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Table of Contents

Chapter 15 Stars, Galaxies, and Universe. Table of Contents. Chapter Preview 15.1 Telescopes 15.2 Characteristics of Stars 15.3 Lives of Stars 15.4 Star Systems and Galaxies 15.5 The Expanding Universe. Chapter Preview Questions. 1. What is light?

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  1. Chapter 15 Stars, Galaxies, and Universe Table of Contents • Chapter Preview • 15.1 Telescopes • 15.2 Characteristics of Stars • 15.3 Lives of Stars • 15.4 Star Systems and Galaxies • 15.5 The Expanding Universe

  2. Chapter Preview Questions • 1. What is light? • a. electrical energy from the sun • b. matter that travels as waves • c. energy that travels in the form of waves • d. matter that allows us to see things

  3. Chapter Preview Questions • 1. What is light? • a. electrical energy from the sun • b. matter that travels as waves • c. energy that travels in the form of waves • d. matter that allows us to see things

  4. Chapter Preview Questions • 2. As the result of nuclear fusion, the sun gives off • a. mechanical and electrical energy. • b. chemical energy and sound. • c. electrical energy and light. • d. heat and light.

  5. Chapter Preview Questions • 2. As the result of nuclear fusion, the sun gives off • a. mechanical and electrical energy. • b. chemical energy and sound. • c. electrical energy and light. • d. heat and light.

  6. Chapter Preview Questions • 3. How many stars are in our solar system? • a. one • b. hundreds • c. thousands • d. millions

  7. Chapter Preview Questions • 3. How many stars are in our solar system? • a. one • b. hundreds • c. thousands • d. millions

  8. Chapter Preview Questions • 4. The planets and moons in our solar system are visible because they • a. emit their own light. • b. undergo nuclear fusion. • c. absorb light from the sun. • d. reflect light from the sun.

  9. Chapter Preview Questions • 4. The planets and moons in our solar system are visible because they • a. emit their own light. • b. undergo nuclear fusion. • c. absorb light from the sun. • d. reflect light from the sun.

  10. Suppose you shine the beam of a flashlight against the wall of a darkened room. You then measure the size of the circle made by the beam on the room. What do you think would happen to the size of the circle if you moved closer to the wall? Farther from the wall? Explain your answer. What is the structure and composition of the universe?

  11. End of Chapter Preview

  12. Section 1:Telescopes • What are the regions of the electromagnetic spectrum? • What are telescopes and how do they work? • Where are most large telescopes located?

  13. Electromagnetic radiation Visible light (Optical) Energy that travels through space in the form of waves All colors that can be seen Roy G. Biv – colors in the rainbow, through a prism Red, orange, yellow, green, blue, indigo, violet. Electromagnetic Radiation

  14. Types of radiation Radio waves Microwaves Infrared Visible light Ultraviolet X-rays Gamma rays Electromagnetic spectrum

  15. Electromagnetic Radiation • The electromagnetic spectrum includes the entire range of radio waves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays.

  16. Types of Telescopes • A refracting telescope uses convex lenses to focus light. A reflecting telescope has a curved mirror in place of an objective lens.

  17. Four Views of the Crab Nebula • Different type of telescopes collect electromagnetic radiation at different wavelengths. Astronomers are able to learn a great deal about the Crab Nebula by examining these different images. The images are shown at different scales.

  18. Types of Telescopes

  19. Links on Telescopes • Click the SciLinks button for links on telescopes.

  20. Telescopes • Click the Video button to watch a movie about telescopes.

  21. The Hubble Space Telescope • Click the Video button to watch a movie aboutthe Hubble Space Telescope.

  22. End of Section:Telescopes

  23. Section 2:Characteristicsof Stars • How are stars classified? • How do astronomers measure distances to the stars? • What is an H-R diagram and how do astronomers use it?

  24. Constellation Stars Imaginary pattern of stars Made up mostly of H (hydrogen) Produce energy through nuclear fusion Color shows temperature red – cool stars (3200°C) yellow – hotter stars (5500°C) blue – hottest stars (20,000°C) Classifying Stars

  25. Giant or supergiant Medium size Small size Very large stars Our sun’s size White dwarf – size of Earth Neutron stars – 20 km diameter. Size of Stars

  26. Star Size • Stars vary greatly in size. Giant stars are typically 10 to 100 times larger than the sun and more than 1,000 times the size of a white dwarf.

  27. Spectrograph 73% hydrogen (H) 25% helium (He) 2% other elements Breaks light into different colors Can determine gases in stars. Chemical Composition

  28. Star Spectrums • Astronomers can use line spectrums to identify the chemical elements in a star. Each element produces a characteristic pattern of spectral lines.

  29. Amount of light given off Depends on size and temperature Betelgeuse – cool and large, shines brightly Rigel – hot, brighter than Betelgeuse though smaller Brightness as seen from Earth Comparative. Brightness of Stars Apparent Brightness

  30. Absolute Brightness No matter where you measure the brightness, it has the same measurement Can compare brightness of all stars to each other. Brightness of Stars

  31. Astronomical Unit Light year 1 A.U. is the distance between Earth and the sun 1.44 X 108 kilometers (km). Measure distances between stars Distance light travels in one year 9.5 X 1012 kilometers (km). Measuring Distances to Stars

  32. The Hertzsprung-Russell Diagram • Astronomers use H-R diagrams to classify stars and to understand how stars change over time. Compare 2 stars – color, brightness, temp.

  33. H-R Diagram • On the H-R diagram: • Bottom X axis shows temperature, hottest on left, coolest on right • Top X axis shows color of stars, blue on left, red on right • Y axis shows brightness increasing

  34. Summary of Section • Use the following as a guide to write a summary of this section: • Stars are classified by ___________, _________, _______, ________, __________. Some stars appear brighter than others because ___________. Light years are used to measure distances between stars because ___________. The H-R diagram is used to _________.

  35. More on Types of Stars • Click the PHSchool.com button for an activityabout types of stars.

  36. End of Section:Characteristicsof Stars

  37. Section 3:Lives of Stars • How does a star form? • What determines how long a star will exist? • What happens to a star when it runs out of fuel?

  38. A Star Is Born • Nebula – large cloud of gas & dust, large volume • Gravity pulls gas & dust together • Forms protostar (no nuclear fusion) • When gas & dust are very dense & hot, nuclear fusion starts, a star is born • Stars with more mass use up fuel faster than smaller stars • Small stars – 200 billion years • Medium stars – 10 billion years (our sun) • Large stars – 10 million years

  39. The Lives of Stars • A star’s life history depends on its mass. After a star runs out of fuel, it becomes a white dwarf, a neutron star, or a black hole.

  40. The Lives of Stars • A star’s life history depends on its mass. After a star runs out of fuel, it becomes a white dwarf, a neutron star, or a black hole.

  41. Deaths of Stars • Hydrogen fuses to become helium and releases a lot of energy • When star uses up hydrogen helium can start fusing and creating new elements • Helium fuses in core to become carbon, oxygen • Massive stars produce heavier elements like iron • Stars without fuel become white dwarf, neutron star or black hole • Low mass star red giant planetary nebula white dwarf black dwarf

  42. Deaths of Stars • Supernova – explosion of supergiant • Explosion creates heavy elements, lead, gold • Explosion creates new stars with material from old star (recycling!) • Neutron star – remains of supergiant • Smaller, denser than white dwarfs • Pulsar – spinning neutron star • Gives off pulses of radiation in the form of radio waves • Black hole – gravity so strong nothing can escape • Cannot be detected directly

  43. The Lives of Stars Activity • Click the Active Art button to open a browser window and access Active Art about the lives of stars.

  44. Pulsar • Pulsars are spinning neutron stars that emit steady beams of radiation.

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