Multiple-Choice Questions
1) A star will spend most of its life
A) as a protostar.
B) on the main sequence.
C) inside its planetary nebula.
D) in repeated swellings to the red giant.
E) in a sustained helium flash lasting billions of years.
Page Ref: 12.1
2) 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.
Page Ref: 12.1
3) What temperature is needed to fuse helium into carbon?
A) 100,000 K
B) 15 million K
C) 100 million K
D) 400 million K
E) 10 billion K
Page Ref: 12.2
4) When a low mass star first runs short of hydrogen in its core, it becomes brighter because
A) it explodes as a nova.
B) helium fusion gives off more energy than does hydrogen.
C) its outer, cooler layers are shed, and we see the brighter central core.
D) the core contracts, raising the temperature and hydrogen burning shell outward.
E) the helium flash increases the size of the star immensely.
Page Ref: 12.2
5) 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.
Page Ref: 12.2
6) The helium flash converts helium nuclei into
A) boron.
B) beryllium.
C) carbon.
D) oxygen.
E) iron.
Page Ref: 12.2
7) 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.
Page Ref: 12.2
8) Can a star become a red giant more than once?
A) yes, before and after the helium flash
B) yes, before and after the Type II supernova event
C) no, the planetary nebula blows off all the outer shells completely
D) no, it will lose so much mass as to cross the Chandrasekhar Limit
E) no, or we would see them as the majority of naked-eye stars
Page Ref: 12.2
9) 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.
Page Ref: 12.2
10) A white dwarf has the mass of the Sun and the volume of
A) Jupiter.
B) Earth.
C) Mars.
D) the Moon.
E) Eros.
Page Ref: 12.3
11) The outward pressure in the core of a red giant balances the inward pull of gravity when
A) the electrons are compressed so much they are all in contact.
B) the electrons and protons have combined to form neutrons.
C) hydrogen begins fusing into helium.
D) carbon fuses into heavier elements.
E) iron forms in the inner core.
Page Ref: 12.3
12) Which of these is true of planetary nebulae?
A) They are expelled by the most massive stars in their final stages before supernova.
B) They are rings of material around protostars that will accrete into planets in time.
C) They are ejected envelopes surrounding a highly evolved low mass star.
D) They are the envelopes that form when blue stragglers merge.
E) They are the material which causes the eclipses in eclipsing binary systems.
Page Ref: 12.3
13) 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 and half the density.
E) a smaller mass and twice the density.
Page Ref: 12.3
14) A ________ represents a relatively peaceful mass loss as a giant core becomes a white dwarf.
A) nova.
B) emission nebula.
C) supernova remnant.
D) planetary nebula.
E) supernova.
Page Ref: 12.3
15) A surface explosion when a companion spills hydrogen onto its close white dwarf companion creates a
A) Type I supernova.
B) Type II supernova.
C) emission nebula.
D) planetary nebula.
E) nova.
Page Ref: 12.3
16) Which of these evolutionary paths is the fate of our Sun?
A) brown dwarf
B) supernova of type II
C) pulsar
D) planetary nebula
E) nova
Page Ref: 12.3
17) When the outer envelope of a red giant recedes, the remaining carbon core is called a
A) black dwarf.
B) white dwarf.
C) planetary nebula.
D) black hole.
E) brown dwarf.
Page Ref: 12.3
18) The initial mass of a protostar generally determines the star's future evolution. But in many cases, what can alter this process?
A) The star may be isolated in space, far from other influences.
B) The star may be in a spectroscopic binary system.
C) The star may gain mass by passing through a dark cloud.
D) The star may collide with another, unrelated star.
E) The star may drift away from the other stars in its formation cluster.
Page Ref: 12.3
19) Black dwarfs are
A) very common, making up the majority of the dark matter in the universe
B) often made from very low mass protostars that never fuse hydrogen
C) rare, for collapsing cores of over three solar masses are uncommon
D) rare, for few binary systems are close enough for this merger to happen
E) not found yet; the oldest, coldest white dwarf in the Galaxy has not cooled enough yet
Page Ref: 12.3
20) Virtually all the carbon-rich dust in the plane of the galaxy originated in
A) low-mass stars.
B) high-mass stars.
C) Type II supernovae.
D) Type I supernovae.
E) the carbon cores of Type O stars.
Page Ref: 12.3
21) 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 Type II supernova.
C) It is part of a binary star system.
D) Its core is mostly carbon.
E) It was once a blue supergiant.
Page Ref: 12.3
22) Of the elements in your body, the only one not formed in stars is
A) hydrogen.
B) carbon.
C) calcium.
D) iron.
E) aluminum.
Page Ref: 12.4
23) An iron core cannot support a giant star because
A) iron is heavy, and settles to the earth's core.
B) iron has a poor binding energy, and decays rapidly into lead.
C) iron cannot fuse with other elements and produce additional energy in fusion.
D) iron cannot fuse with any other elements at all.
E) iron is too dense, and produces too much gravity.
Page Ref: 12.4
24) A 20 solar mass star will stay on the main sequence for 10 million years, yet its iron core can exist for only a
A) day.
B) week.
C) month.
D) year.
E) century.
Page Ref: 12.4
25) As a star's evolution approaches the Type II supernova, we find
A) the heavier the element, the less time it takes to make it.
B) the heavier the element, the higher the temperature to fuse it.
C) helium to carbon fusion takes at least 100 million K to start.
D) photodisintegration of iron nuclei begins at 10 billion K to ignite the supernova.
E) All of the above are correct.
Page Ref: 12.4
26) 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.
Page Ref: 12.4
27) 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
Page Ref: 12.4
28) Type II supernovae occur when their cores start making
A) carbon.
B) oxygen.
C) silicon.
D) iron.
E) uranium.
Page Ref: 12.5
29) If it gains sufficient mass, a white dwarf can become a
A) brown dwarf.
B) type II supernova.
C) type I supernova.
D) planetary nebula.
E) black dwarf.
Page Ref: 12.5
30) For a white dwarf to explode entirely as a Type I supernova, it's mass must be
A) at least 0.08 solar masses.
B) 1.4 solar masses, the Chandrasekhar Limit.
C) 3 solar masses, the Schwartzschild Limit.
D) 20 solar masses, the Hubble Limit.
E) 100 solar masses, the most massive known stars.
Page Ref: 12.5
31) The heaviest nuclei of all are formed
A) in the horizontal branch.
B) in dense white dwarfs.
C) during nova explosions.
D) in the ejection of matter in the planetary nebula.
E) in the core collapse that set the stage of Type II supernovae.
Page Ref: 12.5
32) The Chandrasekhar Limit is
A) the upper mass limit for a white dwarf.
B) the temperature at which hydrogen fusion starts.
C) the temperature at which helium fusion starts.
D) the point at which a planetary nebula forms.
E) the lower mass limit for a Type II supernova.
Page Ref: 12.5
33) Where was supernova 1987A located?
A) in the Orion Nebula, M-42
B) in M-13, one of the closest of the evolved globular clusters
C) in the sagitarius arm of the Milky Way, about 12,000 ly distant
D) in our companion galaxy, the Large Magellanic Cloud
E) near the core of the Andromeda Galaxy, M-31
Page Ref: 12.5
34) Which of these events is not possible?
A) low-mass stars swelling up to produce planetary nebulae
B) red giants exploding as Type II supernovae
C) close binary stars producing recurrent novae explosions
D) white dwarfs and companion stars producing recurrent Type I supernova events
E) a white dwarf being found in the center of a planetary nebula
Page Ref: 12.5
35) Which of these does not depend on a close binary system to occur?
A) a nova
B) a Type I supernova
C) a Type II supernova
D) All of these need mass transfer to occur.
E) None of these depend on mass transfer.
Page Ref: 12.5
36) What can you conclude about a Type I supernova?
A) It was originally a low-mass star.
B) It was originally a high mass star.
C) Its spectrum will show large amounts of hydrogen.
D) Its core was mostly iron.
E) The star never reached the Chandrasekhar Limit.
Page Ref: 12.5
37) A recurrent nova could eventually build up to a
A) planetary nebula.
B) Type I supernova.
C) Type II supernova.
D) hypernova.
E) quasar.
Page Ref: 12.5
38) 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.
Page Ref: 12.6
39) 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
Page Ref: 12.6
40) 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
Page Ref: 12.6
41) 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.
Page Ref: 12.6
42) 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.
Page Ref: 12.6
43) 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.
Page Ref: 12.6
44) 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.
Page Ref: 12.6
45) 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
Page Ref: 12.6
46) What was most surprising about SN 1987 A?
A) The parent star was a blue supergiant, much like Deneb or Rigel.
B) The supernova was luminous enough to see with the naked eye.
C) The supernova was not even in our own Galaxy.
D) It did not produce the flood of neutrinos our models had led us to expect.
E) Its pulsar appeared within weeks of the explosion.
Page Ref: 12.7
47) What made supernova 1987A so useful?
A) Its parent star had been studied previously.
B) As it was in the Large Magellanic Cloud, we knew it was 170,000 ly distant.
C) It was spotted while still on the rise, and its light curve is well established.
D) The Hubble Space Telescope was available for high resolution images.
E) All of the above are true.
Page Ref: 12.7