Astronomy 122&, Fall 2009
Homework F: Due Friday, November 6.
Multiple choice. On your scantron fill out your NAME,
and NETWORK ID both in writing and in the bubbles. In
addition, fill out "FORM F."
1. Open clusters are found in the
a) Milky Way (the disk of our Galaxy)
b) Galaxy's halo
c) Galaxy's nucleus
d) Solar System
e) Alpha Centauri system
2. Globular clusters are
a) found in the Galaxy's halo
b) much more massive than open clusters
c) are the oldest objects known
d) are much rarer than open clusters
e) all of the above
3. Old star clusters are missing
a) their lower main sequences
b) their upper main sequences
c) their giant branches
d) their white dwarfs
e) nothing
4. How old are the oldest star clusters in billions of years?
a) 0.5 b) 1 c) 3 d) 12 e) 30
5. The classic case of a white dwarf is the companion to
a) the Sun
b) Jupiter
c) Deneb
d) Sirius
e) Alpha Centauri
6. Diffuse nebulae shine by
a) photoionization by ultraviolet light and subsequent
recombination
b) nuclear fusion
c) reflection from dust grains only
d) shock waves only
e) magnetic heating
7. Interstellar dust is made mostly of
a) iron and titanium
b) hydrogen and helium
c) ammonia and methane
d) silicon and carbon
e) water and carbon dioxide
8. Most of the gas within a molecular cloud is in the form of
a) helium
b) carbon monoxide
c) carbon dioxide
d) water
e) molecular hydrogen
9. Which is not a molecule found in interstellar space?
a) carbon monoxide
b) alcohol
c) ammonia
d) water
e) protein
10. The cores of stars just beginning life on the main sequence are
made mostly of
a) hydrogen
b) helium
c) carbon
d) silicon
e) iron
11. What helps slow a rotating cloud that helps it become a
star?
a) cosmic rays and the galactic magnetic field
b) tides raised by the Galaxy
c) collisions with stars
d) ultraviolet light
e) all of the above
12. What chills the dark clouds so that stars can form?
a) convection
b) conduction
c) radiation
d) dust that blocks starlight
e) all of the above
13. Stars are currently being born in
a) old star clusters
b) giant molecular clouds
c) the Kuiper Belt
d) diffuse nebulae
e) reflection nebulae (those that shine by reflection of light
from dust grains)
14. T Tauri stars and Herbig-Haro objects are associated with
a) dark dust clouds
b) planetary nebulae
c) globular clusters
d) old open clusters
e) all of the above
15. Developing stars form disks because of the conservation of
a) mass
b) energy
c) heat
d) angular momentum
e) velocity
16. The age of a globular cluster is found from
a) its radial velocity
b) the highest-mass stars found in the cluster
c) the lowest-mass stars found in the cluster
d) the amount of dust in the cluster
e) the number of stars it contains
17. What observations provide evidence for the existence of planets
orbiting other stars?
a) direct observation of the planets
b) transits across the stellar disk
c) observations of dusty disks around new stars
d) slight variations in the stars' radial velocities
e) all of the above
18. When the Sun was born, it was
a) brighter than now
b) somewhat dimmer than now
c) exactly the same as now
d) a white dwarf
e) much more massive than it is now
19. Which kind of main sequence star will live the shortest period
of time and explode?
a) F b) O c) A d) G e) M
20. The nuclear-fusing core of the Sun is
a) slowly expanding and heating
b) slowly contracting and heating
c) staying the same
d) slowly expanding and cooling
e) slowly contracting and cooling
21. The Sun will create a
a) planetary nebula
b) white dwarf
c) giant star
d) all of the above
e) none of the above
22. What evidence is there for intelligent life in the Universe
(other than ourselves)?
a) UFOs
b) aliens on television
c) radio radiation from other stars
d) laser radiation from other stars
e) none
23. Where on the HR diagram do we find brown dwarfs?
a) at the top of the main sequence
b) below the lower end of the hydrogen-fusing main
sequence
c) on the giant branch
d) among the hot white dwarfs
e) among the cool white dwarfs
24. Above what mass (in solar masses) are main sequence stars
expected to explode, that is, to become supernovae?
a) 0.08 b) 0.8 c) 10 d) 1000 e) 1000
25. A star climbing the giant branch for the first time has a core
made of
a) helium
b) hydrogen
c) carbon
d) oxygen
e) iron
26. What keeps the Sun from rapid collapse, that is, what supports
it?
a) gravity
b) thermonuclear fusion in the core
c) rapid rotation
d) magnetic fields
e) nothing
27. The fusion of what element stops the first ascent of the giant
branch?
a) helium
b) hydrogen
c) carbon
d) oxygen
e) iron
28. A star climbing the giant branch for the second time has a core
made of
a) helium
b) hydrogen
c) carbon and oxygen
d) silicon
e) iron
29. What does helium fuse into?
a) silicon
b) hydrogen
c) iron
d) carbon
e) nothing
30. What kinds of stars fuse helium?
a) white dwarfs
b) stars like the Sun
c) stars just being born
d) giant stars
e) none
31. White dwarfs are made mostly of
a) hydrogen
b) helium and hydrogen
c) carbon and oxygen
d) iron and nickel
e) titanium and vanadium
32. Stars like Mira, those climbing the giant branch for the second
time, will turn into, or produce
a) supernovae
b) planetary nebulae
c) brown dwarfs
d) main sequence stars
e) diffuse nebulae
33. What stage of stellar life follows the planetary nebula?
a) red giant
b) nothing
c) supernova
d) white dwarf
e) brown dwarf
34. White dwarfs are formed by stars that start off in the mass
range
a) 0.8 to 10 solar
b) 10 to 100 solar
c) 0.08 to 0.8 solar
d) under 0.08 solar
e) over 100 solar
35. The maximum allowed mass for a white dwarf is (in solar
masses)
a) 0.08 b) 0.8 c) 1.0 d) 1.4 e) 2.8
36. White dwarfs do not collapse under their own gravity because
of
a) hydrogen fusion
b) helium fusion
c) carbon fusion
d) the pressure of degenerate protons
e) the pressure of degenerate electrons
37. What do planetary nebulae have at their centers?
a) new white dwarfs
b) neutron stars
c) giant stars
d) supergiant stars
e) main sequence stars
38. Where does a lot of the interstellar dust come from?
a) solar type stars
b) neutron stars
c) Mira variables
d) brown dwarfs
e) white dwarfs
39. A high-mass star that generates an iron core will become a
a) white dwarf supernova
b) core-collapse (Type II) supernova
c) white dwarf
d) planetary nebula
e) carbon star
40. The upper mass limit for neutron stars (in solar masses) is
about
a) 0.08 b) 0.8 c) 1.4 d) 3 e) 10
41. The "event horizon" of a black hole (the apparent "surface") is
the surface at which
a) the gravitational force equals the strong force
b) the speed of light becomes zero
c) the speed of light becomes infinite
d) the escape velocity equals the speed of light
e) gravity disappears
42. From an isolated black hole (one with no companion or nearby
gas) we would observe or detect
a) gravity and light (electromagnetic radiation)
b) gravity but no light
c) light but no gravity
d) neither light nor gravity
e) X-rays
43. The brightest kind of "star" is the
a) neutron star
b) core-collapse supernova
c) Type Ia white dwarf supernova
d) planetary nebula
e) AGB (second ascent giant) star
44. Cosmic rays are
a) high energy gamma rays produced by hot white dwarfs
b) rays of starlight shining through holes in the distribution
of interstellar dust
c) streams of stars that have all formed at the same time
d) high-speed atomic nuclei launched by supernovae
e) the lines of force of the Galaxy's magnetic field
45. Pulsars are
a) rotating white dwarfs
b) pulsating white dwarfs
c) rotating neutron stars
d) pulsating neutron stars
e) Cepheid variables
46. An ordinary white dwarf can produce a supernova if
a) it has a companion
b) it gets hit by a pulsar
c) its iron core collapses
d) it is made of hydrogen instead of carbon
e) is rotating quickly enough
47. What evidence is there that black holes actually exist?
a) there is one in our Solar System
b) there is one orbiting Alpha Centauri
c) we see otherwise normal stars that are also bright X-ray
sources
d) we see otherwise normal stars that are also bright infrared
sources
e) the existence of pulses of radiation from the Crab
Nebula
48. The iron content of the Galaxy
a) is currently decreasing
b) is currently constant
c) is currently increasing
d) once increased but is now decreased
e) once decreased but is now staying constant
49. The Crab Nebula is
a) a diffuse nebula
b) a planetary nebula
c) the remnant of a nova
d) a supernova remnant
e) none of the above
50. What is the contribution of supernovae to star and planet
formation?
a) shock waves
b) cosmic rays
c) iron
d) all of the above
e) none of the above