Question 1

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

Question 2

If a 1 M $\odot$ protostar starts out on the Hayashi track with a temperature of 3300 K and a luminosity of 320 L $\odot$ , what is its approximate radius?

Accepted Answer

A)  25 R $\odot$ 
B)  55 R $\odot$ 
C)  75 R $\odot$ 
D)  105 R $\odot$ 
E)  125 R $\odot$ 
A)  25 R $\odot$ 
B)  55 R $\odot$ 
C)  75 R $\odot$ 
D)  105 R $\odot$ 
E)  125 R $\odot$

Question 3

Compare the volume of the Sun with the volume of interstellar space it occupies. 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 4

What primarily makes it difficult to observe protostars?

Accepted Answer

A)  They occur in dusty regions. 
B)  They have low luminosities. 
C)  They do not shine at any wavelength until they become T Tauri stars. 
D)  The star formation process happens so quickly. 
E)  They are too small to be seen. 
A)  They occur in dusty regions. 
B)  They have low luminosities. 
C)  They do not shine at any wavelength until they become T Tauri stars. 
D)  The star formation process happens so quickly. 
E)  They are too small to be seen.

Question 5

Figure 1
-Use Figure 1 to complete the following statement. A low-mass protostar remains roughly constant in _________ and decreases in _________ as it follows its evolutionary track.

Accepted Answer

A)  temperature; luminosity 
B)  radius; temperature 
C)  luminosity; radius 
D)  luminosity; temperature 
E)  radius; luminosity 
A)  temperature; luminosity 
B)  radius; temperature 
C)  luminosity; radius 
D)  luminosity; temperature 
E)  radius; luminosity

Question 6

The most common types of stars in our galaxy are:

Accepted Answer

A)  high-mass stars 
B)  low-mass stars 
C)  an equal mix of high- and low-mass stars 
D)  low-mass stars near the Sun and high-mass stars far away 
E)  We do not yet know which types of stars are most common in our galaxy. 
A)  high-mass stars 
B)  low-mass stars 
C)  an equal mix of high- and low-mass stars 
D)  low-mass stars near the Sun and high-mass stars far away 
E)  We do not yet know which types of stars are most common in our galaxy.

Question 7

In the interstellar medium, molecules survive only in regions with:

Accepted Answer

A)  low temperatures 
B)  high densities 
C)  lots of dust 
D)  all of the above 
A)  low temperatures 
B)  high densities 
C)  lots of dust 
D)  all of the above

Question 8

For an object in hydrostatic equilibrium, if the temperature inside the object were to increase, the object would:

Accepted Answer

A)  expand 
B)  contract 
C)  implode 
D)  remain the same size 
E)  explode 
A)  expand 
B)  contract 
C)  implode 
D)  remain the same size 
E)  explode

Question 9

We detect neutral gas in the interstellar medium by looking for radiation at 21 cm that arises when:

Accepted Answer

A)  an electron moves from the n = 1 to n = 2 state in a hydrogen atom 
B)  an electron is ionized from a hydrogen atom 
C)  carbon monoxide (CO) gas is excited by stellar radiation 
D)  the spin of an electron flips and aligns with the spin of a proton in a hydrogen atom 
E)  an electron combines with a proton to make a hydrogen atom 
A)  an electron moves from the n = 1 to n = 2 state in a hydrogen atom 
B)  an electron is ionized from a hydrogen atom 
C)  carbon monoxide (CO) gas is excited by stellar radiation 
D)  the spin of an electron flips and aligns with the spin of a proton in a hydrogen atom 
E)  an electron combines with a proton to make a hydrogen atom

Question 10

Which of the following traits does NOT help slow or prevent the collapse of a gas cloud?

Accepted Answer

A)  high mass 
B)  high temperature 
C)  turbulence 
D)  magnetic fields 
E)  angular momentum 
A)  high mass 
B)  high temperature 
C)  turbulence 
D)  magnetic fields 
E)  angular momentum

Question 11

At what wavelength are H II regions most clearly visible, and why do H II regions mark the regions where new stars are currently being formed?

Accepted Answer

H II regions are best seen at H-alpha wi

Question 12

The lowest-density gas in the interstellar medium is also the coldest.

Accepted Answer

A) True 
 B)False

Question 13

Herbig-Haro objects are almost always found in pairs on either side of a young protostar.

Accepted Answer

A) True 
 B)False

Question 14

In the densest molecular clouds, the average density is approximately 300 atoms/cm3. If a cube of molecular cloud gas with this density contained 100 M$\odot$ of material (the amount needed to make a 1 M$\odot$ star), what would be the length of a side of the cube in units of AU? For reference, the mass of the Sun is 2 * 1030 kg, the mass of a hydrogen atom is 1.7 *10 - 27 kg, and 1 AU = 1.5 * 1011 m.

Accepted Answer

If the one side of the cube has length X

Question 15

The H- ion is very important in protostars because it:

Accepted Answer

A)  reacts with oxygen to produce water 
B)  undergoes fusion and produces energy 
C)  helps make the protostars denser 
D)  acts as a temperature regulator 
E)  reduces angular momentum 
A)  reacts with oxygen to produce water 
B)  undergoes fusion and produces energy 
C)  helps make the protostars denser 
D)  acts as a temperature regulator 
E)  reduces angular momentum

Question 16

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 17

An H II region signals the presence of:

Accepted Answer

A)  newly formed stars 
B)  young stars 
C)  ionized hydrogen gas 
D)  O- and B-type stars 
E)  all of the above 
A)  newly formed stars 
B)  young stars 
C)  ionized hydrogen gas 
D)  O- and B-type stars 
E)  all of the above

Question 18

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

Accepted Answer

A)  1 $\mu$m 
B)  30 $\mu$m 
C)  50 $\mu$m 
D)  100 $\mu$m 
E)  500 $\mu$m 
A)  1 $\mu$m 
B)  30 $\mu$m 
C)  50 $\mu$m 
D)  100 $\mu$m 
E)  500 $\mu$m

Question 19

Figure 1
-Use Figure 1 to complete the following statement. A high-mass protostar remains roughly constant in _________ and increases in _________ as it follows its evolutionary track.

Accepted Answer

A)  temperature; luminosity 
B)  radius; temperature 
C)  luminosity; radius 
D)  luminosity; temperature 
E)  radius; luminosity 
A)  temperature; luminosity 
B)  radius; temperature 
C)  luminosity; radius 
D)  luminosity; temperature 
E)  radius; luminosity

Question 20

"Weather" in the interstellar medium is produced:

Accepted Answer

A)  only by supernovae 
B)  by supernovae and strong winds from luminous stars 
C)  by supernovae, strong winds from luminous stars, and fast-moving stars 
D)  by supernovae, strong winds from luminous stars, fast-moving stars, and exploding planets 
E)  by supernovae, strong winds from luminous stars, fast-moving stars, exploding planets, and black holes 
A)  only by supernovae 
B)  by supernovae and strong winds from luminous stars 
C)  by supernovae, strong winds from luminous stars, and fast-moving stars 
D)  by supernovae, strong winds from luminous stars, fast-moving stars, and exploding planets 
E)  by supernovae, strong winds from luminous stars, fast-moving stars, exploding planets, and black holes

Exam 15: Star Formation and the Interstellar Medium

Molecular cloud cores are places where you might find:

If a 1 M ⊙\odot⊙ protostar starts out on the Hayashi track with a temperature of 3300 K and a luminosity of 320 L ⊙\odot⊙ , what is its approximate radius?

What primarily makes it difficult to observe protostars?

Figure 1 -Use Figure 1 to complete the following statement. A low-mass protostar remains roughly constant in _________ and decreases in _________ as it follows its evolutionary track.

The most common types of stars in our galaxy are:

In the interstellar medium, molecules survive only in regions with:

For an object in hydrostatic equilibrium, if the temperature inside the object were to increase, the object would:

We detect neutral gas in the interstellar medium by looking for radiation at 21 cm that arises when:

Which of the following traits does NOT help slow or prevent the collapse of a gas cloud?

At what wavelength are H II regions most clearly visible, and why do H II regions mark the regions where new stars are currently being formed?

The lowest-density gas in the interstellar medium is also the coldest.

Herbig-Haro objects are almost always found in pairs on either side of a young protostar.

The H- ion is very important in protostars because it:

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

An H II region signals the presence of:

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

Figure 1 -Use Figure 1 to complete the following statement. A high-mass protostar remains roughly constant in _________ and increases in _________ as it follows its evolutionary track.

"Weather" in the interstellar medium is produced:

Why Learn Astronomy

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Motion of Astronomical Bodies

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Taking the Measure of Stars

Our Starthe Sun

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Evolution of High-Mass Stars

Relativity and Black Holes

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Galaxies

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Modern Cosmology

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If a 1 M _$\odot$ protostar starts out on the Hayashi track with a temperature of 3300 K and a luminosity of 320 L _$\odot$ , what is its approximate radius?

Figure 1 -Use Figure 1 to complete the following statement. A low-mass protostar remains roughly constant in _ and decreases in _ as it follows its evolutionary track.

The H^- ion is very important in protostars because it:

Figure 1 -Use Figure 1 to complete the following statement. A high-mass protostar remains roughly constant in _ and increases in _ as it follows its evolutionary track.