Stars, Galaxies, and the Universe


Published on

Published in: Education, Technology
1 Like
  • Be the first to comment

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Stars, Galaxies, and the Universe

  1. 1. Warmup  What are stars made of?  How do stars differ from one another?  Do stars move?
  2. 2. Stars, Galaxies, and the Universe Earth Science: Book J, Chapter 2
  3. 3. Section 1: Stars By the end of this section, you should be able to:       Describe how color indicates the temperature of a star Explain how a scientist can identify a star’s composition Describe how scientists classify stars. Compare absolute magnitude with apparent magnitude. Identify how astronomers measure distances from Earth to stars. Describe the difference between the apparent motion and the actual motion of stars.
  4. 4. Composition of Stars  Because a blue flame is hotter than a yellow or red flame, we can conclude that blue stars are hotter than yellow or red stars.
  5. 5. Composition of Stars  A star is made of different elements in the form of gases.  The gases in the atmosphere of a star absorb different wavelengths of light radiating from the star, depending on which elements make up the gases.
  6. 6. Composition of Stars  The light from a star indicates which elements make up that star.  A prism breaks white light into a rainbow of colors called a spectrum.  An instrument called a spectrograph is used to break a star’s light into a spectrum. The spectrum of a star will vary depending on which elements are present.
  7. 7. Composition of Stars  Emission lines are lines made when certain wavelengths of light, or colors, are given off by hot gasses.  Each element produces a unique set of emission lines, which allows them to be used to identify the elements in a star.
  8. 8. Emission Lines of Elements
  9. 9. Fingerprinting Cars  Police use spectrographs to “fingerprint” cars. Car makers put trace elements in the paint of cars. Each make of car has a special paint and thus its own combination of trace elements.  When a car is in a hit-and-run accident, police can ID the make of the car by the paint left behind.
  10. 10. Composition of Stars  A star’s spectrum is made of dark emission lines. A star’s atmosphere absorbs certain colors of light, which causes black lines to appear.  Because a star’s atmosphere absorbs some colors of light, the spectrum of a star is called an absorption spectrum. It can be used to identify some of the elements in a star’s atmosphere.
  11. 11. Continuous vs. Absorption Spectrum
  12. 12. Classifying Stars  Stars are now classified by how hot they are.  The brightest star, Sirius, has a magnitude of -1.4. The dimmest star that can be seen with a microscope has a magnitude of 29.
  13. 13. Magnitude of Stars in Big Dipper
  14. 14. Classifying Stars  The brightness of a light or star is called apparent magnitude.  Absolute magnitude is the actual brightness of a star.
  15. 15. Distance to the Stars  Because stars are so far away, astronomers use light-years to measure the distances from Earth to the stars.  A light year is the distance that light travels in a year.
  16. 16. Quick Lab – Not All Thumbs p.37
  17. 17. Distance to the Stars  Parallax is the apparent shift in the position of an object when viewed from different locations. Measuring parallax enables scientists to calculate the distance between a star and the Earth.
  18. 18. Motions of Stars  If you look at the night sky long enough, the stars also appear to move.  The apparent motion of the sun and stars in our sky is due to Earth’s rotation. But each star is also moving in space. Their actual movements, however, are difficult to see.
  19. 19. Apparent Motion of Stars
  20. 20. Actual Motion of Stars
  21. 21. Section 1 Review p.39 #3-10
  22. 22. Warmup
  23. 23. Section 2: Life Cycle of Stars By the end of this section, you should be able to:    Describe different types of stars. Describe the quantities that are plotted in the H-R diagram. Explain how stars at different stages in their life cycle appear on the H-R diagram.
  24. 24. Beginning and End of Stars  A star enters the first stage of its life cycle as a ball of gas and dust.  Gravity pulls the gas and dust together, and hydrogen changes to helium in a process called nuclear fusion.
  25. 25. Beginning and End of Stars  Stars usually lose material slowly, but sometimes they can lose material in a big explosion. Much of a star’s material returns to space, where it sometimes forms new stars.
  26. 26. Different Types of Stars  Stars can be classified by their size, mass, brightness, color, temperature, spectrum, and age. A star’s classification can change as it ages.
  27. 27. Different Types of Stars  After a star forms, it enters the second and longest stage of its life cycle known as the main sequence.  During this stage, energy is generated in the core as hydrogen atoms fuse into helium atoms.
  28. 28. Different Types of Stars  After the main-sequence stage, a star can enter the third stage of its life cycle when it can become a red giant.  As the center of the star shrinks, the atmosphere of the star grows very large and cools to form a red giant or a red supergiant.
  29. 29. How Giant?  Red giants can be 10 or more times bigger than the sun.  Supergiants are at least 100 times bigger than the sun.
  30. 30. Different Types of Stars  In the final stages of its life cycle, a star with the same mass as the sun or smaller can become a white dwarf.  A white dwarf can no longer generate energy through nuclear fusion. They can shine for billions of years before they cool completely.
  31. 31. A Tool for Studying Stars  The Hertzprung-Russell diagram is a graph that shows the relationship between a star’s surface temperature and absolute magnitude.  The diagonal pattern on the H-R diagram where most stars lie is called the main sequence.
  32. 32. H-R Diagram
  33. 33. When Stars Get Old  A supernova is a gigantic explosion in which a massive blue star collapses.  A star that has collapsed under gravity to the point at which all of its particles are neutrons is called a neutron star.
  34. 34. When Stars Get Old  If a neutron star is spinning, it is called a pulsar.  Sometimes the leftovers of a supernova are so massive that they collapse to form a black hole.  A black hole is an object that is so massive that even light cannot escape its gravity.
  35. 35. Section 2 Review p.45 #4-12
  36. 36. Warmup  Describe the evidence that indicates that the galaxy is rotating.  What other objects have you seen look similar to a spiral galaxy? Do they rotate?
  37. 37. Section 3: Galaxies By the end of this section, you should be able to:    Identify three types of galaxies. Describe the contents and characteristics of galaxies. Explain why looking at distant galaxies reveals what young galaxies looked like.
  38. 38. Types of Galaxies  A galaxy is a collection of stars, dust, and gas held together by gravity.
  39. 39. Types of Galaxies  Spiral galaxies have a bulge at the center and spiral arms.  Astronomers think that our solar system is in a spiral galaxy.
  40. 40. Types of Galaxies  About one-third of all galaxies are simply massive blobs of stars. These are called elliptical galaxies.
  41. 41. Types of Galaxies  Galaxies that do not fit into any other class are called irregular galaxies.
  42. 42. What are Galaxies Made Up Of?  A large cloud of gas and dust in interstellar space is called a nebula.
  43. 43. What are Galaxies Made Up Of?  A globular cluster is a tight group of stars that looks like a ball and contains up to 1 million stars.
  44. 44. What are Galaxies Made Up Of?  An open cluster is a group of stars that are close together relative to surrounding stars.
  45. 45. Origins of Galaxies  Because it takes light time to travel through space, looking at distant galaxies reveals what early galaxies looked like.
  46. 46. Origins of Galaxies  A very luminous, star-like object that generates energy at a high rate is called a quasar. Some scientists think that quasars may be the core of young galaxies that are in the process of forming.
  47. 47. Section 3 Review p.49 #2-6
  48. 48. Warmup  The first image represents the initial explosion of the big bang, and the following images represent the expansion of the universe and the formation of the galaxies.  Describe the differences between the images.
  49. 49. Section 4: Formation of the Universe By the end of this section, you should be able to:      Describe the big bang theory. Explain evidence used to support the big bang theory. Describe the structure of the universe. Describe two ways scientists calculate the age of the universe. Explain what will happen if the universe expands forever.
  50. 50. Universal Expansion  Cosmology is the study of the origin, properties, processes, and evolution of the universe.  To understand how the universe formed, scientists study the movement of galaxies.
  51. 51. Universal Expansion  The universe, like the rising raisin bread dough, is expanding. Think of the raisins in the dough as galaxies. As the universe expands, the galaxies move farther apart.
  52. 52. The Big Bang Theory  The theory that the universe began with a tremendous explosion is called the big bang theory.
  53. 53. The Big Bang Theory  In 1964, two scientists using a huge antenna accidentally found radiation coming from all directions in space. One explanation for this radiation is that it is cosmic background radiation left over from the big bang.
  54. 54. Structure of the Universe
  55. 55. How Old is the Universe?  Scientist use two methods to estimate the age of the universe.  By measuring the distance between Earth and various galaxies, scientists can predict the rate of expansion and calculate the age of the universe.  Because the universe must at least be as old as the oldest stars it contains, the ages of the stars provide a clue to the age of the universe.
  56. 56. A Forever Expanding Universe  The expansion of the universe depends on the amount of matter it contains.  A large enough quantity of matter would cause gravity to stop the expansion. The universe could start collapsing.
  57. 57. A Forever Expanding Universe  Scientists now think that there may not be enough matter in the universe, so the universe would continue to expand forever and become cold and dark as all the stars die.
  58. 58. Section 4 Review p.53 #2-8