Question 1

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

Accepted Answer

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

Question 2

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 3

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. 
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. B

Question 4

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

Question 5

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

Question 6

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

Question 7

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

Question 8

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)  radio 
A)  X-ray 
B)  ultraviolet 
C)  optical 
D)  infrared 
E)  radio

Question 9

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

Accepted Answer

The ISM is 99 percent gas and 1 percent

Question 10

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

Question 11

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

Question 12

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. 
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.

Question 13

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. 
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.

Question 14

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 15

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

Accepted Answer

Herbig-Haro objects are ionized gas form

Question 16

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

Question 17

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. 
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.

Question 18

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 these 
A)  protostars. 
B)  Herbig-Haro objects. 
C)  molecular hydrogen (H2). 
D)  carbon monoxide (CO). 
E)  all of these

Question 19

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; infrared 
A)  visible; ultraviolet 
B)  infrared; radio 
C)  infrared; visible 
D)  radio; ultraviolet 
E)  visible; infrared

Question 20

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

Exam 15: The Interstellar Medium and Star Formation

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

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?

Stars forming in molecular clouds tend to form first in

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

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

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

The average density of the interstellar medium is

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

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

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

What happens as a protostar contracts?

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

Bipolar outflows create bright bow shocks because

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

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

Magnetic fields inside a molecular cloud act to

Molecular cloud cores are places where you might find

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

Electronic transitions from the H2 molecule are easily seen at

Thinking Like an Astronomer

Patterns in the Skymotions of Earth and the Moon

Motion of Astronomical Bodies

Gravity and Orbits

Light

The Tools of the Astronomer

The Formation of Planetary Systems

The Terrestrial Planets and Earths Moon

Atmospheres of the Terrestrial Planets

Worlds of Gas and Liquidthe Giant Planets

Planetary Moons and Rings

Dwarf Planets and Small Solar System Bodies

Taking the Measure of Stars

Our Starthe Sun

Evolution of Low-Mass Stars

Evolution of High-Mass Stars

Relativity and Black Holes

Galaxies

The Milky Waya Normal Spiral Galaxy

The Expanding Universe

Cosmology

Large-Scale Structure in the Universe

Life

Filters

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

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

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

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

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

Electronic transitions from the H₂ molecule are easily seen at