Question 1

What are the letters that follow the spectral sequence OBAFGKM?

Accepted Answer

A) NP 
B) YZ 
C) LT 
D) CD 
E) UV 
A) NP 
B) YZ 
C) LT 
D) CD 
E) UV

Question 2

Protostars start off more luminous than the main sequence stars they become.

Accepted Answer

A) True 
 B)False

Question 3

Process of Science: The existence of brown dwarfs was predicted for decades before their discovery in 1995.Why did it take so long?

Accepted Answer

Brown dwarfs are very faint,especially a

Question 4

Interstellar dust consists mostly of

Accepted Answer

A) ozone "smog." 
B) microscopic particles of carbon and silicon. 
C) hydrogen and helium atoms. 
D) tiny grains of water ice. 
E) the same tiny particles found in household dust. 
A) ozone "smog." 
B) microscopic particles of carbon and silicon. 
C) hydrogen and helium atoms. 
D) tiny grains of water ice. 
E) the same tiny particles found in household dust.

Question 5

Briefly describe how a star forms.

Accepted Answer

In cold,dense molecular clouds,gravity b

Question 6

In any star cluster,stars with lower masses greatly outnumber those with higher masses.

Accepted Answer

A) True 
 B)False

Question 7

Which of the following statements about brown dwarfs is not true?

Accepted Answer

A) Brown dwarfs eventually collapse to become white dwarfs. 
B) Brown dwarfs are supported against gravity by degeneracy pressure,which does not depend on the object's temperature. 
C) Brown dwarfs form like ordinary stars but are too small to sustain nuclear fusion in their cores. 
D) All brown dwarfs have masses less than about 8% that of our Sun. 
A) Brown dwarfs eventually collapse to become white dwarfs. 
B) Brown dwarfs are supported against gravity by degeneracy pressure,which does not depend on the object's temperature. 
C) Brown dwarfs form like ordinary stars but are too small to sustain nuclear fusion in their cores. 
D) All brown dwarfs have masses less than about 8% that of our Sun.

Question 8

The typical size of an interstellar dust grain is

Accepted Answer

A) 1 angstrom. 
B) 1 nanometer. 
C) 1 micrometer. 
D) 1 millimeter. 
E) 1 centimeter. 
A) 1 angstrom. 
B) 1 nanometer. 
C) 1 micrometer. 
D) 1 millimeter. 
E) 1 centimeter.

Question 9

Most stars are born in clusters containing thousands of stars.

Accepted Answer

A) True 
 B)False

Question 10

How long does the protostellar stage last for a star like our Sun?

Accepted Answer

A) 1 million years 
B) 3 million years 
C) 10 million years 
D) 30 million years 
E) 100 million years 
A) 1 million years 
B) 3 million years 
C) 10 million years 
D) 30 million years 
E) 100 million years

Question 11

Process of Science: Astronomers have not found any stars without some heavy elements.How does this constrain theories for the formation of the first generation of stars in the Universe?

Accepted Answer

The first stars that formed must have li

Question 12

By mass,the interstellar medium in our region of the Milky Way consists of

Accepted Answer

A) 70% Hydrogen,30% Helium. 
B) 70% Hydrogen,28% Helium,2% heavier elements. 
C) 70% Hydrogen,20% Helium,10% heavier elements. 
D) 50% Hydrogen,50% Helium. 
E) 50% Hydrogen,30% Helium,20% heavier elements. 
A) 70% Hydrogen,30% Helium. 
B) 70% Hydrogen,28% Helium,2% heavier elements. 
C) 70% Hydrogen,20% Helium,10% heavier elements. 
D) 50% Hydrogen,50% Helium. 
E) 50% Hydrogen,30% Helium,20% heavier elements.

Question 13

What percentage of a molecular cloud's mass is interstellar dust?

Accepted Answer

A) 1% 
B) 2% 
C) 28% 
D) 50% 
E) 1-50%,depending on the mass of the molecular cloud 
A) 1% 
B) 2% 
C) 28% 
D) 50% 
E) 1-50%,depending on the mass of the molecular cloud

Question 14

Jupiter is a failed star.

Accepted Answer

A) True 
 B)False

Question 15

What is the eventual fate of a brown dwarf?

Accepted Answer

A) It remains the same forever. 
B) It gradually cools down and becomes ever dimmer. 
C) It gradually contracts and heats up until nuclear fusion ignites in its interior and it becomes a faint star. 
D) It becomes ever denser and hotter until it becomes a white dwarf. 
E) Gravity ultimately "wins" and it becomes a small black hole. 
A) It remains the same forever. 
B) It gradually cools down and becomes ever dimmer. 
C) It gradually contracts and heats up until nuclear fusion ignites in its interior and it becomes a faint star. 
D) It becomes ever denser and hotter until it becomes a white dwarf. 
E) Gravity ultimately "wins" and it becomes a small black hole.

Question 16

Suppose you look by eye at a star near the edge of a dusty interstellar cloud.The star will look ________ than it would if it were outside the cloud.

Accepted Answer

A) dimmer and bluer 
B) more redshifted 
C) brighter and redder 
D) dimmer and redder 
A) dimmer and bluer 
B) more redshifted 
C) brighter and redder 
D) dimmer and redder

Question 17

The most abundant molecule in molecular clouds is

Accepted Answer

A) H₂. 
B) He₂. 
C) CO. 
D) H₂O. 
E) HHe. 
A) H₂. 
B) He₂. 
C) CO. 
D) H₂O. 
E) HHe.

Question 18

Consider a large molecular cloud that will give birth to a cluster of stars.Which of the following would you expect to be true?

Accepted Answer

A) All the stars in the cluster will be of about the same mass. 
B) A few massive stars will form,live,and die before the majority of the star's clusters even complete their protostar stage. 
C) All the stars in the cluster will become main-sequence stars at about the same time. 
D) All the stars in the cluster will have approximately the same luminosity and surface temperature. 
A) All the stars in the cluster will be of about the same mass. 
B) A few massive stars will form,live,and die before the majority of the star's clusters even complete their protostar stage. 
C) All the stars in the cluster will become main-sequence stars at about the same time. 
D) All the stars in the cluster will have approximately the same luminosity and surface temperature.

Question 19

What is interstellar reddening and explain how it can be used to map out the distribution of dust in a cloud.

Accepted Answer

Short wavelength (blue)light passing thr

Question 20

Which of the following types of molecule is the most abundant in an interstellar molecular cloud?

Accepted Answer

A) CO 
B) H₂O 
C) H₂ 
D) NH₃ 
A) CO 
B) H₂O 
C) H₂ 
D) NH₃

Exam 16: Star Birth

What are the letters that follow the spectral sequence OBAFGKM?

Protostars start off more luminous than the main sequence stars they become.

Process of Science: The existence of brown dwarfs was predicted for decades before their discovery in 1995.Why did it take so long?

Interstellar dust consists mostly of

Briefly describe how a star forms.

In any star cluster,stars with lower masses greatly outnumber those with higher masses.

Which of the following statements about brown dwarfs is not true?

The typical size of an interstellar dust grain is

Most stars are born in clusters containing thousands of stars.

How long does the protostellar stage last for a star like our Sun?

Process of Science: Astronomers have not found any stars without some heavy elements.How does this constrain theories for the formation of the first generation of stars in the Universe?

By mass,the interstellar medium in our region of the Milky Way consists of

What percentage of a molecular cloud's mass is interstellar dust?

Jupiter is a failed star.

What is the eventual fate of a brown dwarf?

Suppose you look by eye at a star near the edge of a dusty interstellar cloud.The star will look ________ than it would if it were outside the cloud.

The most abundant molecule in molecular clouds is

Consider a large molecular cloud that will give birth to a cluster of stars.Which of the following would you expect to be true?

What is interstellar reddening and explain how it can be used to map out the distribution of dust in a cloud.

Which of the following types of molecule is the most abundant in an interstellar molecular cloud?

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