NAME ______________________________________________

Astronomy 122
Final Examination
December 7, 2006

Formulas
W = 3x10⁷/T(K) Angstroms
F = constant T⁴ [power per unit area]
L = 12.6 constant R²T⁴ [power]
F = L/(12.6 D²) [power per unit area]
E = mc²

Multiple Choice Questions -- 60 questions @ 2 points per question ----> 120 points

Select the best answer for each question.

1. Of the following parts of the electromagnetic spectrum, which pass freely through the atmosphere of the Earth?

a. x-rays and optical
b. radio and ultraviolet
*c. radio and optical
d. ultraviolet and optical
e. infrared and gamma-rays

2. Main Sequence stars are of luminosity class _____ .

a. I
b. II
c. III
d. IV
*e. V

3. Two stars have the same surface temperature. The larger star `has a radius 2 times greater than the smaller one. The larger star radiates how much more energy than does the smaller one?

a. 2 times as much
*b. 4 times as much
c. 8 times as much
d. 16 times as much
e. 64 times as much

4. An atom is held together (bound) by ____ .

a. the gravitational force
b. the nuclear force
*c. the electrical force
d. a combination of the electrical and greavitational forces
e. a mysterious force unknown to modern science

5. The luminosity of the Sun _____ the Solar Activity Cycle.

*a. changes by less than 1 % over
b. doubles in size over
c. is 10 times larger around the maximum of
d. drops to 0 around the minimum of

6. The Russell-Vogt Theorem states that the properties of a star are determined primarily by the star's _____ .

a. luminosity and radius
b. mass and luminosity
c. mass, chemical composition, and radius
d. radius and chemical composition
*e. mass and chemical composition

7. When the Universe started to expand 13.7 billion years ago, it was made primarily of _______ .

a. nitrogen and oxygen
b. silicon (sand)
*c. hydrogen and helium
d. carbon and water
e. carbon, nitrogen, and oxygen

8. The masses of stars on the Main Sequence _____ .

*a. increase from the lower right to the upper left
b. decrease from the lower right to the upper left
c. are all the same
d. have random values along the Main Sequence
e. depend strongly on the age of the star

9. Accurate measurements of stellar parallax are important because they allow the direct determination of _____ .

a. the masses of stars
b. the surface temperatures of stars
c. the orbital periods of binary stars
*d. the distances to stars
e. the chemical composition of stars

10. The nucleus of an atom is composed of _____ .

a. neutrons
b. protons
c. electrons
d. *a and b only
e. a, b, and c

11. Binary star systems are particularly important for _____ .

*a. the determination of the masses of stars
b. the determination of the distances to stars
c. the determination of the speeds with which stars move
d. the determination of the luminosities of stars
e. the determination of the surface temperatures of stars

12. The Sun is of spectral type _____ .

a. O6
b. A2
c. F8
*d. G2
e. S2

13. A brown dwarf is _______.

a. a low mass main sequence star
b. a dirty low mass main sequence star
*c. a failed star; an object that never got hot enough to ignite nuclear fusion in its core
d. a planet like the Earth
e. a smallish unusually cold sunspot

14. The bright red emission nebulas known as H II regions form _______.

a. around stars like the Sun
b. in regions where you typically find planets
c. around binary star systems
*d. around massive, hot stars
e. around every protostar we have seen

15. The _______ while it is on the Main Sequence.

*a. Sun's luminosity slowly increases
b. Sun's mass slowly increases
c. Sun converts helium to carbon and oxygen in a thin shell outside of its core
d. Sun’s surface temperature doubles
e. Sun’s luminosity varies periodically by 50 % every 22 years

16. The hottest layer of the Sun’s atmosphere is the _______.

a. magnetosphere
b. photosphere
c. chromosphere
d. convective layer
*e. corona

17. An annihilation is when _______.

*a. a matter particle and its anti-matter twin collide and are converted into energy (radiation)
b. a massive nucleus fissions into two smaller nuclei
c. sunspots collide and coalesce on the Sun during Solar maximum
d. four hydrogen nuclei are fused to form one helium nucleus
e. an electron neutrino is transformed into a tau neutrino

18. The corona of the Sun has a temperature of _____.

a. 5,800 K
b. 4,500 K
c. 100,000 K
*d. 1,000,000-3,000,000 K
e. 10,000,000-15,000,000 K

19. A Reflection Nebula requires the presence of which of the following?

a. carbon and water
b. a brown dwarf and hydrogen gas
*c. dust and a massive star (an O or B star)
d. dust and a planetary nebula
e. hydrogen and helium gas

20. The Chandrasekhar limit is ______.

*a. the maximum mass a white dwarf may have
b. the minimum mass a main sequence star may have
c. the maximum mass a main sequence star may have
d. the fastest rate at which the Sun can rotate
e. the dividing line between high mass and low mass stars

21. After the carbon burning phase of evolution, most of the energy from nuclear reactions is lost through _____.

a. the emission of light (photons)
b. strong stellar winds
c. CMEs
*d. neutrinos
e. high speed protons

22. Sirius is a bright main sequence star. Sirius has mass of 2.1 times as massive as the Sun. Sirius will eventually wind up as a _____.

a. supernova
b. black hole
c. neutron star
*d. white dwarf
e. brown dwarf

23. The _____ is used to determine the age of the cluster.

a. number of stars in a stellar cluster
*b. main sequence turn-off of a stellar cluster
c. number of white dwarfs in a stellar cluster
d. shape of a stellar cluster
e. position in the Milky Way galaxy of a stellar cluster

24. Black dwarfs are _____.

a. the lowest mass main sequence stars
b. the end result of the evolution of ultra-massive stars
c. objects not quite massive enough to become stars
d. the material ejected from highly evolved brown dwarfs
*e. the cooled off remnants of white dwarfs

25. Hydrogen burning in the core of a star like the Sun lasts for _____.

a. 200 million years
b. 10 thousand years
*c. 10 billion years
d. 10 trillion years
e. 10 million years

26. The speed for radio waves versus X-rays through vacuum is _____.

a. greater for radio waves due to their longer wavelength
b. greater for X-rays due to their shorter wavelength
c. greater for X-rays due to their higher energy
d. greater for X-rays due to their greater penetrating power
*e. the same for radio waves and X-rays

27. The feature which all Main Sequence stars share is _____ .

a. they are all in hydrostatic equilibrium
b. they are all in thermal equilibrium
c. they are all composed primarily of hydrogen and helium
d. they all generate energy by the conversion of hydrogen into helium in their cores
*e. All of the above are features of Main Seqeunce stars.

28. Type II Supernovas in spiral galaxies like our own Milky Way are found _____ .

a. in clusters of black holes
b. primarily in the outer edges of the galaxy.
*c. in or near spiral arms
d. only in the center of the galaxy
e. at any random location in the disk of the galaxy

29. If the Sun was replaced by a black hole of the same mass, _____ .

a. the Earth would quickly spiral into the Sun because of an increase in the strength of gravity
b. the Earth would rapidly spiral away from the Sun because a drop in the strength of gravity
*c. there would be only small effects on the motion of the Earth
d. the Earth would immmediately vaporize because of an increase in gravity
e. the Earth would be transported to a different point and time in the Universe.

30. A crucial role supernovas play in the scheme of cosmic evolution is that _____ .

a. supernovas enrich the Universe in neutrinos
*b. heavy elements are produced in supernovas
c. supernovas produce most of the light seen in other galaxies
d. supernovas are harbingers of important events for mankind
e. supernovas are the source of the hydrogen needs for water.

31. The collapse of the core of the massive star in a Type II supernova stops _____ .

a. nuclear fusion is ignited
b. when the electrons become degenerate
*c. when the material becomes as dense as material found in the nucleus of an atom
d. the core becomes a black hole
e. the core becomes a black dwarf

32. The energy (photons) produced in the center of the Sun reaches the Earth in roughly _______ .

a. 2.3 seconds
b. 8.3 minutes
c. a month
d. a year
*e. 170,000 years or so

33. According to Kirchhoff's laws, a planetary nebula should exhibit _______ .

a. an absorption line spectrum
b. only a continuous spectrum
c. only a blackbody spectrum
*d. an emission line spectrum

34. Atoms in a hot, thin gas (such as a neon advertising sign), emit light _______ .

a. at only one specific wavelength
b. only at visible wavelengths
c. at all wavelengths, i.e., in a continuous spectrum
*d. at very specific wavelengths depending on its chemical composition

35. The Maunder Minimum occurred in the 1600s. The Maunder Minimum was _______.

a. an extended period of abnormally long nights
b. the first mention of sunspots in ancient texts
c. the first recorded example of the disappearance of Solar neutrinos
*d. an extended period of low Solar activity (few sunspots)
e. All of the above are true.

36. The spectral class of a star tells us the _______.

*a. temperature of the surface of the star
b. temperature of the center of the star
c. average temperature inside of the star
d. luminosity class of the star
e. mass of the star

37. The SNO experiment has recently shown that _______ .

*a. neutrinos are chameleon-like in nature; they can change from one type to another
b. the Maunder Minimum led to a global ice age in the 1600s
c. interstellar space travel is a viable way to study stars
d. the Sun is actually composed of carbon and oxygen
e. protons are composed of quarks

38. Einstein's famous equation E = mc² says that _______ .

a. electrical forces are the same as mass
b. energy is determined by how fast a particle moves
*c. energy is equivalent to mass
d. the speed of light depends on the energy of the photon
e. energy is the same thing as motion

39. The Heisenberg Uncertainty Principle says that _______ .

a. we cannot predict how long a star like the Sun will live, even roughly
b. all electromagnetic radiation travels at the same speed
c. matter and energy are different forms of the same physical quantity
*d. the exact location and precise motion of a particle cannot be determined simultaneously
e. we will never be able to find a blackbody in our Universe

40. Most stars have absorption line spectra. This suggests that _______ .

a. stars are made of hot, transparent gas
b. stars are made of cool, transparent gas
c. stars are cool dense objects surrounded by a layer of hotter, transparent gas
*d. stars are hot, dense objects surrounded by a layer of cooler, transparent gas
e. stars are hot, dense objects surrounded by a layer of even hotter, transparent gas

41. Electromagnetic radiation is a carrier of information. The specific information that it carries is that _____ .

a. somewhere in the Universe, a star is moving toward us
b. somewhere in the Universe, a star is moving away from us
*c. somewhere in the Universe, an electrical charge is accelerating ( moving)
d. somewhere in the Universe, nuclear reactions are taking place
e. somewhere in the Universe, a star is dying

42. The news of events which occur inside of the Event Horizon of a Black Hole in our Universe _______.

a. take around 170,000 years to reach an observer on the Earth
b. can only reach the Earth if Einstein's result that E = mc² is incorrect
*c. can never reach an observer on the Earth
d. reach the Earth in around 8.3 minutes
e. can only reach the Earth is neutrinos are chameleon-like in nature

43. A clock runs ______ when it is near the Event Horizon of a Black Hole than when it is far from the Black Hole.

*a. more slowly
b. at the same rate, time is the one constant in our Universe upon which we can rely
c. more quickly
d. the answer depends upon whether it is a digital clock or an analog clock.

44. The highest speed to which a slowly moving object can be accelerated _______.

a. is the escape speed for the Universe
*b. is almost the speed of light
c. is infinite; there is no upper limit to the speed to which an object can be accelerated
d. to the speed beyond which the object becomes a black hole
e. is the escape speed for the object

45. Nucleosynthesis refers to _______.

a. the process of tunneling
b. the process of binary star formation
*c. the process of element building
d. the technique used to measure the ages of stellar clusters
e. the manner in which we believe star formation was first triggered

46. Star formation in the Milky Way galaxy _______.

a. occurred in a single burst around 10-12 billion years ago, just after the Universe was born
b. has been ongoing, and will continue until the end of the Universe
*c. has been ongoing but is expected to cease in a few billion years
d. has been increasing over time until, currently, more than a billion stars form every year
e. primarily occurs in the regions remote from spiral arms

47. Strong evidence that star formation occurs around spiral arms is _______.

a. black holes tend to cluster near spiral arms
b. neutron stars cluster around spiral arms
c. K and M stars are concentrated along spiral arms
*d. H II regions cluster along spiral arms
e. the Sun is in a spiral arm

48. Main Sequence stars like the Sun next evolve into _______.

a. planetary nebulas
b. white dwarfs
c. neutron stars
*d. red giants
e. asymptotic giant branch stars

49. After the initial outburst of SN 1987A waned, the main source for its luminosity was energy released from _______.

*a. the radioactive decay of elements like Nickel and Cobalt
b. continuing nuclear fusion reactions in the ejected material
c. the ultraviolet radiation from the hot stellar remnant
d. neutrino heating from the core
e. the kinetic energy (the energy of motion) of the expanding material

50. Type II Supernova outbursts are triggered by _______>

a. electron captures
b. photo-disintegration of iron
c. the violent onset of the nuclear fusion reactions involving iron
*d. a & b
e. a, b, & c

51. The protostar phase ends when _______.

a. a planetary nebula forms
b. the protostar reaches the white dwarf stage
c. the protostar becomes dense and starts to trap radiation
*d. hydrogen burning commences in its core
e. the protostar supernovas

52. Hydrogen burning in the core of a star 10 times the mass of the Sun lasts for roughly _______ .

*a. 10 million years
b. 1 billion years
c. 100 billion years
d. 100 thousand years
e. 20 trillion years

53. For stars undergoing helium burning in their cores, the dominant form for the escaping energy is _______.

a. neutrinos
*b. photons
c. the ejection of the envelope of the star
d. induced rapid oscillations in the size of the star
e. sound waves

54. Star formation can be triggered by _______.

a. spiral arms
b. supernovas
c. stellar winds
d. nearby hot, massive stars
*e. all of the above

55. We believe that star formation is an ongoing process in other galaxies because _______.

a. we have watched countless stars be born, evolve, and then die in supernova outbursts
*b. we see extensive H II regions in other galaxies
c. we see many stars less massive than 0.1 solar masses in other galaxies
d. we see many white dwarfs in other galaxies
e. all of the above

56. The story of a star's evolution is the story of its constant battle to _______.

*a. overcome the effects of gravity
b. maintain the imbalance between matter and anti-matter in its core
c. maintain its high mass
d. maintain its Activity cycle
e. overcome the electrical barrier between electrons in its core

57. The mass of a black hole is contained _______.

a. in a thin shell just inside of the event horizon
*b. at its center in the singularity
c. in a thin shell just outside of the event horizon
d. throughout the volume inside the event horizon
e. the exotic particles known as tachyons

58. The existence of black holes was first suggested by _______.

a. Einstein in the middle of the last century
*b. Michell and Laplace in the late 1700s
c. Hawking in the late 1960s
d. the observation of SN1987A
e. Newton in the 1600s

59. The escape speed of a black hole whose mass is 10 times that of the Sun is _______.

a. 1 % of the speed of light
b. 10 % of the speed of light
*c. the speed of light
d. 10 times the speed of light
e. 100 times the speed of light

60. The Event Horizon of a black hole is _______.

a. the radius of the progenitor star of the black hole when it was on the Main Sequence
b. the surface which marks the extent of the mass contained in the black hole
c. the theoretical size of the singularity of the black hole
d. the size of the progenitor star of the black hole when it arrived on the Zero Age Main Sequence
*e. the surface from where the escape speed is the speed of light

Short Answer Questions -- 8 questions @ 10 points per question ----> 80 points

1. Describe how the strengths of the hydrogen lines vary along the spectral sequence (O ---> M). For which spectral class are hydrogen lines the strongest? Explain why the strength of the hydrogen lines in the spectra of stars varies as one moves along the spectral Sequence (O ---> M).

2. Why are neutrinos the most useful probes for the study the energy genetation mechanisms of the Sun? Why are neutrinos more useful than measures of the current luminosity of the Sun? What has been learned from the Solar neutrino studies in terms of both the properties of the Sun itself and the properties of neutrinos?

3. Describe how astronomers determine the surface temperatures of stars from their continuous spectra and their absorption line spectra.

4. Why can the Sun be considered a variable star? Cite the effects which show that the Sun is a variable star. Cite evidence and explain why the evidence suggests that there are links between variability of the Sun and the climate on the Earth.

5. What is the observational evidence that suggests that our understanding of Type II Supernovas is reasonably good? Explain how the evidence cited improved (tested) our understanding of Type II Supernovas.

6. What is the Cosmic Censorship Theorem? Is this a theorem or a conjecture? What are implictions of the Cosmic Censorship Theorem? What is meant by Black Holes Have No Hair? What are some implications of the Black Holes Have No Hair theorem?

7. Sketch a Hertzsprung-Russell (HR) diagram. Be sure to label the axes and indicate the locations of the Main Sequece, Super-Giants, normal Giants, and white dwarfs. Sketch the evolutionary track of a star 25 times the mass of the Sun.

8. Why is nuclear fusion difficult? (What is the major impediment to fusion?) What is meant by tunneling? Explain why tunneling is important for nuclear fusion in the Sun.