Download 1st EXAM VERSION C - Department of Physics and Astronomy

ASTRONOMY 113
EXAM #1: Covering Chapters 18-20
Time: 3:00-4:15pm
VERSION “C”
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1. The highest temperatures found in the Sun is located in the
A.
chromosphere
B.
corona
C.
photosphere
D.
*core
E.
cytosphere
2. We see an emission nebula predominantly in
A. blue light, originally emitted by stars within the nebula but scattered by
dust.
B. light emitted over a wide range of wavelengths by dust grains that have
been heated by radiation from embedded stars.
C. light emitted by molecules in the dense clouds of gas surrounding the stars
in the nebula.
D. *red line, from recombination of electrons with nuclei in ionized
hydrogen.
3. In the magnetic model for the bipolar outflow from a protostar
A. magnetic field lines emanate from the poles of the protostar and carry
material outward from the stellar interior.
B. *magnetic field lines through the circumstellar accretion disk become
twisted and concentrated by the rotation of this disk.
C. magnetic field lines associated with the galaxy as a whole are concentrated
and shaped by their interaction with the magnetosphere of the protostar.
D. the jets are formed along magnetic field lines, which go from the north
magnetic pole of one protostar to the south magnetic pole of a second
protostar which forms a close binary pair with the first.
4. Sunspots are
A.
B.
C.
D. *
E.
areas obscured by higher layers of clouds
ashes of nuclear burning brought to the surface by convection
holes in the photosphere that allow us to see deeper regions
regions which are cooler and darker than surrounding material
causing global warming
5. Energy generation in the Sun results from
A.
fission of uranium
B.
fission of hydrogen
C.
gravitational contraction
D.
the Sun isn't generating energy; it's just cooling
E. *
fusion of hydrogen
6. What are the most energetic eruptive events to occur on the Sun?
A. thermonuclear explosions
B. erupting prominences
C. *coronal mass ejections
D. solar flares
7. The phrase “hydrostatic equilibrium” in the Sun refers to
A. the balance of gas pressure outward and magnetic forces inward.
B. the creation of one helium nucleus for the “destruction” of every four
hydrogen nuclei.
C. the balance of gas pressure inward and heat outward.
D. *the balance of gravity inward and gas pressure outward.
8. Most of the Sun's energy is produced in
A.
supergranules
B.
the convection zone
C.
the photosphere
D.
the chromosphere
E. *
the core
9. An astronomer observing certain regions of the Sun through a spectrograph
notices that the spectral lines emitted from these regions are split into two or more
components. What can the astronomer conclude about these regions from this
observation?
A. They contain fast-moving gas, moving away from the observer
B. They are very hot
C. They contain strong gravitational fields.
D. *They contain strong magnetic fields.
10. If the Hipparchos satellite measures the parallax motion of a star against the
background stars and concludes that the star has a parallax of 0.004 arcseconds,
how far is that star from Earth?
A. *250 pc or 800 ly
B. 0.004 pc or 0.013 ly
C. 25 pc or 81 ly
D. 400 pc or 1300 ly
11. Energy is transported from the center of the Sun to the surface
A. by radiation in the central thermonuclear core and convection through the
rest of the interior.
B. mostly by convection but with radiation in the outer layers.
C. by convection in the central thermonuclear core and radiation through the
rest of the interior.
D. *mostly by radiation but with convection in the outer layers.
12. Consider the spectral classification of stars using only the letters A B F G K M O.
When these are arranged in order from coolest to hottest they would be:
A.
O-B-A-F-G-K-M
B. *
M-K-G-F-A-B-O
C.
A-B-O-F-G-K-M
D.
M-K-G-F-O-B-A
E.
B-A-G-K-O-M-F
13. Spicules on the solar surface are
A. streams of solar coronal material, usually seen only during a total solar eclipse.
B. curtain-like structures hanging over sunspot regions.
C. intense eruptions from sunspot groups and active regions, associated with
solar flares.
D. *jets of gas surging out of the photosphere of the Sun into the
chromosphere, usually at supergranule boundaries.
14. Which of the following is most likely to get to Earth from the core of the Sun,
before any of the others?
A.
protons
B.
electrons
C.
photons
D. *
neutrinos
15. During the sunspot cycle the position of new sunspots on the Sun
A. *
changes from mid-latitudes to the equator
B.
changes from mid-latitudes to the poles
C.
changes from the equator to the mid-latitudes
D.
changes from the equator to the poles
E.
does not change in any predictable manner
16. Sunspot cycles are, on the average, what length?
A.
22 years
B. *
11 years
C.
5.5 years
D.
1 year
E.
3 years
17. What is a characteristic of all Main Sequence stars?
A.
helium is fused into carbon in the core and energy is released
B. *
hydrogen is fused into helium in the core and energy is released
C.
interstellar molecules are fused
D.
they are the hottest of all stars
E.
they are the largest of all stars
18. The correct order of the layers of the Sun from innermost to outermost is:
A.
core, chromosphere, photosphere
B.
core, convective layer, radiative layer
C.
radiative layer, convective layer, core
D.
convective layer, core, radiative layer
E. *
core, radiative layer, convective layer
19. One of the conclusions from the mass-luminosity relationship is that
A. *
bright main sequence stars are more massive than faint main
sequence stars
B.
giants are more massive than main sequence stars
C.
giants are more massive than white dwarfs
D.
main sequence stars are more massive than white dwarfs
E.
all of the above are true
20. The star Alderamin has an apparent magnitude of 2.4 and an absolute magnitude
of 1.4. The star Merak has an apparent magnitude of 2.4 and absolute magnitude
of 0.5. Assuming that neither star has been dimmed by interstellar clouds, we can
say for sure that
A. Merak and Alderamin are the same distance from us.
B. *Merak is farther away from us than Alderamin.
C. Merak is an intrinsically fainter star than Alderamin.
D. Merak is closer to us than Alderamin.
21. Using the Hertzsprung-Russell diagram above, determine which type of star has
the following characteristics: surface temperature of 40,000 K and luminosity
100,000 times that of the Sun.
A. white dwarf
B. main sequence red dwarf
C. red giant
D. *blue main sequence star
22. What is the physical reason that astronomers can find the luminosity class (I, II,
III, IV, or V) of a star using the star's spectrum?
A. The relative amounts of hydrogen, helium, and other elements are
different for stars of different luminosity classes.
B. *The absorption lines in the spectrum are affected by the density and
pressure of the star's atmosphere.
C. The absorption lines in the spectrum are affected by the star's surface
temperature.
D. The wavelength of maximum emission (given by Wien's law) is affected
by the size of the star.
23. Coronal mass ejections are
A.
large bits of the sun that blow out into interplanetary space
B. *
charged particles from the sun accelerated/guided by magnetic
field lines
C.
richer in heavier elements than other mass ejections
D.
nothing to be feared by spacecraft and humans in space
E.
never going to achieve escape velocity
24. An eclipsing binary system is
A. two stars whose spectral lines move back and forth, indicating relative
motion.
B. a star that is periodically eclipsed by the Moon.
C. *two stars whose combined light output when measured from Earth
appears to vary periodically as the two stars move in front of one another.
D. two stars that are clearly seen as separate but associated in the sky.
25. Absorption lines in the spectra of some binary stars are seen to change
periodically from single to double lines and back again. Why is this?
A. Oscillations on the surfaces of the stars leads to Doppler-shifted lines.
B. Periodically, the magnetic field of one star produces Zeeman splitting of
spectral lines in atoms of the second star.
C. The effect of the gravitational field of one star on the atoms of the second
star produces spectral line shifts periodically.
D. *Motion toward and away from Earth during their orbital motion results in
Doppler shift of light from these stars at times and no shift when the stars
are moving perpendicular to the line of sight.
26. The effect of interstellar dust on starlight is
A. *to dim and redden distant stars by preferentially scattering their blue
light.
B. to scatter the red light from stars preferentially, making them appear more
blue than expected.
C. almost nonexistent, because light does not interact with dust.
D. to make stars appear less bright than expected by absorbing light about
equally at all wavelengths.
27. The star Ross 128 in the constellation Virgo has an apparent magnitude of 11
while the star Luyten 789-6 has an apparent magnitude of 12. The star that is
brighter is how many times brighter than the dimmer star?
A.
Ross 128 is approximately 1 times brighter than Luyten 789-6
B.
Luyten 789-6 is approximately 2.5 times brighter than Ross 128
C. *
Ross 128 is approximately 2.5 times brighter than Luyten 789-6
D.
Ross 128 is approximately 10 times brighter than Luyten 789-6
E.
Luyten 789-6 is approximately 10 times brighter than Ross 128
28. Two objects are moving closer together. Each will see the other's light
A.
red-shifted
B.
better than if moving apart
C.
richer in heavier elements
D. *
blue-shifted
E.
shifted towards microwave region of the spectrum
29. All of the statements comparing the Sun to the Giant stars are true except which
of the following? (look at the HR diagram above)
A. The Giant stars are more luminous than the Sun.
B. The Giant stars are larger than the Sun.
C. *The Giant stars are hotter that the Sun
D. The Giant stars have smaller absolute magnitude than the Sun
30. Which part of the Hertzsprung-Russell diagram is occupied by protostars?
A. to the left of the main sequence
B. a band running from upper right to lower left
C. *to the right of the main sequence
D. a band running from upper left to lower right
31. Which of the following statements is characteristic of a T Tauri star?
A. great age-near the end of its life as a star
B. *ejection of mass into space
C. high mass-;greater than about 3 solar masses
D. nuclear reactions in the core
32. Two objects have the same size and different temperatures. The hotter object is
A. *
bluer and brighter than the cooler object
B.
bluer and fainter than the cooler object
C.
redder and brighter than the cooler object
D.
redder and fainter than the cooler object
E.
None of the above can be true.
33. The following table gives the name, absolute magnitude (M), apparent magnitude
(m), and spectral type for five stars. Answer the following five questions using
this table and the appropriate letter corresponding to the star that is best described
by the line given. Note that stars/letters may be used more than once.
Star
Name
M
m
SpT
A
Aldeberan
-0.5 +0.9 K5III
B
Antares
-3.8 +1.0 M2I
C
Deneb
-7.2 +1.3 A2I
D
Fomalhaut
+2.0 +1.2 A3V
E
Spica
-3.5 +1.0 B1III
34. Which star appears brightest in the sky to us on Earth?
A.
*
B.
C.
D.
E.
35. Which star would be the brightest in the sky if all stars were at the same distance?
A.
B.
C.
*
D.
E.
36. Which star has the coolest surface temperature?
A.
B.
*
C.
D.
E.
37. Which star is the most distant from Earth?
A.
B.
C.
*
D.
E.
Cannot be determined with the information given
38. Which star is a Main Sequence star?
A.
B.
C.
D.
*
E.
More than one is a Main Sequence star
39. What happens to the core temperature of a collapsing nebula that eventually
produces a star?
A.
The core temperature decreases.
B.
*The core temperature increases.
C.
The core temperature remains the same.
D.
Either A or B can occur depending on the initial mass of the gas cloud.
E.
Either A, B or C can occur depending on the initial mass of the gas cloud.
40. What determines whether a particular region of an interstellar cloud can collapse
and form a star?
A. only the temperature, because higher temperatures act to prevent collapse
B. the relative concentration of dust to hydrogen gas in the cloud, because the
dust is the major trigger that initiates collapse
C. *the amount of gravity pulling inward compared to gas pressure pushing
outward
D. the amount of mass in the cloud alone, because this determines the
strength of gravity, which will act unopposed on the cloud
41. Which one of the following statements is correct for an isolated star (i.e., a star
that is not in a binary star system
A. *It is not possible to measure the star's mass accurately.
B. There are several ways to measure its mass accurately.
C. Its mass can be measured accurately only if its luminosity and temperature
can be measured.
D. Its mass can be measured accurately only if its distance can be found.
42. A reflection nebula is made visible by
A. thermal energy emitted as a continuous spectrum by very hot gas, much
like that emitted by a hot body on Earth.
B. *blue light, preferentially scattered by tiny dust grains.
C. emission lines from hydrogen, which itself has been ionized by UV light
from embedded stars.
D. light from embedded stars reflected over a wide range of wavelengths
toward Earth, by crystals of water, methane, and ammonia ices.
43. If we plot the stars in a YOUNG star cluster on a Hertzsprung-Russell diagram,
we would expect to see
A. the more massive stars above the main sequence and the less massive stars
on the main sequence.
B. all of the stars above the main sequence because none have evolved to the
main-sequence stage.
C. *all stars on the main sequence.
D. the more massive stars on the main sequence and the less massive stars
above the main sequence.
44. How are distances to a star determined using the technique known as
spectroscopic parallax?
A.
By using a spectroscope during the measurements for parallax
B.
By determining the apparent magnitude of the star
C.
By determining the spectral class of the star and using an H-R
diagram
D. *
Both B and C above are required to determine a distance to star
E.
none of the above can provide an estimate of distance
45. When the Sun was forming, before it reached the main sequence, its energy was
generated primarily by
A.
chemical reactions
B.
helium fusion
C.
hydrogen fusion
D.
nuclear fission
E. *
gravitational contraction
46. The solar cycle is determined by the change in the
A.
solar constant
B.
sunspot location and number
C. *
solar magnetic field polarity
D.
solar electric field changes
E. *
solar magnetic field polarity