Deck 12: Stellar Evolution

Question 1

Which of the following nuclear fuels does a one solar mass star use over the course of its entire evolution?

A) hydrogen
B) hydrogen and helium
C) hydrogen,helium,and carbon
D) hydrogen,helium,carbon,and neon
E) hydrogen,helium,carbon,neon,and oxygen

Answer 1

hydrogen and helium

Question 2

Helium fusion is called the triple alpha process because

A) the helium nucleus is known as an alpha particle.
B) it occurs very rapidly.
C) it requires a temperature three times greater than that of hydrogen fusion.
D) it is the third source of the primary fusion processes.
E) each reaction produces three carbon nuclei.

Answer 2

the helium nucleus is known as an alpha particle.

Question 3

A young star cluster will have ____ than an older star cluster.

A) a redder turn-off point
B) a bluer turn-off point
C) fewer stars
D) fewer luminous stars
E) more low mass stars

Answer 3

a bluer turn-off point

Question 4

The main sequence has a limit at the lower end because

A) low mass stars form from the interstellar medium very rarely.
B) hydrogen fusion combined 4 hydrogen nuclei to form 1 helium nucleus.
C) pressure does not depend on temperature in degenerate matter.
D) the lower limit represents when the radius of the star would be zero.
E) there is a minimum temperature for hydrogen fusion.

Question 5

In the diagram below,which point indicates the location on the HR diagram of a one solar mass star when it undergoes helium flash?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 6

Energy can flow outward from the cores of different kinds of stars by

A) conduction
B) convection
C) radiation
D) all of the above

Question 7

In the core of a main sequence star,gas pressure ____ the weight of the overlying materials.

A) is less than
B) is greater than
C) balances

Question 8

As a star like the sun exhausts hydrogen in its core,the outer layers of the star

A) become hotter and more luminous.
B) become cooler and more luminous.
C) become hotter and less luminous.
D) become cooler and less luminous.
E) become larger in radius and hotter.

Question 9

A star will experience a helium flash if

A) it is more massive than about 6 solar masses.
B) its core contains oxygen and helium.
C) its mass on the main sequence was less than 0.1 solar masses.
D) it is a supergiant.
E) its core is degenerate when helium ignites.

Question 10

What is the lifetime of a 10 star on the main sequence?

A) 3.2*10⁷ years
B) 320 years
C) 3.2*10¹² years
D) 1*10⁹ years
E) 1*10¹¹ years

Question 11

Variables of a certain type are called Cepheid variable because

A) the first one discovered was in the constellation of Cepheus.
B) they were discovered by Anna Marie Cepheid and her brother Raul.
C) they all lie in the Cepheus star cluster.
D) they can be used to determine the distance to Cepheid star clusters.
E) they can be used to determine the distance to all of the stars in the Cepheid galaxy.

Question 12

The energy emitted from the surface of a main sequence star is ____ the energy generated in the core.

A) greater than
B) less than
C) equal to

Question 13

Which of the following nuclear fuels does a 0.2 solar mass star use over the course of its entire evolution?

A) hydrogen
B) hydrogen and helium
C) hydrogen,helium,and carbon
D) hydrogen,helium,carbon,and neon
E) hydrogen,helium,carbon,neon,and oxygen

Question 14

The triple alpha process

A) controls the pulsations in Cepheid variable stars.
B) is the nuclear fusion of hydrogen to helium in massive stars.
C) is the process that produces the neutrinos we receive from the sun.
D) requires a temperature of about 5,000,000 K to operate.
E) occurs during helium flash.

Question 15

There is a mass-luminosity relation because

A) hydrogen fusion produces helium.
B) stars expand when they become giants.
C) stars support their weight by making energy.
D) the helium flash occurs in degenerate matter.
E) all stars on the main sequence have about the same radius.

Question 16

When the Cepheid variable RU Camelopardalis stopped pulsating,astronomers speculated that it was

A) exhausting its helium.
B) exhausting its hydrogen.
C) turning off its triple alpha process.
D) evolving out of the instability strip.
E) becoming a red supergiant.

Question 17

The lowest mass object that can initiate thermonuclear fusion of hydrogen has a mass of about

A) 1.
B) 60.
C) 0.5.
D) 0.08.
E) 0.001.

Question 18

Helium flash occurs

A) because helium is very explosive and cannot be controlled when the nuclear reactions occur.
B) because degenerate electrons in the core do not allow the core to expand as it heats up.
C) in Cepheid variables.
D) in stars with masses less than 0.4.
E) none of the above

Question 19

In degenerate matter

A) pressure depends only on the temperature.
B) temperature depends only on density.
C) pressure does not depend on temperature.
D) pressure does not depend on density.
E) b and c

Question 20

Giant and supergiant stars are rare because

A) they do not form as often as main sequence stars.
B) the giant and supergiant stage is unstable.
C) the giant and supergiant stage is very short.
D) helium is very rare.
E) helium flash destroys many of the stars before they can become giants and supergiants.

Question 21

A star in the instability strip pulsates because

A) the energy produced by the core is not constant.
B) the energy produced by the hydrogen burning shell is not constant.
C) the core of the star is composed of helium and degenerate electrons.
D) the surface temperature of the star is increasing.
E) density and opacity of the helium ionization zone changes with time.

Question 22

The changing period of a Cepheid variable tells us that the

A) star's luminosity is increasing.
B) surface temperature of the star is increasing.
C) hydrogen burning core has quit burning its nuclear fuel.
D) star is evolving.
E) star is about to undergo helium flash.

Question 23

What must occur for an object to be considered a main sequence star?

A) Hydrostatic equilibrium
B) Nuclear fusion reaction in the core
C) Protostar life begins
D) Both a and

Question 24

Why do nuclear fusion reactions only take place in the interior of a star?

A) The magnetic fields are strongest there.
B) The temperature is the hottest in the center.
C) The density of material is very high in the center.
D) More than one of the above.
E) FALSE; Nuclear fusion reactions can take place in the core and corona where temperatures are high enough.

Question 25

A Cepheid variable with a mass of 10 ____ than a Cepheid of 3 .

A) is less luminous
B) has a greater surface temperature
C) has a smaller radius
D) has a longer period
E) a and c

Question 26

The figure shows an HST image of the red giant star,Betelgeuse.In the red giant stage,hydrogen is being fused to helium ...

A) on the surface of the star
B) in the center of the star's helium core
C) on the outside of the star's helium core
D) Neither helium nor hydrogen is being fused in the red giant stage.

Question 27

Convection is important in stars because it

A) increases the temperature of the star.
B) mixes the gases of the star.
C) transports energy outward in the star.
D) carries the neutrinos to the surface of the star where they can escape.
E) b and c

Question 28

Star clusters are important to our study of the lives of high mass versus low mass stars because

A) stars in each cluster all formed at about the same time all with the same mass
B) the sun was once a member of a globular cluster.
C) stars in each cluster all formed at about the same time but with differing masses
D) stars in each cluster all formed at different times with differing masses
E) all of the above

Question 29

The carbon-nitrogen-oxygen cycle

A) operates at a slightly lower temperature than the proton-proton chain.
B) is most efficient in star less massive than the sun.
C) occurs when carbon and oxygen combine to form nitrogen,which produces energy.
D) produces the energy responsible for bipolar flows.
E) combines four hydrogen nuclei to form one helium nucleus,which produces energy.

Question 30

If the stars at the turnoff point of a cluster have a mass of 3 ,what is the age of the cluster?

A) 3.0*10¹⁰ years
B) 3.3*10⁹ years
C) 6.4*10⁸ years
D) 1.6*10¹¹ years
E) The age of a star cluster can not be determined from the mass of stars at the turnoff point.

Question 31

What will eventually happen to a star after its formation is most affected by its initial ...

A) speed through space.
B) oxygen content.
C) uranium content.
D) anti-matter content.
E) mass.

Question 32

RR Lyrae variables

A) are less luminous than Cepheid variables.
B) have longer periods than Cepheid variables.
C) do not have a period-luminosity relationship.
D) are eclipsing variables.
E) a and b

Question 33

Open clusters tend to be ____ than globular clusters.

A) younger and contain fewer stars
B) younger and contain more stars
C) older and contain fewer stars
D) older and contain more stars
E) more luminous and cooler

Question 34

Stars swell into giants when hydrogen is exhausted in their centers.

Question 35

It is assumed that stars in a star cluster

A) all have the same age.
B) all have the same chemical composition.
C) all have the same luminosity.
D) all of the above
E) a and b above

Question 36

Stars support their weight by generating energy in their centers.

Question 37

The helium flash is the cause of some supernovae.

Question 38

Why do higher mass stars live shorter lives on the main sequence than lower mass stars?

A) Higher mass stars burn through their nuclear fuel faster.
B) Lower mass stars don't get their energy from that same nuclear fusion source as higher mass stars.
C) Higher mass stars have less hydrogen fuel to burn.
D) Lower mass stars spend a longer time evolving to the main-sequence.
E) All of the above are false.

Question 39

What is the approximate age of the star cluster in the diagram below?

A) 2 million years
B) 2 billion years
C) 10 billion years
D) 100 billion years
E) The age of the cluster cannot be estimated from an HR diagram of the cluster.

Question 40

What characteristic of a star primarily determines its location on the main sequence?

A) age
B) distance from the galactic center
C) mass
D) space motion
E) radius

Question 41

Hydrogen fusion does not occur in stats in the giant region of the H-R diagram.

Question 42

Some massive stars only live a few million years.

Question 43

Of the stars in the instability strip,the more massive stars have longer periods and lower luminosities.

Question 44

Even in degenerate matter,pressure depends on temperature.

Question 45

The ____________________ is the thermonuclear fusion of helium to form carbon.

Question 46

Indicate the region where Cepheid variables are located in the HR diagram below.

Question 47

A gas in which the pressure no longer depends on the temperature of the gas is said to be ____________________.

Question 48

The pressure of a gas depends on the temperature and density of the gas.

Question 49

____________________ are protostars with insufficient mass to ignite nuclear fusion.

Question 50

Young star clusters have bluer turn-off points than old clusters.

Question 51

Helium fusion does not begin until the star has entered the giant region of the H-R diagram.

Question 52

Even the youngest star clusters have no stars still contracting toward the main sequence.

Question 53

Stars with masses greater than 1.1 solar masses use the ____________________ to convert hydrogen into helium and produce energy.

Question 54

The age of a star cluster can be determined from the ____________________ of the cluster.

Question 55

Giant and supergiant stars are rare because that stage is short.

Question 56

Cepheid variables can be used to determine distances because their absolute magnitude can be determined from their period.