Question 1

If you could watch stars forming out of a gas cloud,which stars would form first?

Accepted Answer

A) low-mass stars 
B) medium-mass stars 
C) high-mass stars 
D) stars with low temperatures 
E) stars with more heavy elements 
A) low-mass stars 
B) medium-mass stars 
C) high-mass stars 
D) stars with low temperatures 
E) stars with more heavy elements

Question 2

The dust in the interstellar medium comes primarily from the stellar winds of main-sequence stars.

Accepted Answer

A) True 
 B)False

Question 3

The figures below show the spectrum of a star,along with five other spectra labeled A through E.   Which one of the labeled spectra shows what the spectrum of that star would look like if it were viewed through a significant amount of interstellar dust?

Accepted Answer

A) A 
B) B 
C) C 
D) D 
E) E 
A) A 
B) B 
C) C 
D) D 
E) E

Question 4

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 5

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 6

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 7

When a 3 M⨀ protostar forms,it starts out at the top of the Hayashi track with a luminosity of 4,000 L⨀ and a temperature of 3600 K.What is its radius at this point (give the answer in units of R⨀),and how many times larger is it at this stage compared to its radius as a main-sequence star,which is about 2.5 R⨀? For reference,the Sun's temperature is 5800 K.

Accepted Answer

The Stefan-Boltzmann law says

Question 8

Why does the surface temperature of a low-mass protostar remain nearly constant as its core contracts?

Accepted Answer

It remains nearly constant bec

Question 9

When radiation from an object passes through the interstellar medium:

Accepted Answer

A) the object appears dimmer 
B) the object appears bluer 
C) the object appears bluer and dimmer 
D) the object appears redder and dimmer 
E) the object's apparent velocity changes 
A) the object appears dimmer 
B) the object appears bluer 
C) the object appears bluer and dimmer 
D) the object appears redder and dimmer 
E) the object's apparent velocity changes

Question 10

Which of the following stars spend the longest time on their Hayashi tracks?

Accepted Answer

A) 100 M⨀ stars 
B) 10 M⨀ stars 
C) 1 M⨀ stars 
D) 0.1 M⨀ stars 
E) 0.08 M⨀ stars 
A) 100 M⨀ stars 
B) 10 M⨀ stars 
C) 1 M⨀ stars 
D) 0.1 M⨀ stars 
E) 0.08 M⨀ stars

Question 11

A typical molecular cloud has a temperature of approximately:

Accepted Answer

A) 0.3 K 
B) 10 K 
C) 80 K 
D) 300 K 
E) 1000 K 
A) 0.3 K 
B) 10 K 
C) 80 K 
D) 300 K 
E) 1000 K

Question 12

The H- atom is important in protostars because it acts as a powerful temperature regulator.

Accepted Answer

A) True 
 B)False

Question 13

The coldest molecular clouds in our galaxy have temperatures of approximately 1000 K.

Accepted Answer

A) True 
 B)False

Question 14

"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

Question 15

Why do many stars form from a single molecular cloud?

Accepted Answer

Small density fluctuations in the parent

Question 16

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 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

How are H II regions and the hot intercloud gas heated?

Accepted Answer

Hot intercloud gas is heated b

Question 19

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

Accepted Answer

A) True 
 B)False

Question 20

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

Accepted Answer

A) 25 R⨀ 
B) 55 R⨀ 
C) 75 R⨀ 
D) 105 R⨀ 
E) 125 R⨀ 
A) 25 R⨀ 
B) 55 R⨀ 
C) 75 R⨀ 
D) 105 R⨀ 
E) 125 R⨀

Exam 15: Star Formation and the Interstellar Medium

If you could watch stars forming out of a gas cloud,which stars would form first?

The dust in the interstellar medium comes primarily from the stellar winds of main-sequence stars.

The figures below show the spectrum of a star,along with five other spectra labeled A through E. Which one of the labeled spectra shows what the spectrum of that star would look like if it were viewed through a significant amount of interstellar dust?

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

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?

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

Why does the surface temperature of a low-mass protostar remain nearly constant as its core contracts?

When radiation from an object passes through the interstellar medium:

Which of the following stars spend the longest time on their Hayashi tracks?

A typical molecular cloud has a temperature of approximately:

The H- atom is important in protostars because it acts as a powerful temperature regulator.

The coldest molecular clouds in our galaxy have temperatures of approximately 1000 K.

"Weather" in the interstellar medium is produced:

Why do many stars form from a single molecular cloud?

The red emission in the photo below is due to:

Magnetic fields inside a molecular cloud act to:

How are H II regions and the hot intercloud gas heated?

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

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

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 Adornments 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

The Expanding Universe

Galaxies

The Milky Waya Normal Spiral Galaxy

Modern Cosmology

Large-Scale Structure in the Universe

Life

Filters

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

The H^- atom is important in protostars because it acts as a powerful temperature regulator.

If a 1 M_⨀protostar starts out on the Hayashi track with a temperature of 3300 K and a luminosity of 320 L_⨀,what is its approximate radius?