standardized Test Practice Question 4 What layer of the Sun gives us light? A. corona B. convection zone C. core D. photosphere Standardized Test Practice Answer The answer is D. The photosphere is the surface of the Sun and gives us light. Standardized Test Practice Question 5 What occurs in the core and radiation zone of the Sun’s interior? Standardized Test Practice Answer The core is the innermost layer and is where fusion occurs. The layer of the Sun just above the core is the radiation zone. In this layer, gases are completely ionized. This layer of the Sun is transparent to radiation. Help To advance to the next item or next page click on any of the following keys: mouse, space bar, enter, down or forward arrow. Click on this icon to return to the table of contents. Click on this icon to return to the previous slide. Click on this icon to move to the next slide. Click on this icon to open the resources file. Click on this icon to go to the end of the presentation. End of Chapter Resources File