Chapter 14 The Stars: How much longer can the Sun sustain life on Earth?

Transcription

1 The Stars: How much longer can the Sun sustain life on Earth? 1. The energy source of stars is primarily associated with a. the reactions of atoms in the star corona. b. the reactions of nuclei in the star core. c. the reactions of atoms in the outer regions of the star. d. burning of elements until they become radioactive. e. burning of elements heavier than lead. 2. If scientists located a Dyson Sphere, they would find a. something made from a dismantled planet. b. a planet in orbit around our closest star. c. an energy source built to surround a planet. d. an object at the core of the Sun. e. the corona during a total eclipse. Ans: a 3. The solar wind a. extends into space as far as Mercury. b. consists of hydrogen and carbon particles. c. is a part of the Sun s atmospheric circulation. d. affects the magnetic fields of planets. e. is another term for the Sun s chromosphere. Ans: d 4. Which of the following can be said about large stars? a. Large stars have a longer lifetime than smaller stars. 226

2 b. Large stars have a shorter lifetime than smaller stars. c. Large star lifetime is about the same as that of smaller stars. d. The helium in the large star's core burns to produce hydrogen. e. Large stars are the source of oxygen in photosynthesis. 5. At this moment, the Sun is producing energy by burning a. plutonium. b. anthracite. c. hydrogen. d. helium. e.iron. Ans: c 6. The end products of fusion in the Sun's core are a. helium isotopes, protons, and gamma rays. b. hydrogen isotopes, photons, and infrared rays. c. helium ions, photons, and hydrogen isotopes. d. hydrogen ions, protons, and gamma rays. e. deuterium, photons, and gamma rays. Ans: a 7. Approximately how long does it take the energy of the Sun to be transferred from the stellar core to the photosphere? a. one light-year b. many thousands of years c. 24 hours d. one month e. eight minutes 227

3 8. Which of the following affect the life of a star? a. gravitational force b. mass c. temperature d. fusion processes e. all of the above Ans: e 9. From what part of the electromagnetic spectrum is most of the Sun s energy emitted? a. radio waves b.infrared waves c. visible light waves d. gamma rays e. microwaves Ans: c 10. Which of the following satellite observatories could not detect the presence of a black hole? a. Compton Gamma Ray Observatory (GRO) b. Chandra X-ray Observatory c. Hubble Space Telescope (HST) d. Space Infrared Telescope Facility (SIRTF) e. only a and b Ans: d 11. Differences in how a star appears in the sky are a function of a. the size of the star. b. how far away the star is from Earth. 228

4 c. the total energy emitted by the star. d. the star s apparent brightness. e. all of the above Ans: e Link To: The Variety of Stars 12. The Hertzsprung-Russell diagram is a graphical technique used in astronomy to compare a. the surface temperature versus the energy output of a star. b. the star s luminosity versus its distance from Earth. c. the absolute magnitude of the star versus the star s relative temperature. d. the distance the Sun is from the nearest red giant. e. the location of possible solar systems in the Milky Way. Ans: a 13. Where in the Milky Way galaxy would astronomers expect to find planetary systems other than our own? a. Dyson Sphere b. nebulae c. supernovas d. black hole e. Cepheid stars 14. Which of the following is not an endpoint of stellar evolution? a. white dwarf b. main sequence star c. pulsar d. black hole e. neutron star 229

5 15. Where were the heaviest chemical elements on Earth created? a. neutron stars b. black holes c. the Sun d. supernovae e. the asteroid belt Ans: d 16. If you were to observe a pulsar, what would you see? a. a blinking red glow b. intermittent radio waves c. a steady glow that oscillates among the stars d. the sudden brightening of a star e. the total eclipse of the Sun 17. What is Supernova 1987A likely to become? a. black hole b. pulsars c. main sequence star d. Cepheid variable e. solar wind 18. If the Hubble telescope detects an intensely bright region in the sky that lasts only a few days, it has probably found evidence of a a. white dwarf. b. supernova. 230

6 c. main sequence star. d. new galaxy. e. black hole. 19. Which of the following star variables would not be in an astronomer s data? a. wave length b. intensity c. sound d. position e. brightness Ans: c 20. Which of the following telescopes would have a collecting mirror? a. Chandra X-ray orbiting observatory telescope b. Hubble telescope c. Very Large Array telescope in New Mexico d. Hertzsprung-Russell telescope at Harvard e. all of the above 21. Which of the following is among the things scientists predict for Sun's demise? a. The burning of helium will produce a carbon ash core. b. The Sun will expand until it extends past the present orbit of Venus. c. The sun will emit more energy but appear to be cool. d. At different points in its final years, the Sun will become a red giant and a white dwarf. e. All of the above are true. Ans: e 231

7 22. Red giants can be described as a. huge planets that are surrounded by gases. b. large stars that emit a lot of energy but have cool surfaces. c. large stars that emit a lot of energy but have glowing, hot surfaces. d. stars that are in the hydrogen-burning stage of their lives. e. large planets with glowing iron oxide surfaces. 23. The starry night sky seen from Earth is a temporary phenomenon that has lasted about 15 billion years. 24. Some stars will burn forever. Ans: False 25. The Sun's peak output of energy is within the visible spectrum. 26. Record numbers of neutrinos from the Sun have been isolated at the solar neutrino laboratory in South Dakota. Ans: False 232

8 27. All objects with temperatures above absolute zero will radiate some form of electromagnetic waves. 28. Except for visible light and radio waves, the atmosphere of the Earth is opaque to most of the electromagnetic spectrum. 29. The absolute magnitude of a star is the brightness as seen from Earth, depending on the star s distance from Earth. Ans: False Link To: The Variety of Stars 30. The distance to stars greater than 500 light-years away is measured using Cepheid variable stars. Link To: The Variety of Stars 31. A main sequence star in the H-R diagram is in the hydrogen burning stage of its existence. 233

9 32. A star balances the forces of gravity against the high temperature and pressure of nuclear fires in the stellar core. 33. The degeneracy pressure of electrons is usually measured at the earliest stage of a star s existence. Ans: False 34. A star will start its existence as a white dwarf and end as a red giant. Ans: False 35. A neutron star is dense and small, compared to the Sun. 36. The supernova 1987A contradicted all the theories of stellar evolution proposed up to that time. Ans: False 37. What are the two factors that affect the behavior of every star? 234

10 Ans: Mass and age. Link To: The Variety of Stars 38. The iron in your blood was made during a. a chemical process that occurred during Earth's formation. b. the final moments in the life of a small star. c. fusion during our Sun's creation. d. fission reactions during the Big Bang. e. the nuclear burning of a very large star. Ans: e 39. If you were describing the structure of the Sun correctly, you would say that a. ten percent of the total volume of the Sun is the core. b. the Sun s outer region is a convection zone. c. the photosphere thins away from the Sun's surface. d. a gaseous chromosphere and corona are visible only during a solar eclipse. e. All of the above are true. Ans: e 40. Why do astronomers prefer orbiting telescopes over Earth-based telescopes? a. lower user costs and more research time options b. exciting space travel possible for observations c. wider range of electromagnetic wavelengths detected d. greater international cooperation e. more aesthetically pleasing Ans: c 235

11 41. It is impossible to extract energy from iron by fusion or fission. 42. Why are new stars made of hydrogen gas? Ans: Hydrogen gas is the simplest and the most common material in space. 43. What is the difference between apparent brightness and absolute brightness in star classification? Ans: Apparent brightness is relative brightness when viewed from Earth with distant stars appearing dimmer. Absolute brightness is a measure of stellar brightness from a standard distance. Link To: The Variety of Stars 44. Compare the process of hydrogen burning with helium burning in a star. Ans: After the hydrogen fuel in the core of a star is depleted, the star will contract under the force of gravity. At the same time the temperature will rise in the core until helium is fused to form carbon. Helium burning is the final stage in a star's life that produces energy. 45. Why do scientists believe that black holes exist, since black holes cannot be seen and none have ever been confirmed in space? Ans: Black holes give off a particular radiation signature; objects around the black hole behave in a particular manner. 236

12 46. From an observer s point of view, how would the birth of a star appear different from the death of a large star (supernovae)? Ans: These events are similar in that they both expel a shell of material although the supernova is more dramatic. These events are different in that the new star emits continuous light whereas the dying star fades to black. 47. From the perspective of Earth, how are neutron stars and pulsars the same and how are they different? Ans: They are actually the same object; pulsars are only neutron stars whose poles are pointing toward the Earth. 48. Why are imaginary space creatures often depicted as havingeyes larger than those of Earth dwellers? Compare the eyes of a Venusian with the eyes of a Plutonian. Science fiction writers and illustrators may be enlarging Ans: the eyes of extraterrestrials to indicate their need to collect more photons, similar in the theory explaining the large eyes of nocturnal animals. Following that logic, Venusian eyes would be smaller than those of the Plutonians. 49. What is the answer to the solar neutrino problem? Ans: Experiments before 2001, designed to measure the number of neutrinos given off by the Sun, had detected fewer neutrinos than expected. Scientists hypothesized that the ordinary electron neutrinos were converted to other types of neutrinos during their transit to Earth. The "lost" neutrinos were recently detected in an experiment comparing neutrino capture in pure water versus heavy water. Heavy water will only react with the electron neutrino. 237

13 Pure water will react with all kinds of neutrinos. One-third of the neutrinos are ordinary electron neutrinos; two-thirds have been converted. 50. List the events in the life of a Sun-like star in chronological order. Will the star becomes a supernova? Why or why not? Ans: It is a part of a concentration of mass in a cloud of gas and debris. It becomes a plasma made mostly of protons and electrons. Hydrogen is burned in the star s core. The star collapses temporarily. The star expands and becomes a red giant. The star shrinks to become a white dwarf. 51. What four aspects of photons are measured by astronomers and what instruments do the scientists use? Ans: Astronomers measure photon wavelength with spectroscopy; photon intensity with light meters; photon direction by recording two angles; and the variation of wavelength, intensity, and position over time. 52. Explain how the Northern Lights are formed. Ans: The Northern Lights, also called the Aurora Borealis, are flashing colored lights seen in the Earth s night sky at high northern latitudes when the ions forming the solar wind interact with the Earth's magnetic field in the outer reaches of the Earth s atmosphere. 53. How can the ashes of one stellar nuclear fire become the fuel for the next stellar nuclear fire? Ans: In medium size stars, hydrogen is burned in nuclear fusion reactions to form helium and, in the later stages, the helium ash is burned to produce carbon. The carbon itself cannot ignite in stars the size of our Sun. In very large stars, the pressure in the cores is so intense that the carbon can be changed by fusion into even larger nuclei like oxygen and silicon. 238

14 54. Why do larger stars have shorter life spans? Ans: Larger stars may have more hydrogen fuel to burn but have shorter life spans, when compared with small or average size stars. The reason is that large stars must burn hydrogen at rates many times greater than that of smaller stars to overcome the intense force of gravity caused by the star s massiveness. 55. How are naturally occurring elements heavier than iron formed in stellar processes? Ans: Elements heavier than iron are created when a very large star explodes in a supernova, sending out shockwaves. This raises the temperature and causes collisions of nuclei, which forms new elements. 56. How are Cepheid variables used to classify stars? Ans: The distance a star is from the Earth can be determined with triangulation (for nearby stars) or with Cepheid variables. The Cepheid variable stars are standards of comparison for stars greater than a few hundred light-years away using known values of energy output from the star and energy received by Earth. Distance is calculated from comparable brightness (magnitude). Link To: The Variety of Stars 57. What advantages might there be to living inside a Dyson Sphere? What would be the limitations future scientists must face before constructing a Dyson Sphere? Ans: A Dyson sphere would not only intercept and utilize all of a star s energy, it also could support a tremendous population. Such an immense structure would have an internal surface area comparable to more than 500 million Earth-like planets, and it would be uniformly heated in eternal daylight. 239

15 58. How are the original telescopes different from modern telescopes? How do the former improve upon the latter? Ans: Answers will vary but could include facts about early telescopes using only light whereas modern, non-optical telescopes use other sources of energy to see distant objects. Modern nonoptical telescopes can be used 24 hours a day, in good weather or bad. Modern optical telescopes have technological advances such as better glass grinding, computer operations, etc. 59. When pulsars were first detected, they were called LGM, which stood for Little Green Men. What characteristic of pulsars might have caused astronomers to give them this name? Ans: Answers will vary but should include reference to the regular pulse rate that appeared as if someone controlled the projection of energy. 60. If the Sun had not burned fairly evenly since the creation of the Earth, how would life on Earth be different? Ans: Answers will vary but could include plant and animal adaptations, different abundances of elements, and so forth. 61. If a new star were discovered, what characteristics would it have to have in order to be identified as a main sequence star? Ans: Medium size, temperature, color. 62. During ocean voyages, early sailors used a method called triangulation to determine the location of their ships. How is this same method used today by astronomers to determine the distance to certain neighboring stars? 240

16 Ans: By measuring the angle of sight to a given star from two points of known separation, we can determine the star s distance from us. 63. Evaluate the positive and negative aspects of using a star as an energy source as proposed by the construction of a Dyson Sphere. Ans: Positive: a source of energy lasting billions of years Negative: what to do with the solar wind particles and what happens if the star changes energy output even by 1-2%? 64. We don t often see stars in the daytime, but if you dug a hole deep enough could you see the stars from the bottom? Ans: Yes, but it would be a hole tens of miles deep. 65. If some one says to you, all stars are the same just tiny points of light, how might you convince them they have different temperatures (color) and different magnitudes (brightness). Ans: Answers will vary, however, the human eye is not good at discriminating color at low light levels, but a color photograph can illustrate different colors. As for brightness, light bulbs of the same wattage placed at different distances (or varying wattages placed at the same distances) can illustrate magnitude. Link To: The Variety of Stars 66. In the 1800s scientists knew that if the Sun was composed of conventional fuels (coal, oil, wood) it would have a burning life of only a few thousand years at best. How might this information impact the debate of how old is the Earth in that era? Ans: Either the Earth is only a few thousand years old or the Sun is using a different source of fuel one with a greater lifetime. 241

17 67. If the Earth had evolved around a different star a redder star that produced more frequencies in the infrared and microwave bands how might plant and animal development been altered to respond to these frequencies? Ans: Answers will vary but for sure if eyes developed they would have to be much larger to receive these longer frequencies. Plants would have evolved chlorophyll that responded to different wavelengths than that of green light. 68. What elements on the periodic table are the products of supernovae? Why would this be true? Ans: All elements heavier than iron are formed as a result of higher temperatures and pressures generated by larger stars when they undergo a catastrophic gravitational collapse. 69. How is it that optical telescopes are placed in orbit but radio telescopes are not? Ans: The visible spectrum frequencies are distorted and absorbed by the atmosphere but radio waves pass through relatively undisturbed. 242