Deck 11: Formation and Structure of Stars

Question 1

Convection is important in stars because it transports energy outward in the star.

Answer 1

True

Question 2

The Sun, a one solar mass star, will take approximately how many years to go from protostar to main sequence star?

A) 160,000 years
B) 700,000 years
C) 8 million years
D) 30 million years
E) 100 million years

Answer 2

D

Question 3

When a large gas cloud starts to collapse in a free-fall due to gravity, the cloud will ____.

A) increase in temperature
B) decrease in temperature
C) rotate slower
D) remain at the same temperature
E) become unstable and breakup

Answer 3

A

Question 4

Where is the Trapezium found?

A) in the constellation Trapium
B) in the Orion Nebula
C) in all protostars
D) in all cocoon nebulae
E) in the Bok globules

Question 5

When a large gas cloud starts to collapse in a free-fall due to gravity, it will start to cool down as it contracts because of the atoms fall inward.

Question 6

Four of following are factors that must be overcome by a large molecular cloud before gravitational contraction can begin. Which one is the exception?

A) thermal energy of the gas
B) magnetic field of the ISM
C) rotation of the gas cloud
D) intense radiation from a nearby star
E) turbulence in the ISM

Question 7

After a protostar has progressed in its development, it will have a dense inner part and an outer envelope called a(n) ____.

A) outer-protostar
B) Bok globules
C) upper proto-sphere
D) cocoon nebulae
E) planetary nebulae

Question 8

One of the major star forming regions in space is the Orion Nebula.

Question 9

One of the factors that a large molecular cloud must overcome in order for gravitational contraction to begin is the thermal energy of the gas.

Question 10

The temperature at the core of a star must be at least 1 million degrees Kelvin before fusion can begin.

Question 11

Low mass stars like the Sun transport energy near their surface using convection.

Question 12

Eighty percent of the stars on the H-R Diagram are on the main sequence, and that is because the star is in hydrostatic equilibrium due to the _____.

A) degenerate property of hydrogen
B) degenerate property of helium
C) Hertzsprung-Russell Principle
D) fusion of hydrogen
E) fusion of helium

Question 13

As the protostar contracts gravitationally, it will rotate faster and faster and produce a(n) ____.

A) protostellar globular
B) young stellar object (YSO)
C) protostellar envelope
D) cocoon nebula
E) protostellar disk

Question 14

A protostar will continue to collapse due to gravity until it reaches the main sequence, and then gravitational collapse will stop when _____ begins.

A) the formation of star-globulars
B) atoms degenerate at the core of the star
C) the fusion of hydrogen
D) the fusion of helium
E) the fission of hydrogen

Question 15

Which trigger could start the gravitational contraction of a molecular cloud?

A) a faster rotation of the molecular cloud
B) an intense magnetic field
C) the collision of molecular clouds
D) intense radiation from a nearby star
E) a nearby spectral type G star

Question 16

Stellar winds and _____ will eventually blow away the protostellar disk and remnant cocoons of a protostar apart.

A) gas jets
B) magnetic fields
C) shock waves
D) radiation pressure
E) gravity waves

Question 17

Main sequence O stars have convective cores because they fuse hydrogen in the proton-proton chain.

Question 18

One of the factors that a large molecular cloud must overcome in order for gravitational contraction to begin is rotation of the gas cloud.

Question 19

The proton-proton chain for fusing hydrogen into helium is a much more complicated process than the CNO Cycle for fusing hydrogen into helium.

Question 20

One trigger that could start the gravitational contraction of a molecular cloud to form stars is a passing shock wave.

Question 21

What istheresistanceofagastotheflowofradiation?

A) degeneracy
B) conduction
C) opacity
D) hydrostatic pressure
E) gravitational pressure

Question 22

How do large mass stars in the upper region of the main sequence produce energy?

A) by fusing hydrogen using the proton-proton chain
B) by fusing hydrogen using the CNO Cycle (carbon-nitrogen-oxygen)
C) by fusing hydrogen using both the CNO Cycle and the proton-proton chain
D) by fusing hydrogen using the HNO Cycle (hydrogen-nitrogen-oxygen)
E) by fusing helium using the HeNO Cycle (helium-nitrogen-oxygen)

Question 24

What is the difference between the proton-proton chain and the CNO cycle?

Question 25

Stars with masses equal to or less than 1.1 solar masses use the _____________ to convert H into He for their energy source.

Question 26

Describe the concept of a "birth line" and identify where it falls on the H-R Diagram.

Question 27

Hydrostatic equilibrium in a newborn star is regulated by a very unique thermostat called the _____________ thermostat.

Question 28

During the main sequence lifetime of a star of any mass, the core of the star will be composed mainly of ____.

A) hydrogen
B) helium
C) carbon
D) hydrogen and helium
E) helium and carbon

Question 29

List three processes energy can be transported between regions.

Question 30

Before a giant molecular cloud can contract gravitationally, it must overcome four physical factors that resist compression.  What are these four factors?

Question 31

Hydrostatic equilibrium is the balance between _____________ and radiation _____________.

Question 32

Theforce responsible for the collapse of an interstellar cloud is_____________.

Question 33

Energy flows by radiation or convection inside normal stars but almost never by _____________ because radiation or convection is much more efficient.

Question 34

Pre-main sequence stars (not protostars) on the H-R Diagram are _____.

A) above and to the right of supergiants
B) below and to the left of the main sequence
C) below and to the left of white dwarfs
D) above and to the right of the main sequence
E) not on the H-R Diagram yet

Question 35

The nuclear reactions in a star's core burn steadily so long as the relationship between _____________ and_____________ is stable.

Question 36

Briefly describe the pressure-temperature thermostat in stars.

Question 37

How do low mass stars in the lower region of the main sequence produce their energy?

A) by fusing hydrogen using the proton-proton chain
B) by fusing hydrogen using the CNO Cycle (carbon-nitrogen-oxygen)
C) by fusing hydrogen using both the CNO Cycle and the proton-proton chain
D) by fusing hydrogen using the HNO Cycle (hydrogen-nitrogen-oxygen)
E) by fusing helium using the HeNO Cycle (helium-nitrogen-oxygen)

Question 38

Star clusters are important to the study the stellar evolution because stars in a given cluster have the same _____________.

Question 39

When a large gas cloud starts to collapse in a free-fall due to gravity, the temperature of the gas will _____________.

Question 40

When a large gas cloud starts to collapse in a free-fall due to gravity, the rotation rate will ______________.

Question 41

How does a gas cloud become hot enough to ignite nuclear reactions?

Question 42

Whatis a protostar and how does it get its energy?

Question 43

There are several triggers that could start the gravitational contraction of a molecular cloud and subsequent star formation.  List two of these triggers.

Question 44

The proton-proton chain needs a high temperature because the protons must overcome the _____________.