Question 1

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

Question 2

What is the most likely explanation for the dark area in the image below?

Accepted Answer

A)  It is a region where there are no stars. 
B)  It is a region with lots of dark matter. 
C)  It is a super-massive black hole. 
D)  It is a region with thick dust blocking the starlight coming from behind. 
E)  It is a dark star cluster. 
A)  It is a region where there are no stars. 
B)  It is a region with lots of dark matter. 
C)  It is a super-massive black hole. 
D)  It is a region with thick dust blocking the starlight coming from behind. 
E)  It is a dark star cluster.

Question 3

The red emission in the photo below is due to:

Accepted Answer

A)  carbon monoxide (CO) 
B)  warm, neutral hydrogen 
C)  molecular hydrogen (H2) 
D)  ionized hydrogen (H II region) 
E)  dust 
A)  carbon monoxide (CO) 
B)  warm, neutral hydrogen 
C)  molecular hydrogen (H2) 
D)  ionized hydrogen (H II region) 
E)  dust

Question 4

The entire process of star formation is really just an evolving balance between:

Accepted Answer

A)  heat and rotation 
B)  core temperature and surface temperature 
C)  pressure and gravity 
D)  radiation and heat 
E)  luminosity and distance 
A)  heat and rotation 
B)  core temperature and surface temperature 
C)  pressure and gravity 
D)  radiation and heat 
E)  luminosity and distance

Question 5

The interstellar medium is divided up into three different kinds of gas clouds: cold gas at 10 K, warm gas at 8000 K, and hot gas at about 1 million K.

Accepted Answer

A) True 
 B)False

Question 6

Molecular hydrogen atoms are found only inside dense clouds where they are shielded from stellar radiation.

Accepted Answer

A) True 
 B)False

Question 7

When a molecular cloud fragments and stars form, the least massive stars are the first to form while the most massive stars take longer to form.

Accepted Answer

A) True 
 B)False

Question 8

Star formation in a molecular cloud can be slowed by the strength of its magnetic field and turbulence caused by supernovae and stellar winds from massive stars.

Accepted Answer

A) True 
 B)False

Question 9

Why do many stars form from a single molecular cloud?

Accepted Answer

Small density fluctuations in the parent

Question 10

Stars forming in molecular clouds tend to form first in the low-density periphery.

Accepted Answer

A) True 
 B)False

Question 11

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 12

Because angular momentum must be conserved, as a gas cloud contracts due to gravity it will also:

Accepted Answer

A)  spin slower 
B)  spin faster 
C)  increase in temperature 
D)  decrease in temperature 
E)  stay the same temperature 
A)  spin slower 
B)  spin faster 
C)  increase in temperature 
D)  decrease in temperature 
E)  stay the same temperature

Question 13

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

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 14

A _________ is a failed star that shines primarily because of energy derived from its gravitational collapse rather than nuclear burning.

Accepted Answer

A)  black hole 
B)  brown dwarf 
C)  Herbig-Haro object 
D)  protostar 
E)  T Tauri star 
A)  black hole 
B)  brown dwarf 
C)  Herbig-Haro object 
D)  protostar 
E)  T Tauri star

Question 15

Below are three pictures of the disk of the Milky Way, taken in three different wavelength ranges.   Put the three pictures in order from shortest to longest wavelength.

Accepted Answer

A)  I, II, III 
B)  II, III, I 
C)  I, III, II 
D)  II, I, III 
E)  III, I, II 
A)  I, II, III 
B)  II, III, I 
C)  I, III, II 
D)  II, I, III 
E)  III, I, II

Question 16

A protostar is usually in hydrostatic equilibrium as its collapses.

Accepted Answer

A) True 
 B)False

Question 17

Interstellar clouds are:

Accepted Answer

A)  hydrogen gas, condensed out of the interstellar medium, like water clouds in the Earth's atmosphere 
B)  regions where hydrogen tends to be denser than the surrounding gas 
C)  regions where water condenses out of the interstellar medium 
D)  oxygen gas, condensed out of the interstellar medium, like water clouds in the Earth's atmosphere 
E)  regions where hydrogen combines with oxygen to create water molecules 
A)  hydrogen gas, condensed out of the interstellar medium, like water clouds in the Earth's atmosphere 
B)  regions where hydrogen tends to be denser than the surrounding gas 
C)  regions where water condenses out of the interstellar medium 
D)  oxygen gas, condensed out of the interstellar medium, like water clouds in the Earth's atmosphere 
E)  regions where hydrogen combines with oxygen to create water molecules

Question 18

As a protostar evolves, its temperature:

Accepted Answer

A)  decreases because it is radiating 
B)  decreases because of gravitational contraction 
C)  decreases because of angular momentum 
D)  increases because of nuclear fusion 
E)  increases due to the kinetic energy of infalling material 
A)  decreases because it is radiating 
B)  decreases because of gravitational contraction 
C)  decreases because of angular momentum 
D)  increases because of nuclear fusion 
E)  increases due to the kinetic energy of infalling material

Question 19

Describe the general process of how the interstellar medium can create a star.

Accepted Answer

Deep inside of a cold, molecular cloud,

Question 20

Why can we see dust in the interstellar medium better at far-infrared wavelengths than we can at optical wavelengths?

Accepted Answer

Because the dust is cold at te

Exam 15: Star Formation and the Interstellar Medium

What happens as a protostar contracts?

What is the most likely explanation for the dark area in the image below?

The red emission in the photo below is due to:

The entire process of star formation is really just an evolving balance between:

The interstellar medium is divided up into three different kinds of gas clouds: cold gas at 10 K, warm gas at 8000 K, and hot gas at about 1 million K.

Molecular hydrogen atoms are found only inside dense clouds where they are shielded from stellar radiation.

When a molecular cloud fragments and stars form, the least massive stars are the first to form while the most massive stars take longer to form.

Star formation in a molecular cloud can be slowed by the strength of its magnetic field and turbulence caused by supernovae and stellar winds from massive stars.

Why do many stars form from a single molecular cloud?

Stars forming in molecular clouds tend to form first in the low-density periphery.

Magnetic fields inside a molecular cloud act to:

Because angular momentum must be conserved, as a gas cloud contracts due to gravity it will also:

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

A _________ is a failed star that shines primarily because of energy derived from its gravitational collapse rather than nuclear burning.

Below are three pictures of the disk of the Milky Way, taken in three different wavelength ranges. Put the three pictures in order from shortest to longest wavelength.

A protostar is usually in hydrostatic equilibrium as its collapses.

Interstellar clouds are:

As a protostar evolves, its temperature:

Describe the general process of how the interstellar medium can create a star.

Why can we see dust in the interstellar medium better at far-infrared wavelengths than we can at optical wavelengths?

Why Learn Astronomy

Patterns in the Skymotions of Earth

Motion of Astronomical Bodies

Gravity and Orbits

Light

The Tools of the Astronomer

The Birth and Evolution of Planetary Systems

The Terrestrial Planets and Earths Moon

Atmospheres of the Terrestrial Planets

Worlds of Gas and Liquid the Giant Planets

Planetary Adornmentsmoons 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

The Expanding Universe

Galaxies

The Milky Waya Normal Spiral Galaxy

Modern Cosmology

Large-Scale Structure in the Universe

Life

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