1. Table of Contents Chapter 15 Stars, Galaxies, and Universe
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. What is the structure and composition of the universe?
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.

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.

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

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 Type of Radiation Name and location of telescope
What has been found?
Radio waves ,
Infrared
Microwave
X-Ray
Visible

19. Ultraviolet
GALEX, space
Gamma

20. Click the SciLinks button for links on telescopes.

21. Click the Video button to watch a movie about telescopes.

22. The Hubble Space Telescope
Click the Video button to watch a movie about the Hubble Space Telescope.

23. End of Section: Telescopes

24. Section 2: Characteristics of 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?

25. Classifying Stars 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)

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

28. 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.

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

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

31. Brightness of Stars
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.
Apparent Brightness

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

33. Measuring Distances to Stars
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).

34. 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.

36. 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

37. 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 _________.

38. Click the PHSchool.com button for an activity about types of stars.
More on Types of Stars
Click the PHSchool.com button for an activity about types of stars.

39. End of Section: Characteristics of Stars

40. 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?

43. 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

45. 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.

46. 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.

47. 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

48. 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

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

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

51. Black Holes
The remains of the most massive stars collapse into black holes. Here, a black hole is shown pulling matter from a companion star.
Gas near a black hole pulled inward, x-rays observed, gravitational effect on nearby stars

52. End of Section: Lives of Stars

53. Section 4: Star Systems and Galaxies
What is a star system?
What are the major types of galaxies?
How do astronomers describe the scale of the universe?

54. Star Systems and Clusters
Our galaxy = Milky Way
Star systems – two or more stars together
Binary stars – two stars or double stars
One star brighter, more massive
Dimmer star’s gravity causes “wobble”
Eclipsing binary – one star blocks light from another star
Triple stars – 3 stars together
Found at least 500 other planets that revolve around stars- called exoplanets.
Found by “wobble” of star.

55. Star Clusters
Large groupings of stars
Formed from same nebula at about same time
Open clusters – disorganized appearance, a few thousand stars
Globular clusters – large groupings of older stars, more than a million stars.

56. Galaxies
Huge group of single stars, star systems, star clusters, dust and gas
Many have black holes in center
Billions of stars in galaxy
Billions of galaxies in universe
Quasar – distant, very bright young galaxy with black hole in center.

57. Types of Galaxies
Astronomers classify most galaxies into three main categories: spiral, elliptical, and irregular.

58. Types of Galaxies
Spiral – bulge in middle, arms spiral outward
Spiral arms contain new stars, gas, dust
New stars formed in spiral arms
Elliptical – round or oval shape, billions of stars, little gas or dust, therefore old stars
Irregular – smaller than other galaxies
Young stars, lots of gas and dust
Located close to larger galaxies.

59. Structure of the Milky Way
Our solar system is located in a spiral galaxy called the Milky Way. From the side, the Milky Way appears to be a narrow disk with a bulge in the middle. The galaxy’s spiral structure is visible only from above or below.
Center is 25,000 light years away from Earth

60. Scale of the Universe
Universe
Scientific Notation
All of space and everything in it
Objects are very large and very far away
Uses powers of ten to write very large or very small numbers
One light year = 9,500,000,000,000,000 meters. Written as 9.5 X 1015m, 9.5X1012 km.

61. Scientific Notation
The bright star Deneb is about 3,230 light-years from Earth. To express this number in scientific notation, first insert a decimal point in the original number so that you have a number between one and ten. In this case, the number is 3.23.
To determine the power of 10, count the number of places that the decimal point moved. Here the decimal point moved three places.
3,230 light-years = 3.23 x 103 light-years.

62. Click the SciLinks button for links on galaxies.

63. End of Section: Star Systems and Galaxies
ALL CLASSES: Draw a triple Venn Diagram of the 3 types of galaxies.
Answer questions 1a,b,c, 2a,b,c, 3a,b,c, and 4 on P. 621.
End of Section: Star Systems and Galaxies

64. Section 5: The Expanding Universe
What is the big bang theory?
How did the solar system form?
What do astronomers predict about the future of the universe?

65. Retreating Galaxies
All of the distant galaxies astronomers have observed are moving rapidly away from our galaxy and from each other.

66. Speeding Galaxies
Use the graph to answer the questions about moving clusters of galaxies.

67. Speeding Galaxies Reading Graphs:
How far away is the Bootes cluster? How fast is it moving?
About 2.5 billion light-years; about 39,000 km/sec

68. Speeding Galaxies Reading Graphs:
Which galaxy is moving away the fastest? Which galaxy is closest to Earth?
Hydra; Virgo

69. Speeding Galaxies Drawing Conclusions:
How are the distance and speed of a galaxy related?
The greater the distance from Earth, the greater the speed of the galaxy.

70. Speeding Galaxies Predicting:
Predict the speed of a galaxy that is 5 billion light-years from Earth.
Its speed would be about 80,000 km/s.

71. Moving Galaxies
The galaxies in the universe are like the raisins in rising bread dough.

72. Formation of the Solar System
The solar system formed from a collapsing cloud of gas and dust.

73. Links on the Expanding Universe
Click the SciLinks button for links on the expanding universe.

74. End of Section: The Expanding Universe

75. QuickTake Quiz
Click to start quiz.