Deck 20: Stellar Evolution: The Life and Death of a Star

Question 1

While none yet exist,in the very distant future,black dwarfs will comprise the majority of the "normal matter" of the universe.

Answer 1

True

Question 2

Eventually,all low mass stars will become white,then black,dwarfs.

Answer 2

True

Question 3

Evolution of a star off the main sequence is caused by the loss of mass from hydrogen fusion by the star while a main sequence star.

Answer 3

False

Question 4

The shell ejection in making a planetary is spherical and symmetrical in all cases.

Question 5

The matter in white dwarfs is about a million times denser than matter around you,since you have packed the mass of the Sun into the volume of our Earth.

Question 6

Modern astronomers have observed the complete life cycle for many stars,making stellar evolution one of the best-tested astronomical theories.

Question 7

Every red dwarf star that ever joined the main sequence is still there today.

Question 8

There is no helium flash for a high mass star; for them,it is just one more step toward the heaviest element formation.

Question 9

The age of a star cluster can be determined by the luminosity of the main sequence turnoff into the giant stage.

Question 10

For binary star systems where the stars are separated by more than 1000 stellar radii,mass transfer is not an issue.

Question 11

When a star becomes a red giant,its core expands to a roughly proportional larger size too.

Question 12

All planetary nebulae are slowly-expanding spherical disks ejected by red giants,while their exposed cores appear as white dwarfs.

Question 13

A star cluster of age 100 million years contains no type O stars.

Question 14

The Sun will get brighter in the next 4 to 5 billion years.

Question 15

Low mass stars should produce white dwarfs,while high mass stars will produce more compact end products.

Question 16

A ten billion year old globular cluster has every star evolved into a giant,with no main sequence stars left.

Question 17

For our Sun,the production of carbon will be the end of its nucleosynthesis.

Question 18

As a star begins to evolve away from the main sequence,it gets larger.

Question 19

While more massive than most of its neighbors,the Sun is still technically a low mass star.

Question 20

When helium fusion begins in a one solar mass main star,it begins gradually,with this rate slowly increasing over time.

Question 21

A star is on the horizontal branch of the H-R diagram.Which statement is true?

A) It is burning both hydrogen and helium.
B) It is about to experience the helium flash.
C) It is burning only helium.
D) The star is contracting.
E) The star is about to return to the main sequence.

Question 22

Refer to the figure above.What is the name of the path between the points labeled 10 and 11?

A) planetary nebula
B) red giant branch
C) horizontal branch
D) asymptotic giant branch
E) white dwarf

Question 23

What are black dwarfs?

A) the lowest mass main sequence stars
B) the end result of massive star evolution
C) objects that are not quite massive enough to be stars
D) pulsars that have slowed down and stopped spinning
E) cooled off white dwarfs that no longer glow visibly

Question 24

During the hydrogen shell burning phase:

A) the star grows more luminous.
B) the star becomes less luminous.
C) helium is burning in the core.
D) the core is expanding.
E) hydrogen is burning in the central core.

Question 25

The "helium flash" occurs at what stage in stellar evolution?

A) when the T Tauri bipolar jets shoot out
B) in the middle of the main sequence stage
C) red giant
D) horizontal branch
E) planetary nebula

Question 26

Refer to the figure above.At what numbered point on the graph above does the helium flash occur?

A) 7
B) 8
C) 9
D) 10
E) 11

Question 27

What spectral type of star that is still around formed longest ago?

A) O
B) A
C) F
D) K
E) M

Question 28

Mass transfer will almost always occur for spectroscopic and eclipsing binaries.

Question 29

What temperature is needed to fuse helium into carbon?

A) 5,800 K
B) 100,000 K
C) 15 million K
D) 100 million K
E) one billion K

Question 30

When a star's inward gravity and outward pressure are balanced,the star is said to be:

A) in gravitational collapse.
B) in thermal expansion.
C) in rotational equilibrium.
D) in hydrostatic equilibrium.
E) a stage 2 protostar.

Question 31

Which of the following elements contained in your body is NOT formed in the cores of stars during thermonuclear fusion?

A) hydrogen
B) carbon
C) calcium
D) iron
E) aluminum

Question 32

A solar mass star will evolve off the main sequence when:

A) it completely runs out of hydrogen.
B) it expels a planetary nebula to cool off and release radiation.
C) it explodes as a violent nova.
D) it builds up a core of inert helium.
E) it loses all its neutrinos, so fusion must cease.

Question 33

A star (no matter what its mass)spends most of its life:

A) as a protostar.
B) as a main sequence star.
C) as a planetary nebula.
D) as a red giant or supergiant.
E) as a T Tauri variable star.

Question 34

What inevitably forces a star like the Sun to evolve away from being a main sequence star?

A) The core begins fusing iron.
B) The star uses up all its supply of hydrogen.
C) The carbon detonation explodes it as a type I supernova.
D) Helium builds up in the core, while the hydrogen burning shell expands.
E) The core loses all its neutrinos, so all fusion ceases.

Question 35

Refer to the figure above.What is the name of the star labeled 10?

A) planetary nebula
B) red giant branch
C) horizontal branch
D) asymptotic giant branch
E) white dwarf

Question 36

Refer to the figure above.What is the name of the path between the points labeled 8 and 9?

A) planetary nebula
B) red giant branch
C) horizontal branch
D) asymptotic giant branch
E) white dwarf

Question 37

At which stage in a Sun-like star's life is its core the least dense?

A) Main Sequence
B) Subgiant Branch
C) Helium Fusion
D) Planetary Nebula
E) White Dwarf

Question 38

Just as a low-mass main sequence star runs out of fuel in its core,it actually becomes brighter.How is this possible?

A) Helium fusion gives more energy than hydrogen fusion does, based on masses.
B) Its outer envelope is stripped away and we see the brilliant core.
C) The core contracts, raising the temperature and increasing the size of the region of hydrogen shell-burning.
D) It explodes.
E) It immediately starts to fuse helium.

Question 39

What spectral type of star that is still around formed most recently?

A) O
B) A
C) F
D) K
E) M

Question 40

What is a planetary nebula?

A) the bipolar jets ejected by a T Tauri variable
B) a planet surrounded by a glowing shell of gas
C) the disk of gas and dust surrounding a young star that will soon form a solar system
D) the ejected envelope, often bipolar, of a red giant surrounding a stellar core remnant
E) a type of young, medium mass star

Question 41

In the evolution of massive stars,what is the significance of the temperature 600 million K?

A) It is the temperature at which helium fuses into carbon.
B) It is the temperature needed for carbon fusing into heavier elements.
C) It is the main sequence core temperature which makes massive stars so bright.
D) It is the temperature needed for helium burning into boron.
E) It is the final temperature reached during their evolution.

Question 42

Which of these will the Sun probably become in the very distant future?

A) hypernova
B) supernova
C) pulsar
D) planetary nebula
E) nova

Question 43

A high-mass star dies more violently than a low-mass star because:

A) it must always end up as a black hole.
B) it generates more heat and its core eventually collapses very suddenly.
C) it cannot fuse elements heavier than carbon.
D) gravity is weakened by its high luminosity.
E) it is most often found as part of a binary system.

Question 44

Which of the following is true regarding planetary nebulae?

A) Some are spherical, but most have bipolar structure.
B) They are the result of the mass loss during the main sequence stage of the most massive stars.
C) They are the rings of material surrounding newly formed stars that will eventually form the planetary systems.
D) They are the ejected envelopes of highly evolved brown dwarf stars.
E) They are the coronas surrounding most blue stragglers.

Question 45

Refer to the figure above.What is the name of the path between the points labeled 13 and 14?

A) planetary nebula
B) red giant branch
C) horizontal branch
D) asymptotic giant branch
E) white dwarf

Question 46

As a 4-10 solar mass star leaves the main sequence on its way to becoming a red supergiant,its luminosity:

A) decreases.
B) first decreases, then increases.
C) increases.
D) remains roughly constant.
E) first increases, then decreases.

Question 47

Which type of star has the strongest stellar winds?

A) giant K- and M-type stars
B) white dwarfs
C) dwarf K- and M-type stars
D) main sequence O- and B-type stars
E) T Tauri stars

Question 48

Virtually all the carbon-rich dust in the plane of the galaxy originated in:

A) low-mass stars.
B) high-mass stars.
C) planetary nebulae.
D) white dwarfs.
E) brown dwarfs.

Question 49

The brightest stars in a young open cluster will be:

A) massive blue stars at the top left on the H-R diagram.
B) red T-tauri stars still heading for the main sequence.
C) red giants that are fusing helium into carbon.
D) yellow giants like our Sun, but much larger.
E) the core stars of planetary nebulae.

Question 50

Which of the following best describes the evolutionary track followed on the H-R diagram for the most massive stars?

A) vertically upward, along the left edge of the diagram
B) diagonally to lower right, then vertical, then horizontally left
C) horizontally right, diagonally to lower left, then horizontally right
D) horizontally right
E) horizontally right, then forms a clockwise loop

Question 51

Which of the following best describes the evolutionary track of the most massive stars?

A) diagonally to lower right, then vertical, then horizontal left
B) horizontally right, diagonal to lower left, then horizontal right
C) horizontal right, then a clockwise loop
D) horizontal right
E) vertically left, then straight down

Question 52

Some globular clusters have three main sequence tracks.This indicates:

A) three different stellar compositions.
B) three episodes of star formation, separated by billions of years.
C) stars evolve through three different mechanisms.
D) the stars were observed from three different telescopes.

Question 53

The brightest stars of a young open cluster will be:

A) Cepheid variables.
B) massive blue main sequence stars.
C) red giants.
D) yellow main sequence stars like the Sun.
E) T Tauri variables.

Question 54

Compared to our Sun,a typical white dwarf has:

A) about the same mass and density.
B) about the same mass and a million times higher density.
C) a larger mass and a 100 times lower density.
D) a smaller mass and half the density.
E) a smaller mass and twice the density.

Question 55

What is the typical age for a globular cluster associated with our Milky Way?

A) a few million years
B) 200 million years
C) a billion years
D) 10-12 billion years
E) 45 billion years

Question 56

The order of evolutionary stages of a star like the Sun would be Main Sequence,giant,planetary nebula,and finally:

A) hypernova.
B) neutron star.
C) white dwarf.
D) nova.
E) black hole.

Question 57

What is the source of the large dust shells seen around some red giants and red supergiants?

A) leftover material from their formation
B) debris left behind by a supernova
C) material from winds from these same stars
D) debris left behind by passing comets
E) star-forming molecular clouds

Question 58

What characteristic of a star cluster is used to determine its age?

A) the ratio of main sequence to white dwarfs stars
B) the number of red giants
C) the faintest stars seen in the cluster
D) the main sequence turnoff
E) the total number of stars in the cluster

Question 59

Refer to the figure above.What is the name of the path between the points labeled 11 and 12?

A) planetary nebula
B) red giant branch
C) horizontal branch
D) asymptotic giant branch
E) white dwarf

Question 60

Isolated main-sequence stars as massive as 10 to 12 times the mass of the Sun may still manage to avoid going supernova.Why?

A) because they can also have strong stellar winds
B) because about half that mass will be contained in the carbon core
C) because they would be classified as brown dwarfs
D) because these stars will eject at least 4 solar masses in the planetary nebula stage
E) because their masses will decrease as they fuse heavy elements into lighter elements in their cores

Question 61

Which stars in globular clusters are believed to be examples of mergers?

A) eclipsing binaries
B) blue supergiants
C) blue stragglers
D) brown dwarfs
E) planetary nebulae cores

Question 62

That brighter Sirius A weighs 3 solar masses,but the white dwarf Sirius B is only about one solar mass implies:

A) that white dwarfs evolve slower than main sequence stars.
B) that the collapsed companion transferred mass to Sirius A.
C) that there should be a planetary nebula around the Sirius system.
D) that Sirius A will be stable three times longer than Sirius B.
E) the Sirius A will end up as a black hole, not a white dwarf like its companion.

Question 63

Noting the turnoff mass in a star cluster allows you to determine its:

A) distance.
B) radial velocity.
C) age.
D) total mass.
E) number of stars.

Question 64

The Main Sequence is the first stellar stage in which energy produced by ________ balances the energy lost by radiation from the surface of the star.

Question 65

Mass transfer in binaries occurs when one giant swells to reach the:

A) Chandrasekhar Limit.
B) Cassini Division.
C) Hayashi Track.
D) Roche Lobe.
E) Herbig-Haro Limit.

Question 66

The thermonuclear process in solar and less massive stars which produces one atom of helium from four of hydrogen is the ________.

Question 67

You observe a low-mass helium white dwarf.What can you conclude?

A) It is over 100 billion years old.
B) It will soon be a planetary nebula.
C) It is part of a binary star system.
D) Its core is mostly carbon.
E) It was once a blue supergiant.

Question 68

The longest stage in the life cycle of a star is as a(n)________ star.

Question 69

The brightest stars in aging globular clusters will be:

A) core stars of planetary nebulae.
B) massive blue main sequence stars like Spica.
C) blue stragglers.
D) red supergiants like Betelguese and Antares.
E) blue supergiants like Rigel and Deneb.

Question 70

Compared to a cluster containing type O and B stars,a cluster with only type F and cooler stars will be:

A) younger.
B) older.
C) further away.
D) more obscured by dust.
E) less obscured by dust.

Question 71

Which is used observationally to determine the age of a star cluster?

A) the total number of main sequence stars
B) the ratio of giants to supergiants
C) the luminosity of the main sequence turn-off point
D) the number of white dwarfs
E) the amount of dust that lies around the cluster

Question 72

In a fairly young star cluster,if the most massive stars are swelling up into giants,the least massive stars are:

A) also evolving off the main sequence as well.
B) continuing to shine as stable main sequence stars.
C) blowing off shells as planetary nebula instead.
D) collapsing directly to white dwarfs.
E) still evolving toward their ZAMS positions.

Question 73

The region in the H-R Diagram where evolved,low mass stars are converting helium to carbon in their cores is the ________.

Question 74

What is a typical age for a globular cluster?

A) 10 million years
B) 200 million years
C) one billion years
D) 4.8 billion years
E) 12 billion years

Question 75

The most famous case of a more massive hot star orbiting with a more evolved but presently less massive red giant is the eclipsing binary:

A) Aldeberan.
B) Antares.
C) Algol.
D) Alberio.
E) Altair.

Question 76

What is the unusual result of mass transfer in the Algol binary system?

A) a helium white dwarf
B) a carbon white dwarf
C) a black dwarf
D) a red dwarf
E) a brown dwarf

Question 77

The Roche lobe of a star in a binary star system:

A) resembles the ear of Edouard Roche, a French mathematician.
B) is, in terms of the star's gravity, its "zone of influence."
C) is the part of a rapidly rotating star that will eventually spin away to form planets.
D) is the accretion disk around the companion star.
E) leads to formation of rings, like around the jovian planets.

Question 78

In globular clusters,the brightest stars will be:

A) massive blue main sequence stars.
B) red supergiants.
C) T Tauri stars.
D) blue stragglers.
E) planetary nebulae.

Question 79

The thermonuclear process in high mass stars that produces one atom of helium from four of hydrogen is the ________.

Question 80

In an H-R Diagram,the path showing changes in a star's luminosity and surface temperature as a function of time is called its ________.