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

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

Answer 2

in the Orion Nebula

Question 3

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

Answer 3

the fusion of hydrogen

Question 4

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 5

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

Question 6

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 7

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 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

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 11

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

Question 12

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

Question 13

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

Question 14

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 15

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 16

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

Question 17

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

Question 18

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 19

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 20

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 21

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 22

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 23

What istheresistanceofagastotheflowofradiation?

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

Question 25

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

Question 26

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

Question 27

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

Question 28

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

Question 29

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

Question 30

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 31

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

Question 32

Briefly describe the pressure-temperature thermostat in stars.

Question 33

Whatis a protostar and how does it get its energy?

Question 34

Hydrostatic equilibrium is the balance between _____________ and radiation _____________.

Question 35

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

Question 36

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

Question 37

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

Question 38

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

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

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 41

List three processes energy can be transported between regions.

Question 42

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

Question 43

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

Question 44

Theforce responsible for the collapse of an interstellar cloud is_____________.