Astronomy 132 - Stars, Galaxies and Cosmology Exam 3 Please PRINT full name Also, please sign the honor code: I have neither given nor have I received help on this exam The following exam is intended to take no more than 60 minutes, although 75 minutes is allotted for it. For each question, pick the letter that best answers the question. When finished, turn in the complete exam! If there are problems regarding particular questions, I will deal with them upon my return. Star Formation For questions 1-4, read the complete list of questions before answering. They relate to the sequence of star formation... 1. The first stage of the star formation process, according to the "Standard Model", occurs when: a. regions within a giant molecular cloud begin to collapse b. stars are undergoing thermonuclear reactions in their cores c. electrons are compressed into protons d. Hydrogen is being converted into Helium inside the star e. Iron is formed in the core of a star 2. The next stage of the star formation process, according to the "Standard Model", occurs when: a. a circumstellar disk forms around the newly forming star b. thermonuclear energy is produced from the conversion of Hydrogen into Helium c. planets form and produce energy through nuclear processes 3. The following stage of the star formation process, according to the "Standard Model", occurs when: a. regions within a giant molecular cloud begin to collapse b. an outflow of material along the rotation axis develops c. planets form and produce energy through nuclear processes d. all of the above 4. The final stage of the star formation process, when we can say that a star is born, according to the "Standard Model", occurs when: a. the disk begins to dissipate b. the star begins nuclear fusion in its core c. planets may form in the disk 1
The Sun as a Star 5. Thermonuclear reactions in the Sun a. occur in the core b. occur in the intermediate interior c. occur when temperatures reach >10 7 K 6. The actual mechanism(s) responsible for most energy produced by the Sun is/are: a. gravitational processes b. nuclear processes c. chemical processes 7. In the late 1800s/early 1900s, evidence that the Sun must be older than 100 million years came from: a. Darwin's theory of evolution b. the radioactive dating of rocks c. ages of stars d. a and b e. b and c 8. The individual constituents of the Helium nucleus a. have more mass than does the Helium nucleus b. have less mass than does the Helium nucleus c. are made of different chemical elements d. are composed of electrons 9. To overcome the repulsion between protons, and ensure that enough reactions occur, the following is/are required in the core of a star for thermonuclear reactions: a. high temperature and low density b. high temperature and high density c. low temperature and low density d. low temperature and high density 10. Which of the following occur during the proton-proton chain? a. protons are converted to Helium b. neutrinos are released c. mass is converted into energy 11. The Solar neutrino problem: a. arises because too few neutrinos are counted here on Earth b. arises because too many neutrinos are counted here on Earth c. arises because the Sun does not produce neutrinos d. arises because the outer layers of the Sun block the passage of neutrinos 12. A probable solution to the Solar neutrino problem is: a. that neutrinos oscillate between different types of neutrinos b. that we do not understand the interior of the Sun c. that the neutrino detectors do not work 2
Stellar Evolution 13. What fundamental parameter primarily dictates the fate of a star? a. its radius b. its location in the Galaxy c. its mass d. its position in the sky e. its color 14. A main sequence star is one in which: a. Hydrogen is being fused into Helium b. Helium is being fused into Carbon c. Carbon is being fused into Nitrogen d. Nitrogen is being fused into Oxygen 15. Which stars live longer? a. high mass stars b. low mass stars c. middle-mass stars d. blue stars e. a and d 16. After a star finishes converting Hydrogen into Helium, it becomes a a. giant star b. main sequence star c. a protostar 17. In about 5 billion years, the Sun will: a. become a giant star b. engulf some of the inner planets in the Solar System c. become cooler and larger d. become redder and larger e. all of the above 18. Planetary nebulae a. result from giant stars losing their atmospheres b. surround white dwarf stars c. are gas clouds where stars and their planets form 19. A critical stage in a star's evolution occurs when a. a flare occurs b. an HR diagram is constructed c. iron is left in the core 20. A possible way for a star to alter its fate before its ultimate death is through a. mass loss by stellar winds b. fusion of iron in its core c. ejection from the Galaxy d. a Slim Fast diet 21. A star less massive than 1.4 times the mass of the Sun, at the end of its life, will a. become a white dwarf b. become a neutron star c. become a black hole 22. A star less massive than 1.4 times the mass of the Sun, at the end of its life, will a. collapse to a singularity b. be supported by neutron degeneracy pressure c. be supported by electron degeneracy pressure 23. White dwarfs are a. very luminous b. very faint c. very hot d. a and b e. b and c 3
24. Which is smaller in diameter? a. a White Dwarf b. the Sun c. a Red Giant d. a Neutron star e. a Supergiant 25. A star less massive than 3 times the mass of the Sun, but greater than 1.4 times the mass of the Sun, at the end of its life, will a. become a white dwarf b. become a neutron star c. become a black hole 26. Pulsars a. can be detected in the radio b. are neutron stars c. are supported by neutron degeneracy pressure 27. A star more massive than 3 times the mass of the Sun, at the end of its life, will a. become a white dwarf b. become a neutron star c. become a black hole 28. An object traveling at the speed of light a. is traveling at the fastest speed possible b. must have no mass c. must be very massive 29. Black holes can be detected by a combination of: a. direct images/photographs of the black holes themselves b. x-ray emission from accretion disks surrounding a black hole c. the Doppler wobble of a companion star d. a and b e. b and c 30. Black holes are a. the result of a high-mass star's death b. a result of severely curved spacetime c. regions where not even light can escape Discovering Galaxies 31. In a spiral galaxy like ours, if one does not account for it, interstellar dust results in a. the appearance that the Sun is near the edge of the Galaxy b. the appearance that the Sun is near the center of the Galaxy c. the appearance that the Galaxy is spherical 32. The fact that the Sun does not lie at the center of the distribution of globular clusters means that a. the Milky Way is not warped b. the clusters are in elliptical orbits around the Sun c. the Sun is not at the center of the Milky Way d. we don't understand star clusters e. the Sun is the center of the Universe 4
33. Shapley determined the distance to globular clusters by means of pulsational variables. He was able to do so because: a. one can derive the period of a pulsational variable from its light curve b. pulsational variables obey a period-luminosity relation c. the distance of pulsational variables can be found from parallax 34. Shapley derived the size of the Milky Way from the distance to globular clusters. He concluded that the Milky Way is a. a large galaxy, some 300,000 LY across b. a small galaxy, some 25,000 LY across c. the one and only galaxy d. a and c e. b and c 35. The "true" distance to the Andromeda "nebula" was derived by Hubble using a. Cepheid variables b. the proper motion and transverse velocity of Andromeda c. parallax of stars within Andromeda 36. Hubble's determination of the distance to Andromeda showed that a. the Milky Way was the only galaxy b. the Milky Way was one of many galaxies c. there was interstellar dust d. Cepheid distances were unreliable 37. Shapley argued that if the Andromeda nebula were a galaxy like our own, with its observed angular size, then it would be so far away that the "new star" seen in the Andromeda "nebula" in 1888 would have to be a supernova. He argued this could not be the case, and therefore Andromeda was located within the confines of the Milky Way. His argument a. was incorrect because the star was a less luminous nova b. was valid because supernovae weren't known at that time c. was valid because Andromeda is not really outside of the Milky Way d. a and c e. b and c Galaxies, Active Galaxies 38. The Milky way a. is the only galaxy in the Universe b. is one of hundreds of billions of galaxies c. is one of a few galaxies known d. is at the center of the Universe e. b and d 39. Galaxies come in several types. Among them are a. spiral galaxies b. barred spiral galaxies c. elliptical galaxies d. irregular galaxies e. all of the above 5
40. The most common type of galaxies may likely be: a. normal spirals, that are easy to detect b. giant ellipticals, that are easy to detect c. low surface brightness galaxies, of dwarf galaxies, that are difficult to detect d. barred spirals e. all are equally common 41. Which of the following statements are true? a. elliptical galaxies can evolve to become spiral galaxies b. elliptical galaxies can form numerous stars due to their high gas content c. spiral galaxies can form stars in their disks, but not in their halos d. all of the above are true are true 42. Rotation curves of galaxies are determined by a. measuring the velocities of stars in at various locations in galaxies b. taking long exposure photographs of galaxies, and charting the path of the stars c. counting the number of stars at various distances from the centers of galaxies 43. Evidence for dark matter comes from: a. rotation curves of galaxies b. the velocities of stars and gas in galaxies c. the inference that more mass is present than can be seen d. all of the above 44. Giant elliptical galaxies are likely that way because: a. they have not yet shed most of their mass b. they are the result of mergers and acquisitions c. they were formed that way d. they were misclassified e. they evolved from the collapse of a larger spiral galaxy 45. What is the source of energy within most active galaxies? a. quasars b. supermassive black holes c. Stephen Hawking d. supermassive neutrinos e. synchrotron radiation Cosmology 46. The Hubble Law tells us that: a. we are at the center of the universe, since all galaxies are moving away from us b. we are falling into a black hole at the center of the Milky Way c. the Universe is contracting 47. The Hubble constant is useful because it can be used to estimate: a. how old the universe is b. how far a galaxy is, if you know its velocity c. the expansion rate of the Universe 6
48. To derive the Hubble constant: a. one must know the distances to galaxies b. one must account for all of the matter in the Universe c. one must know the velocities of galaxies 49. The observed 3K background radiation: a. was discovered by accident b. was predicted before it was observed c. is a remarkable match to what is predicted by theory 50. The most surprising result to date, as far as the expansion of the Universe is concerned, is: a. the Universe is sinking into a supermassive black hole b. the expansion of the Universe is accelerating c. we can't stop it d. galaxies are receding from us e. we know where it is going 7