PH109 Exploring the Universe, Spring 2001, Test #3
Please indicate the best answer to the following questions on the answer sheet provided. Each question is worth 2 points.
1. When young stars form jets that then slam into the rest of the cloud forming bright nebular which are called
a. T Tauri stars, b. Herbig-Haro objects
c. O associations, d. WIMPs, e. Giant molecular clouds
2. If we counted all the stars that are currently on the main sequence, which spectral type would be most abundant?
a. A, b. B, c. K, d. M
3. The primary reason for the 22 year sunspot cycle is
a. Orbit of Jupiter, b. Alignment of the planets every 22 years.
c. magnetic field reversal d. enhanced synchrotron radiation
4. Pulsars give off mostly which kind of radiation
a. positronic b. spinar c. synchrotron d. circumstellar
5. Sunspots usually occur
a. as single regions, b. in pairs,
c. in groups of three or more, d. as continuous regions around the sun's equator
6. What mechanism is responsible for the twisting of the Sun's magnetic filed lines?
a. differential rotation, b. convection, c. proton-proton cycle, d. tidal forces
7. The fact that convection is occurring in the outer layers of the Sun is demonstrated by
a. solar eruptions, b. sunspots, c. granules, d. solar wind
8. Which element is the Sun currently fusing
a. Hydrogen, b. Helium, c. Carbon, d. Oxygen
9. What will be the last element that the Sun will be able to "burn"
a. Hydrogen, b. Helium, c. Carbon, d. Oxygen
10. In a science fiction movie a local star will soon become super nova after it finishes burning Iron. What is wrong with this statement?
a. stars that burn Iron do not go super nova
b. Iron can only be produced in a super nova
c. no star can burn Iron
d. stars do not go super nova, pulsars do
11. The neutral hydrogen atom consists of
a. one proton and one neutron.
b. one proton.
c. one proton, one neutron, and one electron.
d. one proton and one electron.
e. an isotope and an ion.
12. The two most abundant elements in the sun are
a. nitrogen and oxygen, b. hydrogen and helium,
c. sulfur and iron, d. carbon and hydrogen,
e. carbon and nitrogen.
13. A plot of the continuous spectra of five different stars are shown in the figure below. Based on these spectra, which of the stars is the hottest?
a. Star A, b. Star B, c. Star C, d. Star D, e. Star E
14. In the diagram below, which of the transitions would absorb a photon with the greatest energy.
a. 1, b. 2, c. 3, d. 4, e. 5
15. You are standing near a railroad track and a train is moving toward you at 60 mph and blowing its horn. What will you notice as the train moves past you?
a. As the train approaches, the horn will sound lower in pitch than when it is moving away.
b. As the train approaches, the horn will sound higher in pitch than when it is moving away.
c. There will be no change in the pitch of the horn as it moves by.
d. The horn will get louder as the train moves away from you.
e. The horn will get quieter as the train moves toward you.
16. The diagram below illustrates a light source, a gas cloud, and three different lines of sight. Along which line of sight would an observer see an continuous spectrum?
a. 1, b. 2, c. 3, d. 2 and 3, e. none of them
17. Most of the light we see coming from the sun originates in the
a. chromospheres, b. photosphere, c. corona
d. sunspots, e. magnetic field
18. Sunspots are dark because
a. regions of the photosphere are obscured by material in the chromospheres.
b. shock waves move through the photosphere.
c. the sun rotates differentially.
d. the strong magnetic field inhibits the currents of hot gas rising from below.
e. they radiate their energy into space faster than the rest of the photosphere.
19. The centers of granules
a. are hot material rising to the photosphere from below.
b. are cool material falling from the photosphere to the regions below.
c. are fainter and hotter than their surroundings.
d. are brighter and cooler than their surroundings.
e. show strong Zeeman effects.
20. A recent sunspot maximum occurred in 1990, what is the year of the sunspot maximum that immediately follows the 1990 maximum if the solar cycle continues?
a. 1995 or 1996, b. 2001, c. 2006, d. 2012
e. the last cycle started a Maunder minimum and the next maximum can not be predicted.
21. In the H-R diagram, 90 percent of all stars are
a. in the giant region, b. in the supergiant region,
c. among the B stars, d. among the G stars,
e. on the main sequence
22. In a binary system, the more massive star
a. is at the center of mass.
b. is farthest from the center of mass.
c. is nearest the center of mass.
d. follows the largest orbit.
e. shows a larger Doppler shift in its spectral lines.
23. Which of the following stars is most dense?
a. a supergiant star
b. a main sequence star
c. a giant star
d. a white dwarf
e. the sun
24. A spectroscopic binary shows periodic variations in its
a. radial velocity.
b. proper motion.
c. brightness.
d. mass.
e. spectral type.
25. The total mass of a binary system can be calculated from
a. the ratio of the angular separation from the center of mass of each of the stars.
b. the distance to the binary and its radial velocity.
c. the semi major axis and period of the orbit.
d. the radial velocities of the two stars.
e. the time required for the small star to eclipse the larger star.
26. What causes the outward pressure that balances the inward pull of gravity in a star?
a. The outward flow of energy.
b. The opacity of the gas.
c. The temperature of the gas
d. The density of the gas
e. Both the temperature of the gas, and the density of the gas.
27. ______occurs when most of the material collapsing to form a protostar has fallen into a disk around the star and a strong wind from the warm protostar ejects material from its poles.
a. An emission nebula
b. Hydrostatic equilibrium
c. The proton-proton chain
d. The thermonuclear fusion of hydrogen
e. A bipolar flow
28. The main sequence has a limit at the lower end because
a. low mass stars form from the interstellar medium very rarely.
b. low mass objects are composed primarily of solids, not gases.
c. pressure does not depend on temperature in degenerate matter.
d. the lower limit represents when the radius of the star would be zero.
e. there is a minimum temperature for hydrogen fusion.
29. Stars are born in
a. reflection nebulae, b. dense molecular clouds, c. HII regions.
d. the intercloud medium, e. the local bubble
30. Giant and supergiant stars are rare because
a. they do not form as often as main sequence stars.
b. the giant and supergiant stage is unstable.
c. the giant and supergiant stage is very short.
d. helium is very rare.
e. helium flash destroys many of the stars before they can become giants and supergiants.
31. Star cluster are important to our study of stars because
a. all stars formed in star clusters.
b. the sun was once a member of a globular cluster.
c. they give us a method to test the our theories and models of stellar evolution.
d. they are the only objects that contain Cepheid variables.
e. all of these
32. What is the approximate age of the star cluster in the diagram below?
a.2 million years, b.2 billion years, c.10 billion years, d. 100 billion years
e. The age of the cluster can not be estimated from an HR diagram of the cluster.
33. A planetary nebula is
a. the expelled outer envelope of a medium mass star.
b. produced by a supernova explosion.
c. produced by a nova explosion.
d. a nebula within which planets are forming.
e. a cloud of hot gas surrounding a planet.
34. Synchrotron radiation is produced by
a. objects with temperature below 10,000 K.
b. high-velocity electrons moving through a magnetic field.
c. cold hydrogen atoms in space.
d. the collapsing cores of massive stars.
e. helium flash.
35. The Algol paradox is explained by considering
a. the degenerate nature of the hydrogen on the surface of the white dwarf.
b. synchrotron radiation
c. the rate of expansion of the shock wave inside the supernova.
d. the rotation rate of a neutron star.
e. mass transfer between the two stars in a binary system.
36. Stars with masses between 0.4 and 4 solar masses
a. undergo thermonuclear fusion of hydrogen and helium, but never get hot enough to ignite carbon.
b. undergo thermonuclear fusion of hydrogen, but never get hot enough to ignite helium.
c. produce type-I supernovae after they exhaust their nuclear fuels.
d. produce type-II supernovae after they exhaust their nuclear fuels.
e. undergo carbon detonation.
37. The event horizon
a. is believed to be a singularity.
b. is a crystalline layer.
c. has a radius equal to the Schwarzschild radius.
d. marks the inner boundary of a planetary nebula.
e. is located at the point where synchrotron radiation is created around a pulsar.
38. The density of a ______is greater than the density of a ______.
a. white dwarf neutron star
b. neutron star black hole
c. pulsar neutron star
d. pulsar white dwarf
e. white dwarf black hole
39. The material that accretes onto a neutron star or black hole is expected to emit x-rays because
a. the material will produce synchrotron radiation.
b. hydrogen nuclei begin to fuse and emit high energy photons.
c. the material will become hot enough that it will radiate most strongly a x-ray wavelengths.
d. as the material slows down it converts thermal energy to gravitational potential energy.
e. none of these
40. Why don't all supernova remnants contain pulsars?
a. All supernova remnants do contain pulsars.
b. Some supernova explosions form white dwarfs instead of the neutron stars necessary for pulsars.
c. Pulsars slow down and quite producing the pulses before the supernova remnant dissipates.
d. The pulsar may be tipped so that the beams do not sweep past Earth.
e. Both some supernova explosions form white dwarfs instead of the neutron stars necessary for pulsars, and pulsars slow down and quite producing the pulses before the supernova remnant dissipates.
41. The spectral classification of our Sun is
a) O, b) B, c) G, d) M
42. The Sunspot cycle is related to
a) the age of the Sun
b) the magnetic field reversals in the sun’s core
c) the rate at which Hydrogen in converted into Helium in the Sun’s core
d) the revolution period of the planet Jupiter
43. A ______is a planet sized star supported by degenerate electrons
a) super novae, b) white dwarf, c) neutron star, d) pulsar
44. How fast could pulsars pulse
a) one per second, b) one per year, c) up to 1000 per second, d) up to one million per second
45. If the Sun were replaced by a black hole having a mass of one solar mass, what would happen to the Earth's orbit?
a) the Earth would spiral inward
b) the Earth would jump to a smaller orbit
c) the size of the Earth's orbit would increase rapidly
d) the Earth's orbit would remain the same
46. Which of the following spectral types is the hottest?
a) G2, b) A5, c) K9, d) O2
47. What physical property of a star does the spectral type measure?
a) luminosity, b) temperature, c) radius, d) mass
48. The final core element for a massive star is
a) carbon, b) oxygen, c) silicon, d) iron
49. A surface explosion on a white dwarf, caused by falling matter from the atmosphere of its binary companion, creates what kind of object?
a) Nova, b) Type-I supernova, c) Type-II supernova, d) Contact binary
50. Nearly all the elements found in our environment were formed inside stars. The major exceptions are:
a) Iron and nickel, b) Oxygen and carbon, c) Silver and technetium, d) Hydrogen and helium