1. Chapter 30 Table of Contents Section 1 Characterstics of Stars
Stars, Galaxies, and the Universe
Table of Contents
Section 1 Characterstics of Stars
Section 2 Stellar Evolution
Section 3 Star Groups
Section 4 The Big Bang Theory

2. Section 1 Characteristics of Stars
Chapter 30
Objectives
Describe how astronomers determine the compositions and temperature of stars.
Explain why stars appear to move in the sky.
Describe one way astronomers measure the distances to stars.
Explain the difference between absolute magnitude and apparent magnitude.

3. Chapter 30 Analyzing Starlight
Section 1 Characteristics of Stars
Chapter 30
Analyzing Starlight
star a large celestial body that is composed of gas and that emits light.
Nuclear fusion is the combination of light atomic nuclei to form heavier atomic nuclei
Astronomers learn about stars by analyzing the light that the stars emit.
Starlight passing through a spectrograph produces a display of colors and lines called a spectrum.

4. Analyzing Starlight, continued
Section 1 Characteristics of Stars
Chapter 30
Analyzing Starlight, continued
All stars have dark-line spectra, which are bands of color crossed by dark lines where the color is diminished.
A star’s dark-line spectrum reveals the star’s composition and temperature.
Stars are made up of different elements in the form of gases.
Because different elements absorb different wavelengths of light, scientists can determine the elements that make up a star by studying its spectrum.

5. The Compositions of Stars
Section 1 Characteristics of Stars
Chapter 30
The Compositions of Stars
Scientists have learned that stars are made up of the same elements that compose Earth.
The most common element in stars is hydrogen.
Helium is the second most common element in star.
Small quantities of carbon, oxygen, and nitrogen are also found in stars.

6. The Temperatures of Stars
Section 1 Characteristics of Stars
Chapter 30
The Temperatures of Stars
The temperature of most stars ranges from 2,800˚C to 24,000˚C.
Blue stars have average surface temperatures of 35,000˚C.
Yellow stars, such as the sun, have surface temperatures of about 5,500˚C.
Red stars have average surface temperatures of 3,000˚C.

7. The Sizes and Masses of Stars
Section 1 Characteristics of Stars
Chapter 30
The Sizes and Masses of Stars
Stars vary in size and mass.
Stars such as the sun are considered medium-sized stars. The sun has a diameter of 1,390,000 km.
Most stars visible from Earth are medium-sized stars.
Many stars also have about the same mass as the sun, however some stars may be more or less massive.

8. Chapter 30 Stellar Motion Apparent Motion
Section 1 Characteristics of Stars
Chapter 30
Stellar Motion
Apparent Motion
The apparent motion of stars is the motion visible to the unaided eye. Apparent motion is caused by the movement of Earth.
The rotation of Earth causes the apparent motion of stars sees as though the stars are moving counter-clockwise around the North Star.
Earth’s revolution around the sun causes the stars to appear to shift slightly to the west every night.

9. Stellar Motion, continued
Section 1 Characteristics of Stars
Chapter 30
Stellar Motion, continued
Reading Check
Why does Polaris appear to remain stationary in the night sky?

10. Stellar Motion, continued
Section 1 Characteristics of Stars
Chapter 30
Stellar Motion, continued
Reading Check
Why does Polaris appear to remain stationary in the night sky?
Polaris is almost exactly above the pole of Earth’s rotational axis, so Polaris moves only slightly around the pole during one rotation of Earth.

11. Stellar Motion, continued
Section 1 Characteristics of Stars
Chapter 30
Stellar Motion, continued
Circumpolar Stars
Some stars are always visible in the night sky. These stars never pass below the horizon.
In the Northern Hemisphere, the movement of these stars makes them appear to circle the North Star.
These circling stars are called circumpolar stars.

12. Stellar Motion, continued
Section 1 Characteristics of Stars
Chapter 30
Stellar Motion, continued
Actual Motion of Stars
Most stars have several types of actual motion.
Stars rotate on an axis.
Some stars may revolve around another star.
Stars either move away from or toward our solar system.

13. Stellar Motion, continued
Section 1 Characteristics of Stars
Chapter 30
Stellar Motion, continued
Actual Motion of Stars
Doppler effect an observed change in the frequency of a wave when the source or observer is moving
The spectrum of a star that is moving toward or away from Earth appears to shift, due to the Doppler effect.
Stars moving toward Earth are shifted slightly toward blue, which is called blue shift.
Stars moving away from Earth are shifted slightly toward red, which is called red shift.

14. Stellar Motion, continued
Section 1 Characteristics of Stars
Chapter 30
Stellar Motion, continued
The spectrum of a star that is moving toward or away from Earth appears to shift, as shown in the diagram below.

15. Chapter 30 Distances to Stars Section 1 Characteristics of Stars
light-year the distance that light travels in one year.
Distances between the stars and Earth are measured in light-years.
parallax an apparent shift in the position of an object when viewed from different locations.
For relatively close stars, scientists determine a star’s distance by measuring parallax.

16. Section 1 Characteristics of Stars
Chapter 30
Light-Year

17. Chapter 30 Stellar Brightness Section 1 Characteristics of Stars
Apparent magnitude the brightness of a star as seen from the Earth.
The apparent magnitude of a star depends on both how much light the star emits and how far the star is from Earth.
Absolute magnitude the brightness that a star would have at a distance of 32.6 light-years from Earth
The brighter a star is, the lower the number of its absolute magnitude.

18. Chapter 30 Stellar Brightness Section 1 Characteristics of Stars
The lower the number of the star on the scale shown on the diagram below, the brighter the star appears to observers.

19. Absolute and Apparent Motion
Section 1 Characteristics of Stars
Chapter 30
Absolute and Apparent Motion

20. Chapter 30 Objectives Describe how a protostar becomes a star.
Section 2 Stellar Evolution
Objectives
Describe how a protostar becomes a star.
Explain how a main-sequence star generates energy.
Describe the evolution of a star after its main-sequence stage.

21. Chapter 30 Classifying Stars Section 2 Stellar Evolution
Main sequence the location on the H-R diagram where most stars lie; it has a diagonal pattern from the lower right to the upper left.
One way scientists classify stars is by plotting the surface temperatures of stars against their luminosity. The H-R diagram is the graph that illustrates the resulting pattern.
Astronomers use the H-R diagram to describe the life cycles of stars. Most stars fall within a band that runs diagonally through the middle of the H-R diagram. These stars are main sequence stars.

22. Classifying Stars, continued
Chapter 30
Section 2 Stellar Evolution
Classifying Stars, continued
Main sequence the location on the H-R diagram where most stars lie; it has a diagonal pattern from the lower right to the upper left.
One way scientists classify stars is by plotting the surface temperatures of stars against their luminosity. The H-R diagram is the graph that illustrates the resulting pattern.
Astronomers use the H-R diagram to describe the life cycles of stars. Most stars fall within a band that runs diagonally through the middle of the H-R diagram. These stars are main sequence stars.

23. Classifying Stars, continued
Chapter 30
Section 2 Stellar Evolution
Classifying Stars, continued

24. Chapter 30 Star Formation Section 2 Stellar Evolution
nebula a large cloud of gas and dust in interstellar space; a region in space where stars are born.
A star beings in a nebula. When the nebula is compressed, some of the particles move close to eaother and are pulled together by gravity.
As described in Newton’s law of universal gravitation, as gravity pulls particles of the nebula closer together, the gravitational pull of the particles on each other increases.
As more particles come together, regions of dense matter begin to build up within the cloud.

25. Star Formation, continued
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Section 2 Stellar Evolution
Star Formation, continued
Protostars
As gravity makes dense regions within a nebula more compact, these regions spin and shrink and begin to form a flattened disk.The disk has a central concentration of matter called a protostar.
The protostar continues to contract and increase in temperature for several million years. Eventually the gas in the region becomes so hot that its electrons are stripped from their parent atoms.
The nuclei and free electrons move independently, and the gas is then considered a separate state of matter called plasma.

26. Star Formation, continued
Chapter 30
Section 2 Stellar Evolution
Star Formation, continued
The Birth of a Star
A protostar’s temperature continually increases until it reaches about 10,000,000°C.
At this temperature, nuclear fusion begins. Nuclear fusion is a process in which less-massive atomic nuclei combine to form more-massive nuclei. The process releases enormous amounts of energy.
The onset of nuclear fusion marks the birth of a star. Once this process begins, it can continue for billions of years.

27. Star Formation, continued
Chapter 30
Section 2 Stellar Evolution
Star Formation, continued
A Delicate Balancing Act
As gravity increases the pressure on the matter within the star, the rate of fusion increase.
In turn, the energy radiated from fusion reactions heats the gas inside the star.
The outward pressures of the radiation and the hot gas resist the inward pull of gravity.
This equilibrium makes the star stable in size.

28. Star Formation, continued
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Section 2 Stellar Evolution
Star Formation, continued
Reading Check
How does the pressure from fusion and hot gas interact with the force of gravity to maintain a star’s stability?

29. Star Formation, continued
Chapter 30
Section 2 Stellar Evolution
Star Formation, continued
Reading Check
How does the pressure from fusion and hot gas interact with the force of gravity to maintain a star’s stability?
The forces balance each other and keep the star in equilibrium. As gravity increases the pressure on the matter within a star, the rate of fusion increases. This increase in fusion causes a rise in gas pressure. As a result, the energy from the increased fusion and gas pressure generates outward pressure that balances the force of gravity.

30. The Main-Sequence Stage
Chapter 30
Section 2 Stellar Evolution
The Main-Sequence Stage
The second and longest stage in the life of a star is the main-sequence stage. During this stage, energy continues to be generated in the core of the star as hydrogen fuses into helium.
A star that has a mass about the same as the sun’s mass stays on the main sequence for about 10 billion years.
Scientists estimate that over a period of almost 5 billion years, the sun has converted only 5% of its original hydrogen nuclei into helium nuclei.

31. Leaving the Main Sequence
Chapter 30
Section 2 Stellar Evolution
Leaving the Main Sequence
Giant Stars
giant a very large and bright star whose hot core has used most of its hydrogen.
A star enters its third stage when almost all of the hydrogen atoms within its core have fused into helium atoms. billion years.
A star’s shell of gases grows cooler as it expands. As the gases in the outer shell become cooler, they begin to glow with a reddish color. These stars are known as giants.

32. Leaving the Main Sequence, continued
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Section 2 Stellar Evolution
Leaving the Main Sequence, continued
Supergiants
Main-sequence stars that are more massive than the sun will become larger than giants in their third stage.
These highly luminous stars are called supergiants. These stars appear along the top of the H-R diagram.

33. Leaving the Main Sequence, continued
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Section 2 Stellar Evolution
Leaving the Main Sequence, continued
Reading Check
Where are giants and supergiants found on the H-R diagram?

34. Leaving the Main Sequence, continued
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Section 2 Stellar Evolution
Leaving the Main Sequence, continued
Reading Check
Where are giants and supergiants found on the H-R diagram?
Giants and supergiants appear in the upper right part of the H-R diagram.

35. The Final Stages of a Sunlike Star
Chapter 30
Section 2 Stellar Evolution
The Final Stages of a Sunlike Star
Planetary Nebulas
As the star’s outer gases drift away, the remaining core heats these expanding gases.
The gases appear as a planetary nebula, a cloud of gas that forms around a sunlike star that is dying.

36. The Final Stages of a Sunlike Star, continued
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Section 2 Stellar Evolution
The Final Stages of a Sunlike Star, continued
White Dwarfs
As a planetary nebula disperses, gravity causes the remaining matter in the star to collapse inward.
The matter collapses until it cannot be pressed further together.
A hot, extremely dense core of matter - a white dwarf - is left. White dwarfs shine for billions of years before they cool completely.
The gases appear as a planetary nebula, a cloud of gas that forms around a sunlike star that is dying.

37. The Final Stages of a Sunlike Star, continued
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Section 2 Stellar Evolution
The Final Stages of a Sunlike Star, continued
Novas and Supernovas
nova a star that suddenly becomes brighter
Some white dwarfs revolve around red giants. When this happeneds, the gravity of the whit dwarf may capture gases from the red giant.
As these gases accumulate on the surface of the white dwarf, pressure begins to build up.
This pressure may cause large explosions. These explosions are called novas.

38. The Final Stages of a Sunlike Star, continued
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Section 2 Stellar Evolution
The Final Stages of a Sunlike Star, continued
Novas and Supernovas
A white dwarf may also become a supernova, which is a star that has such a tremedous explosion that it blows itself apart.
The explosions of supernovas completely destroy the white dwarf star and may destroy much of the red giant.

39. The Final Stages of Massive Stars
Chapter 30
Section 2 Stellar Evolution
The Final Stages of Massive Stars
Supernovas in Massive Stars
Massive stars become supernovas as part of their life cycle.
After the supergiant stage, the star collapses, producing such high temperatures that nuclear fusion begins again.
When nuclear fusion stops, the star’s core begins to collapse under its own gravity. This causes the outer layers to explode outward with tremendous force.

40. The Final Stages of Massive Stars, continued
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Section 2 Stellar Evolution
The Final Stages of Massive Stars, continued
Reading Check
What causes a supergiant star to explode as a supernova?

41. The Final Stages of Massive Stars, continued
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Section 2 Stellar Evolution
The Final Stages of Massive Stars, continued
Reading Check
What causes a supergiant star to explode as a supernova?
Giants and supergiants appear in the upper right part of the H-R diagram.

42. The Final Stages of Massive Stars, continued
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Section 2 Stellar Evolution
The Final Stages of Massive Stars, continued
Neutron Stars
neutron star a star that has collapsed under gravity to the point that the electrons and protons have smashed together to form neutrons
Stars more massive than the sun do not become white dwarfs.
After a star explodes as a supernova, the core may contract into a neutron star.

43. The Final Stages of Massive Stars, continued
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Section 2 Stellar Evolution
The Final Stages of Massive Stars, continued

44. Chapter 30
Section 2 Stellar Evolution
Types of Stars

45. The Final Stages of Massive Stars, continued
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Section 2 Stellar Evolution
The Final Stages of Massive Stars, continued
Pulsars
pulsar a rapidly spinning neutron star that emits pulses of radio and optical energy
Some neutron stars emit a beam of radio waves that sweeps across space and are detectable here on Earth.
These stars are called pulsars. For each pulse detected on Earth, we know that the star has rotated within that period.

46. The Final Stages of Massive Stars, continued
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Section 2 Stellar Evolution
The Final Stages of Massive Stars, continued
Black Holes
black hole an object so massive and dense that even light cannot escape its gravity
Some massive stars produce leftovers too massive to become a stable neutron star.
These stars contract, and the force of the contratction leaves a black hole.

47. Chapter 30
Section 3 Star Groups
Objectives
Describe the characteristics that identify a constellation.
Describe the three main types of galaxies.
Explain how a quasar differs from a typical galaxy.

48. Chapter 30 Constellations Dividing Up the Sky
Section 3 Star Groups
Constellations
Dividing Up the Sky
constellation one of 88 regions into which the skay has been divided in order to describe the locations of celestial objects; a group of stars organized in a recognizable pattern
In 1930, astronomers around the world agreed upon a standard set of 88 constellations.
You can use a map of the constellations to locate a particular star.

49. Constellations, continued
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Section 3 Star Groups
Constellations, continued
Naming Constellations
Many of the modern names we use for the constellations come from Latin.
Some constellations are named for real or imaginary animals, such as Ursa Major (the great bear) or ancient gods or legendary heroes, such as Hercules or Orion.

50. Constellations, continued
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Section 3 Star Groups
Constellations, continued
The Constellation Orion

51. Multiple-Star Systems
Chapter 30
Section 3 Star Groups
Multiple-Star Systems
Over half of all observed stars form multiple-star systems.
Binary stars are pairs of stars that revolve around each other and are held together by gravity. The center of mass, or barycenter, is somewhere between the two stars.
In star systems that have more than two stars, two stars may revolve rapidly around a common barycenter, while a third star revolves more slowly at a greater distance from the pair.

52. Multiple-Star Systems, continued
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Section 3 Star Groups
Multiple-Star Systems, continued
Reading Check
What percentage of stars are in multiple-star systems?

53. Multiple-Star Systems, continued
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Section 3 Star Groups
Multiple-Star Systems, continued
Reading Check
What percentage of stars are in multiple-star systems?
More than 50% of all stars are in multiple-star systems.

54. Chapter 30
Section 3 Star Groups
Star Clusters
Sometimes, nebulas collapse to form groups of hundreds or thousands of stars called clusters.
Globular clusters have a spherical shape and can contain up to 100,000 stars.
An open cluster is loosely shaped and rarely contains more than a few hundred stars.

55. Chapter 30
Section 3 Star Groups
Galaxies
galaxy a collection of stars, dust, and gas bound together by gravity
Galaxies are the major building blocks of the universe. Astronomers estimate that the universe contains hundreds of billions of galaxies.
A typical galaxy, such as the Milky Way, has a diameter of bout 100,000 light-years and may contain more than 200 billion stars.

56. Chapter 30 Galaxies, continued Distances to Galaxies
Section 3 Star Groups
Galaxies, continued
Distances to Galaxies
Giant stars called Cepheid variables brighten and fade in a regular pattern. Most Cepheids have regular cycles. The longer the cycle, the brighter the star’s absolute magnitude.
Scientists compare the Cepheid’s absolute magnitude and the Cepheid’s apparent magnitude to calculate the distance to the Cepheid variable.
This distance tells scientists the distance to the galaxy in which the Cepheid is located.

57. Chapter 30 Galaxies, continued Types of Galaxies Section 3 Star Groups
Galaxies are classified by shape into three main types.
A spiral galaxy has a nucleus of bright stars and flattened arms that spiral around the nucleus.
Elliptical galaxies have various shapes and are extremely bright in the center and do not have spiral arms.
An irregular galaxy has no particular shape, and is fairly rich in dust and gas.

58. Chapter 30
Section 3 Star Groups
Contents of Galaxies

59. Chapter 30
Section 3 Star Groups
The Milky Way
The galaxy in which we live, the Milky Way, is a spiral galaxy in which the sun is one of hundreds of billions of stars.
Two irregular galaxies, the Large Magellanic Cloud and Small Magellanic Cloud, are our closest neighbors.
These three galaxies are called the Local Group.

60. Chapter 30
Section 3 Star Groups
Quasars
quasar quasi-stellar radio source; a very luminous object that produces energy at a high rate.
Quasars appear as points of light, similar to stars.
Quasars are located in the centers of galaxies that are distant from Earth.
Quasars are among the most distant objects that have been observed from Earth.

61. Chapter 30
Section 4 The Big Bang Theory
Objectives
Explain how Hubble’s discoveries lead to an understanding that the universe is expanding.
Summarize the big bang theory.
List evidence for the big bang theory.

62. Hubble’s Observations
Chapter 30
Section 4 The Big Bang Theory
Hubble’s Observations
cosmology the study of the origin, properties, processes, and evolution of the universe
Cosmologists and astronomers can use the light given off by an entire galaxy to create the spectrum for that galaxy.
Edwin Hubble used galactic spectra to uncover new information about our universe.

63. Hubble’s Observations, continued
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Section 4 The Big Bang Theory
Hubble’s Observations, continued
Measuring Red Shifts
Hubble found that the spectra of galaxies, except for the few closest to Earth, were shifted toward the red end of the spectrum.
Hubble determined the speed at which the galaxies were moving away from Earth.
Hubble found that the most distant galaxies showed the greatest red shift and thus were moving away from Earth the fastest.

64. Hubble’s Observations, continued
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Section 4 The Big Bang Theory
Hubble’s Observations, continued
The Expanding Universe
Using Hubble’s observations, astronomers have been able to determine that the universe is expanding.
The expanding universe can be thought of as a raisin cake rising in the oven. If you were able to sit on one raisin, you would see all the other raisins moving away from you.
Similarly, galaxies in the universe are moving farther away from each other due to the expansion of the universe.

65. Chapter 30 The Big Bang Theory
Section 4 The Big Bang Theory
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 3 to 15 billion years ago exploded and began expanding in all directions
By the mid-20th century, almost all astronomers and cosmologists accepted the big bang theory.

66. The Big Bang Theory, continued
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Section 4 The Big Bang Theory
The Big Bang Theory, continued
Reading Check
What does the big bang theory tell us about the early universe?

67. The Big Bang Theory, continued
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Section 4 The Big Bang Theory
The Big Bang Theory, continued
Reading Check
What does the big bang theory tell us about the early universe?
All matter and energy in the early universe were compressed into a small volume at an extremely high temperature until the temperature cooled and all of the matter and energy were forced outward in all directions.

68. The Big Bang Theory, continued
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Section 4 The Big Bang Theory
The Big Bang Theory, continued
Cosmic Background Radiation
cosmic background radiation radiation uniformly detected from every direction in space; considered a remnant of the big bang.
Astronomers believe that cosmic background radiation formed shortly after the big bang.
The background radiation has cooled after the big bang, and is now about 270°C below zero.

69. The Big Bang Theory, continued
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Section 4 The Big Bang Theory
The Big Bang Theory, continued
Ripples in Space
Maps of cosmic background radiation over the whole sky show ripples.
These ripples are irregularities caused by small fluctuations in the distribution of matter in the early universe, and may indicate the first stages in the formation of the universe’s first galaxies.

70. The Big Bang Theory, continued
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Section 4 The Big Bang Theory
The Big Bang Theory, continued
Timeline of the Big Bang

71. Chapter 30
Section 4 The Big Bang Theory
Big Bang Theory

72. Chapter 30
Section 4 The Big Bang Theory
Universal Expansion

73. A Universe of Surprises
Chapter 30
Section 4 The Big Bang Theory
A Universe of Surprises
Dark Matter
Analysis of the ripples in the cosmic background radiation shows that the matter that humans, the planets, the stars and the matter between the stars makes up only 4% of the universe.
About 23% of the universe is made up of a type of matter that does not give off light but that has gravity. This type of matter is called dark matter.

74. A Universe of Surprises
Chapter 30
Section 4 The Big Bang Theory
A Universe of Surprises
Dark Energy
Most of the universe is made up of an unknown material called dark energy.
Scientists think that dark energy acts as a force that opposes gravity. Many scientists think that some form of undetectable dark energy is pushing galaxies apart.

75. Chapter 30
Maps In Action
Maps In Action
The Milky Way

76. Chapter 30
Stars, Galaxies, and the Universe
Brain Food Video Quiz

77. Chapter 30 Multiple Choice
Standardized Test Prep
Multiple Choice
1. What accounts for different stars being seen in the sky during different seasons of the year?
A. Stellar motion around Polaris
B. Earth’s rotation on its axis
C. Earth’s revolution around the sun
D. Position north or south of the equator

78. Multiple Choice, continued
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Standardized Test Prep
Multiple Choice, continued
1. What accounts for different stars being seen in the sky during different seasons of the year?
A. Stellar motion around Polaris
B. Earth’s rotation on its axis
C. Earth’s revolution around the sun
D. Position north or south of the equator

79. Multiple Choice, continued
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Standardized Test Prep
Multiple Choice, continued
2. How do stellar spectra provide evidence that stars are actually moving?
F. Dark line spectra reveal a star’s composition.
G. Long exposure photos show curved trails.
H. Light separates into different wavelengths.
I. Doppler shifts occur in the star’s spectrum.

80. Multiple Choice, continued
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Standardized Test Prep
Multiple Choice, continued
2. How do stellar spectra provide evidence that stars are actually moving?
F. Dark line spectra reveal a star’s composition.
G. Long exposure photos show curved trails.
H. Light separates into different wavelengths.
I. Doppler shifts occur in the star’s spectrum.

81. Multiple Choice, continued
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Standardized Test Prep
Multiple Choice, continued
3. What happens to main sequence stars when energy from fusion is no longer available?
A. They expand and become supergiants.
B. They collapse and become white dwarfs.
C. They switch to fission reactions.
D. They contract and turn into neutron stars.

82. Multiple Choice, continued
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Standardized Test Prep
Multiple Choice, continued
3. What happens to main sequence stars when energy from fusion is no longer available?
A. They expand and become supergiants.
B. They collapse and become white dwarfs.
C. They switch to fission reactions.
D. They contract and turn into neutron stars.

83. Multiple Choice, continued
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Standardized Test Prep
Multiple Choice, continued
4. Which type of star is most likely to be found on the main sequence?
F. a white dwarf
G. a red supergiant
H. a yellow star
I. a neutron star

84. Multiple Choice, continued
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Standardized Test Prep
Multiple Choice, continued
4. Which type of star is most likely to be found on the main sequence?
F. a white dwarf
G. a red supergiant
H. a yellow star
I. a neutron star

85. Multiple Choice, continued
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Standardized Test Prep
Multiple Choice, continued
5. Evidence for the big-bang theory is provided by
A. cosmic background radiation
B. apparent parallax shifts
C. differences in stellar luminosity
D. star patterns called constellations

86. Multiple Choice, continued
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Standardized Test Prep
Multiple Choice, continued
5. Evidence for the big-bang theory is provided by
A. cosmic background radiation
B. apparent parallax shifts
C. differences in stellar luminosity
D. star patterns called constellations

87. Chapter 30 Short Response
Standardized Test Prep
Short Response
6. What type of galaxy has no identifiable shape?

88. Short Response, continued
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Standardized Test Prep
Short Response, continued
6. What type of galaxy has no identifiable shape?
irregular galaxy

89. Chapter 30 Short Response
Standardized Test Prep
Short Response
7. What is the collective name for the Milky Way galaxy and a cluster of approximately 30 other galaxies located nearby?

90. Short Response, continued
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Standardized Test Prep
Short Response, continued
7. What is the collective name for the Milky Way galaxy and a cluster of approximately 30 other galaxies located nearby?
the local group

91. Chapter 30 Short Response
Standardized Test Prep
Short Response
8. What is the name for stars that seem to circle around Polaris and never dip below the horizon?

92. Short Response, continued
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Standardized Test Prep
Short Response, continued
8. What is the name for stars that seem to circle around Polaris and never dip below the horizon?
circumpolar stars

93. Chapter 30 Reading Skills Standardized Test Prep Geomagnetic Poles
Read the passage below. Then, answer questions 9–11.
Geomagnetic Poles
Today, we know that Copernicus was right - the stars are very far from Earth. In fact, stars are so distant that a new unit of length- the light-year - was created to measure their distance. A light-year is a unit of length equal to the distance that light travels through space in 1 year. Because the speed of light through space is about 300,000 km/ s, light travels approximately 9.46 trillion kilometers in one year.
Even after astronomers figured out that stars were far from Earth, the nature of the universe was hard to understand. Some astronomers thought that our galaxy, the Milky way, included every object in space. In the early 1920’s Edwin Hubble made one of the most important discoveries in astronomy. He discovered that the Andromeda galaxy, which is the closest major galaxy to our own, was past the edge of the milky Way. This fact confirmed the belief of many astronomers that the universe is larger than our galaxy.

94. Reading Skills, continued
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Standardized Test Prep
Reading Skills, continued
9. Why was Edwin Hubble’s discovery important?
A. Hubble’s discovery showed scientists that the universe was smaller than previously thought.
B. Hubble showed that the Andromeda galaxy was larger than the Milky Way galaxy.
C. Hubble's discovery showed scientists that the universe was larger than our own galaxy.
D. Hubble showed that all of the stars exist in two galaxies, the Andromeda and the Milky Way.

95. Reading Skills, continued
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Standardized Test Prep
Reading Skills, continued
9. Why was Edwin Hubble’s discovery important?
A. Hubble’s discovery showed scientists that the universe was smaller than previously thought.
B. Hubble showed that the Andromeda galaxy was larger than the Milky Way galaxy.
C. Hubble's discovery showed scientists that the universe was larger than our own galaxy.
D. Hubble showed that all of the stars exist in two galaxies, the Andromeda and the Milky Way.

96. Reading Skills, continued
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Standardized Test Prep
Reading Skills, continued
10. Because the sun and earth are close together, the distance between the sun and Earth is measured in light-minutes. A light-minute is the distance light travels in 1 minute. The sun is about 8 light-minutes from Earth. What is the approximate distance between the sun and Earth?
F. 2,400,000 km
G km
H. 144,000,000 km
I. 1,000,000,000 km

97. Reading Skills, continued
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Standardized Test Prep
Reading Skills, continued
10. Because the sun and earth are close together, the distance between the sun and Earth is measured in light-minutes. A light-minute is the distance light travels in 1 minute. The sun is about 8 light-minutes from Earth. What is the approximate distance between the sun and Earth?
F. 2,400,000 km
G km
H. 144,000,000 km
I. 1,000,000,000 km

98. Reading Skills, continued
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Standardized Test Prep
Reading Skills, continued
11. Why might scientists use light-years as a measurement of distance between stars?

99. Reading Skills, continued
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Standardized Test Prep
Reading Skills, continued
11. Why might scientists use light-years as a measurement of distance between stars?
Light-years can express vast distances in compact form. When expressing distance between stars, using light-years is easier and more efficient than using kilometers.

100. Interpreting Graphics
Chapter 30
Standardized Test Prep
Interpreting Graphics
The diagram below shows a group of stars called the
Big dipper moving over a period of 200,000 years. Use
this map to answer question 12.

101. Interpreting Graphics, continued
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Standardized Test Prep
Interpreting Graphics, continued
12. What does this series of drawings demonstrate about the individual stars in such a star group?

102. Interpreting Graphics, continued
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Interpreting Graphics, continued
12. What does this series of drawings demonstrate about the individual stars in such a star group?
Your answer should include the following:
The diagrams show that the individual stars move at different rates and in different directions from one another; constellations are arbitrary human distinctions; the stars within constellations move along individual paths, not as a group; the familiar patterns that stars form in the Earth’s sky change slowly over time as the stars that comprise the patterns move relative to each other; star movement may take thousands of years to become apparent.

103. Multiple Choice, continued
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Standardized Test Prep
Multiple Choice, continued
The table below shows data about several well-known
stars. Distance is given in light-years. Use this table to
answer questions 13 through 15.

104. Multiple Choice, continued
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Multiple Choice, continued
13. Which star has the brightest apparent magnitude as seen from Earth?
A. Rigel
B. Betelgeuse
C. Mintaka
D. Sirius

105. Multiple Choice, continued
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Standardized Test Prep
Multiple Choice, continued
13. Which star has the brightest apparent magnitude as seen from Earth?
A. Rigel
B. Betelgeuse
C. Mintaka
D. Sirius

106. Multiple Choice, continued
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Standardized Test Prep
Multiple Choice, continued
14. Which of these stars is the coolest?
F. Arcturus
G. Betelgeuse
H. Mintaka
I. Vega

107. Multiple Choice, continued
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Standardized Test Prep
Multiple Choice, continued
14. Which of these stars is the coolest?
F. Arcturus
G. Betelgeuse
H. Mintaka
I. Vega

108. Multiple Choice, continued
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Standardized Test Prep
Multiple Choice, continued
15. Which star most likely has a temperature that is similar to the temperature of our sun? Explain how you are able to determine this information.

109. Multiple Choice, continued
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Standardized Test Prep
Multiple Choice, continued
15. Which star most likely has a temperature that is similar to the temperature of our sun? Explain how you are able to determine this information.
Your answer should include the following:
The star in the table with the closest temperature to the sun is most likely Capella; a star’s temperature can be determined by its color. Stars that have similar colors share a common temperature range; Capella is a yellow star like the sun and thus it is the most likely to have a temperature similar to that of the sun.

110. Chapter 30
The Doppler Effect

111. Chapter 30
Apparent Magnitude

112. The Hertzsprung-Russell Diagram
Chapter 30
The Hertzsprung-Russell Diagram

113. Chapter 30
The Life Cycle of Stars

114. The Constellation Orion
Chapter 30
The Constellation Orion

115. Timeline of the Big Bang
Chapter 30
Timeline of the Big Bang

116. Chapter 30
The Milky Way