Download Sample Stellar Evolution TEST QUESTIONS

E:\2012-2013\SSU\PHY 207 spring 2013\stellar evolution\ Sample Stellar Evolution Test 1 of 13 pages
Sample Stellar Evolution test for 2nd test Monday March 18, 2013 in MH 541 from 6 to 7:15 pm;
After all the tests are collected, the answers will be reviewed.
Multiple Choice Questions
1.. Parallax would be easier to measure if
a. Earth's orbit were larger.
b. the stars were farther away.
c. Earth moved faster along its orbit.
d. all of these
e. none of these
2. If a star has a parallax of 0.02 seconds of arc, then its distance is
a. 20 pc
b. 50 pc
c. 2 pc
d. 5 pc
e. 500 pc
3. Absolute visual magnitude is
a. the apparent magnitude of a star observed from Earth.
b. the luminosity of a star observed from a distance of 1000 pc.
c. the apparent magnitude of a star observed from a distance of 10 pc.
d. the luminosity of a star observed from Earth.
e. a and d.
4. . The ________________of a star is a measure of the total energy radiated by the star in
one second.
a.
b.
c.
d.
e.
absolute visual magnitude
apparent visual magnitude
luminosity class
spectral type
luminosity
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5. The region of the Sun just below the photosphere
a.
is undergoing thermonuclear fusion using the proton-proton chain.
b.
is undergoing thermonuclear fusion using the CNO cycle.
c.
is transporting energy to the photosphere by convection.
d.
is not in hydrostatic equilibrium.
e.
a and c above
6. 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.
c and d
7. The nuclear reactions in a star's core remain under control so long as
a.
luminosity depends on mass.
b.
pressure depends on temperature.
c.
density depends on mass.
d.
weight depends on temperature.
e.
temperature depends on mass.
8. Convection is important in stars because it
a.
increases the temperature of the star.
b.
mixes the gases of the star.
c.
transports energy outward in the star.
d.
carries the neutrinos to the surface of the star where they can escape.
e.
b and c
9. Which of the following nuclear fuels does a one solar mass (1 Mo) star use over
the course of its entire evolution?
a.
b.
c.
d.
e.
hydrogen
hydrogen and helium
hydrogen, helium and carbon
hydrogen, helium, carbon, and neon
hydrogen, helium, carbon, neon, and oxygen.
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10. Stars are born in
a.
reflection nebulae.
b.
dense molecular clouds.
c.
MI regions.
d.
the intercloud medium.
e.
the local bubble.
11. Protostars are difficult to observe because
a.
the protostar stage is very short.
b.
they are surrounded by cocoons of gas and dust.
c.
they radiate mainly in the infrared.
d.
all of the above
e.
they are all so far away that the light hasn't reached us yet.
12. 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.
13.- The lowest mass object that can initiate thermonuclear fusion of hydrogen has a mass of
about
a.
1 Mo.
b.
60 Mo.
c.
0.5 Mo.
d.
0.08 Mo
e.
0.001 Mo
14. There is a mass-luminosity relation because
a.
b.
c.
d.
e.
hydrogen fusion produces helium.
stars expand when they become giants.
stars support their weight by making energy.
the helium flash occurs in degenerate matter.
all stars on the main sequence have about the same radius.
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15. In an H-R Diagram, stars with the smallest radius are found in the ______________ of the
diagram.
a.
b.
c.
d.
e.
center
upper left corner
upper right corner
lower left corner
lower right corner
16. In the H-R diagram, 90 percent of all stars are
a.
b.
c.
d.
e.
in the giant region.
in the supergiant region.
among the B stars.
among the G stars.
on the main sequence.
17. The hydrogen lines in spectral type A stars
a. are most narrow for supergiants.
b. are most narrow for main sequence stars.
c. can not be used to estimate the luminosity of the star.
d. are very weak and difficult to see.
e. are useful in determining the apparent magnitude of die star.
18. Sheat is an M2 II star. Based on this information which of the following are true?
I. Sheat has a surface temperature less than the sun.
II. Sheat has a diameter that is greater than that of the sun.
III. Sheat is more luminous than the sun.
IV. Sheat is located near the upper left hand corner in the HR diagram.
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19.  Circini is an 0 8.5 V star. Based on this information which of the following are true?
I. Circini has a surface temperature less than the sun.
II. Circini has a diameter that is greater than that of the sun.
III.  Circini is more luminous than the sun.
IV.  Circini is located near the upper left hand corner in the HR diagram.
20. Which star in the diagram
above is most like the sun?
a.
b.
c.
d.
e.
Alnilam
Antares
Arcturus
HR 5337
Sirius B
21. Which star in the diagram above has the greatest surface temperature?
a. Alnilam
b. Antares
c. Arcturus
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d. HR 5337
e. Sirius B
22. Which of the stars in the diagram above has the largest absolute visual magnitude?
a.
b.
c.
d.
e.
Alnilam
Antares
Arcturus
HR 5337
Sirius B
23. Which of the following best obey the mass-luminosity relation?
a. main sequence stars
b. giant stars
c. supergiant stars
d. white dwarfs
e. all of the above
24. 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
25. Stars on the main sequence with the greatest mass
a. are spectral type G stars.
b. are spectral type 0 stars.
c. are located at the bottom of the main sequence in the H-R diagram.
d. have masses very similar to the sun.
e. both b and c
Use the following chart to answer the next four questions.
Star
m,
My
d (pc)
Parallax
(sec of arc)
Spectral
Type
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65 Tau
4.2
HR 4621 2.6
 Pic
3.3
58 Ori
12.5
HR 2491 -1.5
1.2
-0.3
1.8
-6.0
1.5
0.025
20
0.005
2.5
A7 IV
B2 IV
A7 V
M2 I
Al V
26. Which star in the table above would appear the faintest in the night sky?
a.
b.
c.
d.
e.
65 Tau
HR 4621
 Pic
58 Ori
HR 2491
27. Which star in the table above has the greatest luminosity?
a.
b.
c.
d.
e.
65 Tau
HR 4621
 Pic
58 Ori
H-R 2491
28. Which star in the table above is the closest to Earth?
a.
b.
c.
d.
e.
65 Tau
HR 4621
 Pic
58 Ori
HR 2491
29. Which star in the table above has the greatest surface temperature?
a.
b.
c.
d.
e.
65 Tau
HR 4.621
 Pic
58 Ori
HR 2491
30. As a star exhausts hydrogen in its core, it
a.
b.
c.
c.
d.
becomes hotter and more luminous.
becomes cooler and more luminous.
becomes hotter and less luminous.
becomes cooler and less luminous.
becomes larger in radius and hotter.
31. Stars with masses between 0.4 Mo.and 4 Mo
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.
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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.
32. Massive stars cannot generate energy through iron fusion because
a. iron fusion requires very high density.
b. stars contain very little iron.
c. no star can get hot enough for iron fusion,
d. iron is the most tightly bound of all nuclei.
e. massive stars supernova before they create an iron core.
33. The lowest-mass stars cannot become giants because
a. they do not contain helium.
b. they rotate too slowly.
c. they cannot heat their centers hot enough.
d. they contain strong magnetic fields.
e. they never use up their hydrogen.
34. 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.
35. Due to the dust in the interstellar medium(ISM), a star will appear to an observer on Earth to
be
a. brighter and cooler than it really is.
b. brighter and hotter than it really is.
c. fainter and cooler than it really is.
d. fainter and hotter than it realty is.
e. unchanged in brightness or apparent color.
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36. The extinction of starlight due to the interstellar medium (ISM)
I.
II.
III.
IV.
is the greatest in the ultraviolet.
is the greatest in the infrared.
is caused by ionized hydrogen.
is caused by dust particles.
a.
b.
I & II
II & III
c. I& IV
d. II & IV
e. only IV
37. Absorption lines due to the interstellar medium (ISM) indicate that some components of
the interstellar medium (ISM) are cold and of a very low density because
the lines are blue shifted.
the lines are red shifted.
the lines are extremely broad.
d. the lines are extremely narrow.
e. the lines are much darker than the stellar lines.
a.
b.
c.
38. Absorption lines due to interstellar gas
a. are wider than the lines from stars because the gas is hotter than most stars.
b. are more narrow than the lines from stars because the gas has a lower pressure than
stars.
c. indicate that the interstellar medium contains dust.
d. indicate that the interstellar medium is expanding away from the sun.
e. e, none of the above
39. Giant stars are
I.
II.
III.
IV.
more luminous than the sun.
larger in diameter than the sun.
Cooler than B stars.
located above the main sequence stars in the H-R diagram.
40. Compared with the spectral lines in the solar spectrum, lines in a supergiant spectrum are
a.
b.
c.
d.
e.
more narrow.
broader.
weaker.
stronger.
b&c
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41. We know that giant stars are larger in diameter than the Sun because
a.
b.
c.
d.
e.
they are more luminous but have about the same temperature.
they are less luminous but have about the same temperature.
they are hotter but have about the same luminosity.
they are cooler but have about the same luminosity.
they have a larger absolute magnitude than the sun.
42. A planetary nebula is
a. the expelled outer envelope of a medium mass star.
b. produced by a supernova explosion produced by a nova explosion.
c. a nebula within which planets are forming.
d. cloud of hot gas surrounding a planet.
43. A planetary nebula
a. produces an absorption spectrum.
b. produces an emission spectrum.
c. is contracting to form planets.
d. is contracting to form a star.
e. is the result of carbon detonation in a 1 Mc, star.
44. A white dwarf is composed of
a.
b.
c.
d.
e.
hydrogen nuclei and degenerate electrons.
helium nuclei and normal electrons.
carbon and oxygen nuclei and degenerate electrons.
degenerate iron nuclei.
a helium burning core and a hydrogen burning shell.
45. The maximum mass of a white dwarf is ___solar masses. (1 Mo.= 1 solar mass)
a. Less than 1 Mo.,
b. slightly less than 2 Mo. or < 2 Mo.
c. more than 2 Mo. or > 2 Mo.
d. slightly more than 1 Mo. or > Mo.
e. much larger than 4 Mo. or > 4 Mo.
46. A nova is almost always associated with
a. a very massive star.
b. a very young star.
c. a star undergoing helium flash.
d. a white dwarf in a close binary system.
e. a solar like star that has exhausted its hydrogen and helium.
47. The diagram on the right shows a light curve from a supernova.
r
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How many days after the maximum light (at 0 magnitude) did it take for the supernova to
decrease in brightness by a factor of 5 magnitudes?
a.
b.
c.
c.
d.
less than 50
50
150
250
more than 250
48. A Type I supernova is believed to occur when
a. the core of a massive star collapses.
b. carbon detonation occurs.
c.a white dwarf exceeds the Chandrasekhar limit.
d. the cores of massive stars collapse.
e.neutrinos in a massive star become degenerate and form a shock wave that explodes the star.
Fill in the Blank Questions
1. The condition of ___________ means that the force due to gravity pushing down on a layer is
exactly equal to the pressure pushing outward on that layer.
2.. A gas in which the pressure no longer depends on the temperature of the gas is said to be
3. A(n) ___________ is the expulsion of the outer layers of a moderate mass star that has a
degenerate carbon and oxygen core.
4. Energy transport ___________________ is important when photons cannot readily
travel through a gas.
True-False Questions
1
A star whose parallax is 0.01 seconds arc is at a distance of 1000 pc.
2
The method of spectroscopic parallax can be applied to stars beyond about 100 pc.
3. The absolute magnitude of a star is the apparent magnitude it would have if it
were 10 pc from Earth.
4. The location of a star in the H-R diagram indicates its temperature and intrinsic
brightness.
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5. Absorption lines in the spectra of supergiant stars are broader than the same
spectral lines in main sequence stars of the same spectral type.
6. Ninety percent of all stars fuse helium to form carbon and lie on the main
sequence.
7. Nuclear fusion in stars is controlled by the dependence of density on mass.
8. The Sun has a core in which energy travels outward primarily by radiation.
9. Energy flows by radiation or convection inside stars but almost never by
conduction.
10. Hydrostatic equilibrium refers to the balance between weight and pressure.
11. The Orion region contains young main sequence stars and an emission nebula.
12. The thermal motions of the atoms in a gas cloud can make it collapse to form a
protostar.
13. The pressure of a gas generally depends on its temperature and its density.
14. Stars swell into giants when hydrogen is exhausted in their centers.
15. Planetary nebulae are sites of planet formation.
16. Stars less massive than 0.4 solar mass never become giant stars.
17. No known white dwarf has a mass greater than the Chandrasekhar limit.
18. Because more massive stars have more gravitational energy, they can fuse heavier
nuclear fuels.
19. The Sun will eventually become a supernova.
20. Type II supernovae are believed to occur when the cores of a massive stars
collapse.
21. Type II supernova produces a planetary nebula.
22. A nova destroys the star and leaves behind a white dwarf.
23. If a star is twice as hot as the Sun and only half the sun's diameter, it will be less
luminous than the sun.
24. The most common kinds of stars are low-luminosity stars.
25. Supergiants are about as common as the sun.
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26. White dwarfs have such a low luminosity that even the nearest white dwarfs are not
visible to the naked eye.
27. The most massive main-sequence stars are the M stars.
28. The densest stars in the H-R diagram are the white dwarfs.
29. The Sun has a core in which energy travels outward primarily by radiation.
30. Energy flows by radiation or convection inside stars but almost never by conduction.
31. The dust in the interstellar medium can make distant. stars look redder than they
really are.
Essay Questions
1.
Why would parallaxes be easier to observe if Earth were farther from the sun?
2.
How does an H-R diagram make it clear that giant stars are larger than
main-sequence stars of the same temperature?
3.
How does the luminosity depend on temperature for stars of the same size?
4.
How do the spectra of giants, and supergiants differ from main-sequence stars?
5.
How can we find the distance to a star that is too distant to have a measurable
parallax?
6.
Which are the most common stars, massive stars or low-mass stars?
7.
Why do nuclear reactions in a star occur only near its center?
8.
Explain what keeps the nuclear reaction in a star under control.
9.
Why are interstellar absorption lines so narrow?
10.
Why are massive stars more luminous than low mass stars?
11.
Why is there a lower end to the main sequence?
12.
Why do nuclear reactions in a star occur only near its center?
13. If white dwarfs have exhausted their fuel, why are they hot?
14. What is the difference between a supernova and a nova?
THE END