Question 1

Molecular clouds, which have temperatures of around 10 K, are best observed at ________ wavelengths.

Accepted Answer

A)   X-ray
B)   ultraviolet
C)   optical
D)   infrared
E)   radioF) A) and E)
G) B) and C)

Question 2

Magnetic fields inside a molecular cloud act to

Accepted Answer

A)   inhibit gravitational collapse.
B)   fragment the cloud into numerous cores.
C)   modulate the temperature of the molecules.
D)   increase the formation of dust grains.
E)   increase the formation of protostars.F) A) and B)
G) None of the above

Question 3

Dust in the ISM appears dark in ________ wavelengths and bright in ________ wavelengths.

Accepted Answer

A)   visible; ultraviolet
B)   infrared; radio
C)   infrared; visible
D)   radio; ultraviolet
E)   visible; infraredF) All of the above
G) B) and C)

Question 4

Suppose we observe two molecular clouds containing dust.The dust in Cloud 1 peaks in emission at 50 mm, while the dust in Cloud 2 peaks in emission at 78 mm.How much warmer is the dust in Cloud 1 compared to Cloud 2?

Accepted Answer

The peak of the emission is related to the dust temperature via Wien's law,so that T₁ = 2,900 µm and T₂= 2,900 µm .The ratio of the two clouds' temperatures is then

Question 5

What is the interstellar medium made of? Give rough percentages of each.

Accepted Answer

The ISM is 99 percent gas and 1 percent ...

Question 6

Bipolar outflows create bright bow shocks because

Accepted Answer

A)   the gas "piles up" when it encounters ultraviolet light.
B)   the material collides with particles in the interstellar medium.
C)   the star's magnetic fields trap the outflow material there.
D)   the gas cools enough to allow H -  ions to build up.
E)   the outflows encounter newly forming planets.F) A) and B)
G) A) and D)

Question 7

A protostar's evolutionary "track" in the H-R diagram traces

Accepted Answer

A)   only how the protostar's radius changes with time.
B)   how the protostar's luminosity, temperature, and radius change with time.
C)   only how the protostar's luminosity changes with time.
D)   only how the protostar's spectral type changes with time.
E)   the protostar's location in the molecular cloud.F) B) and C)
G) A) and D)

Question 8

Dust that glows with a peak emission wavelength of 40  μ\muμ m has a temperature of

Accepted Answer

A)   10 K.
B)   72 K.
C)   100 K.
D)   120 K.
E)   1000 K. F) A) and C)
G) A) and B) B

Question 9

Compare the volume of the Sun with the volume of interstellar space it dominates.Is the occupied percentage large or small? Consider the volume around the Sun to be a sphere whose radius is equal to the distance to the nearest star, which is equal to 5 light-years.(Note: the radius of the Sun is 7 *105 km, and 1 light-year = 9.5 * 1012 km.)

Accepted Answer

The volume occupied by the Sun is given ...

Question 10

Stars forming in molecular clouds tend to form first in

Accepted Answer

A)   the low-density periphery.
B)   the high-density core.
C)   random locations.
D)   any location where the temperature is highest.
E)   the location with the heaviest elements.F) A) and B)
G) A) and C) B

Question 11

Star formation is an inefficient process, with only a few percent of the initial cloud fragment ending up as stars.This means the initial mass of a molecular cloud fragment that formed a 2 MSUN star was probably close to

Accepted Answer

A)   1 MSUN.
B)   50 MSUN.
C)   100 MSUN.
D)   5,000 MSUN.
E)   1,000,000 MSUN.F) D) and E)
G) C) and D)

Question 12

How are Herbig-Haro objects related to T Tauri stars?

Accepted Answer

Herbig-Haro objects are ionized gas form...

Question 13

Electronic transitions from the H2 molecule are easily seen at

Accepted Answer

A)   X-ray wavelengths.
B)   visible wavelengths.
C)   radio wavelengths.
D)   infrared wavelengths.
E)   ultraviolet wavelengths.F) A) and E)
G) A) and D)

Question 14

A young protostar is ________ than the Sun even though its surface temperature is ________.

Accepted Answer

A)   less luminous; hotter.
B)   larger; hotter.
C)   smaller; the same.
D)   more luminous; cooler.
E)   smaller; hotter.F) B) and D)
G) A) and B)

Question 15

What happens as a protostar contracts?

Accepted Answer

A)   Its density rises.
B)   Its temperature rises.
C)   Its radius decreases.
D)   Its pressure rises.
E)   All of these are true.F) A) and E)
G) C) and D)

Question 16

Dust that is heated to 30 K will emit a blackbody spectrum that peaks near

Accepted Answer

A)   1 µm.
B)   30 µm.
C)   50 µm.
D)   100 µm.
E)   500 µm.F) B) and C)
G) A) and D)

Question 17

If you wanted to observe heavy elements in the interstellar medium, where would be the best place to look?

Accepted Answer

A)   dust grains
B)   cold gas
C)   hot gas
D)   warm gas
E)   the interiors of forming protostars.F) D) and E)
G) A) and B)

Question 18

The average density of the interstellar medium is

Accepted Answer

A)   1 atom/cm3.
B)   1,000 atoms/cm3.
C)   104 atoms/cm3.
D)   106 atoms/cm3.
E)   1012 atoms/cm3.F) B) and C)
G) A) and D)

Question 19

Molecular cloud cores are places where you might find

Accepted Answer

A)   protostars.
B)   Herbig-Haro objects.
C)   molecular hydrogen (H2) .
D)   carbon monoxide (CO) .
E)   all of theseF) B) and C)
G) None of the above

Question 20

How long does it typically take for a protostar to form a 1 MSUN star?

Accepted Answer

A)   3 *107 years
B)   3 * 105 years
C)   3,000 years
D)   300 years
E)   30 yearsF) A) and C)
G) C) and E)

Exam 15: The Interstellar Medium and Star Formation

Molecular clouds, which have temperatures of around 10 K, are best observed at ________ wavelengths.

Correct Answer
verified

Magnetic fields inside a molecular cloud act to

Correct Answer
verified

Dust in the ISM appears dark in wavelengths and bright in wavelengths.

Correct Answer
verified

Suppose we observe two molecular clouds containing dust.The dust in Cloud 1 peaks in emission at 50 mm, while the dust in Cloud 2 peaks in emission at 78 mm.How much warmer is the dust in Cloud 1 compared to Cloud 2?

What is the interstellar medium made of? Give rough percentages of each.

Correct Answer
verified
The ISM is 99 percent gas and 1 percent ...
View Answer

Bipolar outflows create bright bow shocks because

Correct Answer
verified

A protostar's evolutionary "track" in the H-R diagram traces

Correct Answer
verified

Dust that glows with a peak emission wavelength of 40 $\mu$ m has a temperature of

Correct Answer
verified
B

Correct Answer
verified
The volume occupied by the Sun is given ...
View Answer

Stars forming in molecular clouds tend to form first in

Correct Answer
verified
B

Star formation is an inefficient process, with only a few percent of the initial cloud fragment ending up as stars.This means the initial mass of a molecular cloud fragment that formed a 2 M_SUN star was probably close to

Correct Answer
verified

How are Herbig-Haro objects related to T Tauri stars?

Correct Answer
verified
Herbig-Haro objects are ionized gas form...
View Answer

Electronic transitions from the H₂ molecule are easily seen at

Correct Answer
verified

A young protostar is than the Sun even though its surface temperature is .

Correct Answer
verified

What happens as a protostar contracts?

Correct Answer
verified

Dust that is heated to 30 K will emit a blackbody spectrum that peaks near

Correct Answer
verified

If you wanted to observe heavy elements in the interstellar medium, where would be the best place to look?

Correct Answer
verified

The average density of the interstellar medium is

Correct Answer
verified

Molecular cloud cores are places where you might find

Correct Answer
verified

How long does it typically take for a protostar to form a 1 M_SUN star?

Correct Answer
verified

Exam 15: The Interstellar Medium and Star Formation

Molecular clouds, which have temperatures of around 10 K, are best observed at ________ wavelengths.

Correct AnswerverifiedShow Answer

Magnetic fields inside a molecular cloud act to

Correct AnswerverifiedShow Answer

Dust in the ISM appears dark in ________ wavelengths and bright in ________ wavelengths.

Correct AnswerverifiedShow Answer

Suppose we observe two molecular clouds containing dust.The dust in Cloud 1 peaks in emission at 50 mm, while the dust in Cloud 2 peaks in emission at 78 mm.How much warmer is the dust in Cloud 1 compared to Cloud 2?

What is the interstellar medium made of? Give rough percentages of each.

Correct AnswerverifiedThe ISM is 99 percent gas and 1 percent ...View AnswerShow Answer

Bipolar outflows create bright bow shocks because

Correct AnswerverifiedShow Answer

A protostar's evolutionary "track" in the H-R diagram traces

Correct AnswerverifiedShow Answer

Dust that glows with a peak emission wavelength of 40 μ\muμ m has a temperature of

Correct AnswerverifiedB

Correct AnswerverifiedThe volume occupied by the Sun is given ...View AnswerShow Answer

Stars forming in molecular clouds tend to form first in

Correct AnswerverifiedB

Star formation is an inefficient process, with only a few percent of the initial cloud fragment ending up as stars.This means the initial mass of a molecular cloud fragment that formed a 2 MSUN star was probably close to

Correct AnswerverifiedShow Answer

How are Herbig-Haro objects related to T Tauri stars?

Correct AnswerverifiedHerbig-Haro objects are ionized gas form...View AnswerShow Answer

Electronic transitions from the H2 molecule are easily seen at

Correct AnswerverifiedShow Answer

A young protostar is ________ than the Sun even though its surface temperature is ________.

Correct AnswerverifiedShow Answer

What happens as a protostar contracts?

Correct AnswerverifiedShow Answer

Dust that is heated to 30 K will emit a blackbody spectrum that peaks near

Correct AnswerverifiedShow Answer

If you wanted to observe heavy elements in the interstellar medium, where would be the best place to look?

Correct AnswerverifiedShow Answer

The average density of the interstellar medium is

Correct AnswerverifiedShow Answer

Molecular cloud cores are places where you might find

Correct AnswerverifiedShow Answer

How long does it typically take for a protostar to form a 1 MSUN star?

Correct AnswerverifiedShow Answer

Correct Answer
verified

Correct Answer
verified

Dust in the ISM appears dark in wavelengths and bright in wavelengths.

Correct Answer
verified

Correct Answer
verified
The ISM is 99 percent gas and 1 percent ...
View Answer

Correct Answer
verified

Correct Answer
verified

Dust that glows with a peak emission wavelength of 40 $\mu$ m has a temperature of

Correct Answer
verified
B

Correct Answer
verified
The volume occupied by the Sun is given ...
View Answer

Correct Answer
verified
B

Star formation is an inefficient process, with only a few percent of the initial cloud fragment ending up as stars.This means the initial mass of a molecular cloud fragment that formed a 2 M_SUN star was probably close to

Correct Answer
verified

Correct Answer
verified
Herbig-Haro objects are ionized gas form...
View Answer

Electronic transitions from the H₂ molecule are easily seen at

Correct Answer
verified

A young protostar is than the Sun even though its surface temperature is .

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

How long does it typically take for a protostar to form a 1 M_SUN star?

Correct Answer
verified