Question 1

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 C

Question 2

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 B

Question 3

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

Accepted Answer

A) True 
 B)False  False

Question 4

How long does it typically take for a protostar to form a 1 M⨀ 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 5

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 6

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

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 7

We observe neutral hydrogen gas using 21-cm emission.

Accepted Answer

A) True 
 B)False

Question 8

Why does a protostar continue to collapse as it is forming?

Accepted Answer

It continually radiates away t

Question 9

Some molecular clouds have so much internal pressure that it exceeds their self-gravity.What keeps them from expanding and dissipating?

Accepted Answer

The pressure of the external i

Question 10

The source of energy for a contracting protostar comes from:

Accepted Answer

A) thermonuclear energy 
B) kinetic energy 
C) chemical energy 
D) gravitational potential energy 
E) radiation energy 
A) thermonuclear energy 
B) kinetic energy 
C) chemical energy 
D) gravitational potential energy 
E) radiation energy

Question 11

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 12

The average density of the interstellar medium is:

Accepted Answer

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

Question 13

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 14

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

Accepted Answer

The ISM is

Question 15

Given the low efficiency of the star formation process,the initial mass of a molecular cloud fragment that formed a 2 M⨀ star was probably close to:

Accepted Answer

A) 10 M⨀ 
B) 50 M⨀ 
C) 100 M⨀ 
D) 500 M⨀ 
E) 1,000 M⨀ 
A) 10 M⨀ 
B) 50 M⨀ 
C) 100 M⨀ 
D) 500 M⨀ 
E) 1,000 M⨀

Question 16

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 17

What critical event transforms a protostar into a normal main-sequence star?

Accepted Answer

A) Planets form in the accretion disk. 
B) The star grows suddenly larger in radius. 
C) Triple alpha reactions begin in the core. 
D) Nuclear fusion begins in the core. 
E) Convection begins throughout the star's interior. 
A) Planets form in the accretion disk. 
B) The star grows suddenly larger in radius. 
C) Triple alpha reactions begin in the core. 
D) Nuclear fusion begins in the core. 
E) Convection begins throughout the star's interior.

Question 18

The average density of the interstellar medium is many times less dense than the best vacuum on Earth.

Accepted Answer

A) True 
 B)False

Question 19

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

Question 20

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

Exam 15: Star Formation and the Interstellar Medium

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

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

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

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

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

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

We observe neutral hydrogen gas using 21-cm emission.

Why does a protostar continue to collapse as it is forming?

Some molecular clouds have so much internal pressure that it exceeds their self-gravity.What keeps them from expanding and dissipating?

The source of energy for a contracting protostar comes from:

What primarily makes it difficult to observe protostars?

The average density of the interstellar medium is:

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

Given the low efficiency of the star formation process,the initial mass of a molecular cloud fragment that formed a 2 M⨀ star was probably close to:

Molecular cloud cores are places where you might find:

What critical event transforms a protostar into a normal main-sequence star?

The average density of the interstellar medium is many times less dense than the best vacuum on Earth.

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

As a protostar evolves,its temperature:

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

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

Given the low efficiency of the star formation process,the initial mass of a molecular cloud fragment that formed a 2 M_⨀ star was probably close to: