1. Lesson 1 The View from Earth Lesson 2 The Sun and Other Stars
Chapter Introduction
Lesson 1 The View from Earth
Lesson 2 The Sun and Other Stars
Lesson 3 Evolution of Stars
Lesson 4 Galaxies and the Universe
Chapter Wrap-Up
Chapter Menu

2. Life Cycle of a Star (cont.)
Star-forming nebulae are cold, dense, and dark.
Photo courtesy of NASA/Corbis
Lesson 3-1

3. Life Cycle of a Star (cont.)
Gravity causes the densest parts to collapse, forming regions called protostars.
Over many thousands of years, the energy produced by protostars heats the gas and dust surrounding them.
Lesson 3-1

4. Life Cycle of a Star (cont.)
How do stars form?
Lesson 3-1

5. Life Cycle of a Star (cont.)
A star becomes a main-sequence star as soon as it begins to fuse hydrogen into helium.
Low-mass stars stay on the main sequence for billions of years, and high-mass stars are there for only a few million years.
Lesson 3-1

6. Life Cycle of a Star (cont.)
When a star’s hydrogen supply is nearly gone, the star leaves the main sequence and begins the next stage of its life cycle.
All stars form in the same way, but stars die in different ways, depending on their masses.
Massive stars eventually become red supergiants.
Lesson 3-1

7. Lesson 3-1

8. End of a Star
After helium in the cores of lower-mass stars is gone, the stars cast off their gases, exposing their cores.
The core eventually becomes a white dwarf, a hot, dense, slowly cooling sphere of carbon.
This is what is expected to happen to the Sun.
Lesson 3-2

9. The Sun will remain on the main sequence for 5 billion more years.
Lesson 3-2

10. When the Sun becomes a red giant for the second time, it will probably absorb Earth and push Mars and Jupiter outward.
Lesson 3-2

11. When the Sun becomes a white dwarf, the solar system will be a cold, dark place.
Lesson 3-2

12. End of a Star (cont.)
Very massive stars can explode in a supernova, which destroys the star.
Iron in the core does not fuse and the core collapses quickly under the force of gravity.
The normal space within atoms is eliminated, leaving a dense core of neutrons, or a neutron star.
Lesson 3-2

13. End of a Star (cont.)
For the most massive stars, atomic forces holding neutrons together are not strong enough to overcome so much mass in such a small volume. Gravity is too strong, and the matter crushes into a black hole.
A black hole is an object whose gravity is so great that no light can escape.
Lesson 3-2

14. End of a Star (cont.)
How does a star’s mass determine if it will become a white dwarf, a neutron star, or a black hole?
Lesson 3-2

15. Recycling Matter
When a star becomes a white dwarf, it casts off hydrogen and helium gases in its outer layers.
The expanding, cast-off matter of a white dwarf is a planetary nebula.
During a supernova, a massive star comes apart sending a shock wave into space.
Lesson 3-3

16. Recycling Matter (cont.)
The expanding cloud of dust and gas is called a supernova remnant.
Gravity causes recycled gases and other matter to clump together in nebulae and form new stars and planets.
Lesson 3-3

17. Recycling Matter (cont.)
How do stars recycle matter?
Lesson 3-3

18. Iron is formed in the cores of the most massive stars.
Lesson 3 - VS

19. The Sun will become a red giant in about 5 billion years.
Matter is recycled in supernovae.
Lesson 3 - VS

20. What term refers to clouds of gas and dust where stars form?
A. white dwarf
B. supernova
C. nebula
D. black hole
Lesson 3 – LR1

21. What type of star is a hot, dense, slowly cooling sphere of carbon?
A. neutron star
B. red giant
C. supernova
D. white dwarf
Lesson 3 – LR2

22. Which of these is an object whose gravity is so great that no light can escape?
A. white dwarf
B. supernova
C. nebula
D. black hole
Lesson 3 – LR3

23. 5. The more matter a star contains, the longer it is able to shine.
Do you agree or disagree?
5. The more matter a star contains, the longer it is able to shine.
6. Gravity plays an important role in the formation of stars.
Lesson 3 - Now

24. Lesson 4 Reading Guide - KC
Galaxies and the Universe
What are the major types of galaxies?
What is the Milky Way, and how is it related to the solar system?
What is the Big Bang theory?
Lesson 4 Reading Guide - KC

25. Lesson 4 Reading Guide - Vocab
Galaxies and the Universe
galaxy
dark matter
Big Bang theory
Doppler shift
Lesson 4 Reading Guide - Vocab

26. Galaxies Galaxies are huge collections of stars. galaxy
from Greek galactos, means “milk”
Lesson 4-1

27. Galaxies (cont.) Gravity holds stars and galaxies together.
When astronomers examine how galaxies rotate and gravitationally interact, they find that most of the matter in galaxies is invisible.
Matter that emits no light at any wavelength is dark matter.
Lesson 4-1

28. Types of Galaxies: Spiral Galaxies
Spiral arms of stars, gas, and dust extend from central disk.
Spiral galaxies have a central bulge.
A spherical halo surrounds the disk.
NASA/JPL-Caltech/S. Willner (Harvard-Smithsonian Center for Astrophysics)
Lesson 4-1

29. Types of Galaxies: Elliptical Galaxies
Elliptical galaxies have a spherical or elliptical shape and no internal structure.
They contain more older stars than spiral galaxies, and may have formed as spiral galaxies merged.
JPL/NASA
Lesson 4-1

30. Types of Galaxies: Irregular Galaxies
Irregular galaxies are oddly shaped and contain many young stars.
Local Group Galaxies Survey Team, NOAO, AURA, NSF
Lesson 4-1

31. Galaxies (cont.)
What are the major types of galaxies?
Lesson 4-1

32. The Milky Way
The solar system is in the Milky Way, a spiral galaxy that contains gas, dust, and almost 200 billion stars.
The Milky Way is a member of the Local Group, a cluster of about 30 galaxies.
Lesson 4-2

33. Lesson 4-2

34. The Milky Way (cont.)
Where is Earth in the Milky Way?
Lesson 4-2

35. The Big Bang Theory
According to the Big Bang theory, the universe began from one point billions of years ago and has been expanding ever since.
What is the Big Bang theory?
Lesson 4-3

36. The Big Bang Theory (cont.)
Most scientists agree that the universe is billion years old.
Scientists observe how space stretches by measuring the speed at which galaxies move away from the Earth.
Lesson 4-3

37. The Big Bang Theory (cont.)
When light travels away from you, its wavelength stretches out, shifting to the red end of the electromagnetic spectrum.
The shift to a different wavelength is called the Doppler shift.
Lesson 4-3

38. Doppler Shift
Lesson 4-3

39. The Sun is one of billions of stars in the Milky Way.
By studying interacting galaxies, scientists have determined that most mass in the universe is dark matter.
The Sun is one of billions of stars in the Milky Way.
Lesson 4 - VS

40. When an object moves away, its light stretches out, just as a siren’s sound waves stretch out as the siren moves away.
Lesson 4 - VS

41. What term refers to matter that emits no light at any wavelength?
A. clusters
B. dark matter
C. H-R matter
D. light matter
Lesson 4 – LR1

42. The Milky Way is a member of the Local Group which is a cluster of about how many galaxies?
D. 1 billion
Lesson 4 – LR2

43. Approximately what is the age of the universe?
A. 1-2 million years
B million years
C. 4-5 billion years
D billion years
Lesson 4 – LR3

44. 7. Most of the mass in the universe is in stars.
Do you agree or disagree?
7. Most of the mass in the universe is in stars.
8. The Big Bang theory is an explanation of the beginning of the universe.
Lesson 4 - Now

45. Interactive Concept Map Chapter Review Standardized Test Practice
Key Concept Summary
Interactive Concept Map
Chapter Review
Standardized Test Practice
Chapter Review Menu

46. The universe is made up of stars, gas, and dust, as well as invisible dark matter. Material in the universe is pulled by gravity into galaxies, including our own Milky Way galaxy.
The BIG Idea

47. Lesson 1: The View from Earth
The sky is divided into 88 constellations.
Astronomers learn about the energy, distance, temperature, and composition of stars by studying their light.
Astronomers measure distances in space in astrological units and in light-years. They measure star brightness as apparent magnitude and as luminosity.
Key Concepts 1

48. Lesson 2: The Sun and Other Stars
Stars shine because of nuclear fusion in their cores.
Stars have a layered structure—they conduct energy through their radiative zones and their convection zones and release the energy at their photospheres.
Sunspots, prominences, flares, and coronal mass ejections are temporary phenomena on the Sun.
Astronomers classify stars by their temperatures and luminosities.
Key Concepts 2

49. Lesson 3: Evolution of Stars
Stars are born in clouds of gas and dust called nebulae.
What happens to a star when it leaves the main sequence depends on its mass.
Matter is recycled in the planetary nebulae of white dwarfs and the remnants of supernovae.
Key Concepts 3

50. Lesson 4: Galaxies and the Universe
The three major types of galaxies are spiral, elliptical, and irregular.
The Milky Way is the spiral galaxy that contains the solar system.
The Big Bang theory explains the origin of the universe.
Key Concepts 4

51. Which of these describes the average distance between Earth and the Sun?
A. astronomical unit
B. Doppler shift
C. light-year
D. solar distance
Chapter Review – MC1

52. The true brightness of an object can also be referred to as which of these?
A. apparent magnitude
B. astronomical unit
C. luminosity
D. spectrum
Chapter Review – MC2

53. Which term refers to the apparent surface of a star?
A. chromosphere
B. convection zone
C. corona
D. photosphere
Chapter Review – MC3

54. Which is an enormous explosion that destroys a star?
A. supernova
B. nebula
C. Hertzsprung-Russell event
D. Doppler shift
Chapter Review – MC4

55. The universe began from one point billions of years ago and has been expanding ever since, according to which of these?
A. Big Bang theory
B. Doppler shift
C. H-R diagram
D. law of magnitude
Chapter Review – MC5

56. Which of these refers to the distance light travels in one year?
A. astronomical unit
B. light-year
C. solar magnitude
D. 2 trillion km
Chapter Review – STP1

57. Which of these spreads light into different wavelengths?
A. telescope
B. spectroscope
C. photosphere
D. dark matter
Chapter Review – STP2

58. Which of these is the shell of cooler hydrogen above a star’s core?
A. radiative zone
B. photosphere
C. corona
D. convection zone
Chapter Review – STP3

59. Which of these is the dense core of matter left from a supernova?
A. white dwarf
B. neutron star
C. nebula
D. black hole
Chapter Review – STP4

60. Which term refers to huge collections of stars?
A. galaxies
B. dark matter
C. clusters
D. astronomical units
Chapter Review – STP5