A white dwarf is ________.
  • a set of steps by which four hydrogen nuclei fuse into one helium nucleus
  • Most stars in the cluster are yellow or reddish in color.
  • what most stars become when they die
  • radius and surface temperature.
Two stars have the same spectral type. Star X is in luminosity class III, while Star Y is in luminosity class V.Star X must be larger in radius than Star Y.
  • M stars
  • visual binary
  • True
  • False
Light escaping from white dwarfs will show a gravitational redshift.
  • False
  • M stars
  • True
  • iron
Stars with high masses live longer than stars with lower masses.
  • 0.01 solar
  • False
  • O and B stars
  • True
Observations show that elements with atomic mass numbers divisible by 4 (such as oxygen-16, neon-20, andmagnesium-24) tend to be more abundant in the universe than elements with atomic mass numbers inbetween. Why do we think this is the case?
  • Near the end of a high-mass star's life, it produces new elements through a series of helium capturereactions.
  • The diagram shows main-sequence stars of every spectral type except O, along with a few giants andsupergiants.
  • At these high temperatures, nearly all the hydrogen is ionized, and is therefore unable to interact withlight.
  • A few massive stars will form, live, and die before the majority of the star's clusters even complete theirprotostar stage.
What can we learn about a star from its life track on an H-R diagram?
  • They generate energy through hydrogen fusion in their core.
  • Higher core temperatures cause fusion to proceed much more rapidly.
  • what surface temperature and luminosity it will have at each stage of its life
  • It is the center of the black hole, a place of infinite density where the known laws of physics cannotdescribe the conditions.
The sketch above shows groups of stars on the H-R diagram, labeled (a) through (e); note that (a) representsthe entire main sequence while (c) and (d) represent only small parts of the main sequence. Which grouprepresents the most common type of stars?
  • The diagram shows main-sequence stars of every spectral type except O, along with a few giants andsupergiants.
  • d
  • The entire mass of the Earth would end up as a thin layer, about 1 cm thick, over the surface of theneutron star.
  • d .
What is the approximate surface temperature of a B star?
  • Three quarters hydrogen, one quarter helium, no more than 2% heavier elements
  • 20,000 K
  • 0.01 solar
  • They generate energy through hydrogen fusion in their core.
Based on current evidence, which of the following statements about gamma-ray bursts is true?
  • stars that are more massive than eight times the mass of the Sun
  • All of the above are true.
  • All the bursts that we have detected occurred in distant galaxies.
  • 3 solar masses
A star of spectral type G will last approximately how long on the main sequence?
  • 10 million years
  • 10 million K
  • 10 billion years
  • a 1 solar mass star
In any star cluster, stars with lower masses greatly outnumber those with higher masses.
  • False
  • iron
  • True
  • upper right
Why does a star grow larger immediately after it exhausts its core hydrogen?
  • At these high temperatures, nearly all the hydrogen is ionized, and is therefore unable to interact withlight.
  • when the rate of hydrogen fusion in the star's core is high enough to sustain gravitational equilibrium
  • Hydrogen fusion in a shell outside the core generates enough thermal pressure to push the upperlayers outward.
  • The diagram shows main-sequence stars of every spectral type except O, along with a few giants andsupergiants.
What is the approximate luminosity of a main-sequence M star?
  • a 1 solar mass star
  • O and B stars
  • 0.01 solar
  • 0.1 solar radius
What is a planetary nebula?
  • gas ejected from a star in the final stage of its life
  • a white dwarf star with a red giant binary companion
  • They generate energy through hydrogen fusion in their core.
  • a type of hydrogen fusion that uses carbon, nitrogen, and oxygen atoms as catalysts
What kind of star is most likely to become a white-dwarf supernova?
  • below and to the right of the lowest part of the main sequence
  • what surface temperature and luminosity it will have at each stage of its life
  • They generate energy through hydrogen fusion in their core.
  • a white dwarf star with a red giant binary companion
What do we mean by the main-sequence turnoff point of a star cluster, and what does it tell us?
  • The diagram shows main-sequence stars of every spectral type except O, along with a few giants andsupergiants.
  • when the rate of hydrogen fusion in the star's core is high enough to sustain gravitational equilibrium
  • It is the spectral type of the hottest main-sequence star in a star cluster, and it tells us the cluster's age
  • both stars have the same luminosity, but the apparent brightness of Star B is four times that of Star A
Which stellar spectral type has strong molecular absorption lines in its optical spectrum?
  • d
  • Higher core temperatures cause fusion to proceed much more rapidly.
  • All of the above are true.
  • B
Careful measurements reveal that a star maintains a steady apparent brightness at most times, except that atprecise intervals of 73 hours the star becomes dimmer for about 2 hours. The change in brightness alternatesbetween a small change and a large change. The most likely explanation is that ________.
  • Three quarters hydrogen, one quarter helium, no more than 2% heavier elements
  • the rate at which it converts hydrogen to helium.
  • the star is a member of an eclipsing binary star system
  • The diagram shows main-sequence stars of spectral types G, K, and M, along with numerous giantsand white dwarfs.
Which statement about accretion disks is not true?
  • Degeneracy pressure varies with the temperature of the star.
  • The core quickly heats up and expands as helium fusion begins all at once throughout the core.
  • when the rate of hydrogen fusion in the star's core is high enough to sustain gravitational equilibrium
  • The primary factor determining whether a white dwarf has an accretion disk is the white dwarf's mass.
What happens after the helium flash in the core of a star?
  • The core quickly heats up and expands as helium fusion begins all at once throughout the core.
  • when the rate of hydrogen fusion in the star's core is high enough to sustain gravitational equilibrium
  • Hydrogen fusion in a shell outside the core generates enough thermal pressure to push the upperlayers outward.
  • what surface temperature and luminosity it will have at each stage of its life
Which of the following statements about degeneracy pressure is not true?
  • Degeneracy pressure varies with the temperature of the star.
  • luminosity
  • H-R diagrams of globular clusters
  • Brown dwarfs eventually collapse to become white dwarfs.
If you were to come back to our solar system in 6 billion years, what might you expect to find?
  • a white dwarf
  • O and B stars
  • 10 billion years
  • as much as a large vehicle
On the main sequence, stars obtain their energy
  • a 1 solar mass star
  • .More massive stars live much shorter lives than less massive stars.
  • by converting hydrogen to helium.
  • can be determined for main-sequence stars but not for other types of stars
Two stars both lie on the main sequence. Star X is spectral type A, while Star Y is spectral type G. Star X mustbe more massive than Star Y.
  • False
  • True
  • iron
  • their radii
The total amount of power (in watts, for example) that a star radiates into space is called its ________.
  • their radii
  • lower right
  • luminosity
  • lower left
What types of stars end their lives with supernovae?
  • Most stars in the cluster are yellow or reddish in color.
  • when the rate of hydrogen fusion in the star's core is high enough to sustain gravitational equilibrium
  • what surface temperature and luminosity it will have at each stage of its life
  • stars that are more massive than eight times the mass of the Sun
Which of the following best describes what would happen if a 1.5 solar mass neutron star, with a diameter ofa few kilometers, were suddenly to appear in your hometown?
  • The entire mass of the Earth would end up as a thin layer, about 1 cm thick, over the surface of theneutron star.
  • The primary factor determining whether a white dwarf has an accretion disk is the white dwarf's mass.
  • Temperatures skyrocket to the point where carbon fusion is possible, which leads to a white dwarfsupernova explosion.
  • apparent brightness = luminosity/ 4pi x (distance)^2
On a Hertzsprung-Russell diagram, where would you find stars that are cool and have low luminosities?
  • lower right
  • 10 million K
  • lower left
  • a 1 solar mass star
You observe a red giant star. What is happening to that star?
  • Hydrogen fusion in a shell outside the core generates enough thermal pressure to push the upperlayers outward.
  • Three quarters hydrogen, one quarter helium, no more than 2% heavier elements
  • It is increasing in size, and is fusing hydrogen in a shell around its core.
  • They generate energy through hydrogen fusion in their core.
Which star spends the longest time in the protostellar phase of life?
  • luminosity
  • as much as a large vehicle
  • 10 million years
  • a 1 solar mass star
Will our Sun ever undergo a white dwarf supernova explosion? Why or why not?
  • No, because it is not orbited by another star.
  • It is significantly less massive than the Sun.
  • It would evolve more quickly than it is now.
  • a 1 solar mass star
How is the lifetime of a star related to its mass?
  • .More massive stars live much shorter lives than less massive stars.
  • Degeneracy pressure varies with the temperature of the star.
  • an explosion on the surface of a white dwarf in a close binary system
  • a type of hydrogen fusion that uses carbon, nitrogen, and oxygen atoms as catalysts
Which of the following statements about brown dwarfs is not true?
  • Brown dwarfs eventually collapse to become white dwarfs.
  • Degeneracy pressure varies with the temperature of the star.
  • apparent brightness = luminosity/ 4pi x (distance)^2
  • All of the above are true.
Consider the star to which the arrow points. Which of the following statements about this star is not true?
  • It is increasing in size, and is fusing hydrogen in a shell around its core.
  • A few massive stars will form, live, and die before the majority of the star's clusters even complete theirprotostar stage.
  • apparent brightness = luminosity/ 4pi x (distance)^2
  • It is significantly less massive than the Sun.
Which of the following terms is given to a pair of stars that appear to change position in the sky, indicatingthat they are orbiting one another?
  • O and B stars
  • apparent brightness = luminosity/ 4pi x (distance)^2
  • H-R diagrams of globular clusters
  • visual binary
it is a graph with a blocked question:-)
  • A) About 1 solar
  • gas ejected from a star in the final stage of its life
  • O and B stars
  • as much as a large vehicle
The helium fusion process works by fusing two helium nuclei into one beryllium nucleus.
  • True
  • M stars
  • False
  • iron
Suppose you were unfortunate enough to fall into a black hole in a binary system where the black hole wasaccreting matter from its companion star. Which of the following is most likely to kill you first?
  • apparent brightness = luminosity/ 4pi x (distance)^2
  • X-rays from the accretion disk
  • H-R diagrams of globular clusters
  • by converting hydrogen to helium.
Based on current understanding, the minimum mass of a black hole that forms during a massive starsupernova is roughly ________.
  • 3 solar masses
  • luminosity
  • lower right
  • 0.1 solar radius
Which of the statements below about black holes is not true?
  • O and B stars
  • A spaceship passing a few million kilometers from a 10 solar mass black hole is much more likely to bedestroyed than a spaceship passing at the same distance from the center of a 10 solar massmain-sequence star
  • It is the center of the black hole, a place of infinite density where the known laws of physics cannotdescribe the conditions.
  • Degeneracy pressure varies with the temperature of the star.
Consider a large molecular cloud that will give birth to a cluster of stars. Which of the following would youexpect to be true?
  • The diagram shows main-sequence stars of every spectral type except O, along with a few giants andsupergiants.
  • .More massive stars live much shorter lives than less massive stars.
  • A few massive stars will form, live, and die before the majority of the star's clusters even complete theirprotostar stage.
  • Temperatures skyrocket to the point where carbon fusion is possible, which leads to a white dwarfsupernova explosion.
When does a star become a main-sequence star?
  • can be determined for main-sequence stars but not for other types of stars
  • At these high temperatures, nearly all the hydrogen is ionized, and is therefore unable to interact withlight.
  • when the rate of hydrogen fusion in the star's core is high enough to sustain gravitational equilibrium
  • Higher core temperatures cause fusion to proceed much more rapidly.
The choices below each describe the appearance of an H-R diagram for a different star cluster. Which clusteris most likely to be located in the halo of our galaxy?
  • It is the spectral type of the hottest main-sequence star in a star cluster, and it tells us the cluster's age
  • The diagram shows main-sequence stars of spectral types G, K, and M, along with numerous giantsand white dwarfs.
  • The entire mass of the Earth would end up as a thin layer, about 1 cm thick, over the surface of theneutron star.
  • H-R diagrams of globular clusters
Photographs of many young stars show long jets of material apparently being ejected from their poles.
  • Three quarters hydrogen, one quarter helium, no more than 2% heavier elements
  • True
  • False
  • M stars
Which of the following statements about apparent and absolute magnitudes is true?
  • apparent brightness = luminosity/ 4pi x (distance)^2
  • Brown dwarfs eventually collapse to become white dwarfs.
  • All of the above are true.
  • Most stars in the cluster are yellow or reddish in color.
Which of the following types of stars is the most common?
  • M stars
  • All of the above are true.
  • 0.01 solar
  • 20,000 K
Our Sun will end its life in a planetary nebula and become a white dwarf.
  • False
  • True
  • upper right
  • M stars
A star of spectral type B with a mass of 10 times the mass of the Sun will last approximately how long on themain sequence?
  • a white dwarf
  • 3 solar masses
  • 10 million years
  • 10 million K
The maximum mass for a white dwarf is 1.4 solar masses.
  • 0.01 solar
  • False
  • iron
  • True
How are elements beyond iron formed in massive-star supernovae?
  • below and to the right of the lowest part of the main sequence
  • Neutrons produced during the core collapse are slammed into atomic nuclei.
  • Brown dwarfs eventually collapse to become white dwarfs.
  • what surface temperature and luminosity it will have at each stage of its life
What do we mean by the singularity of a black hole?
  • It is the center of the black hole, a place of infinite density where the known laws of physics cannotdescribe the conditions.
  • when the rate of hydrogen fusion in the star's core is high enough to sustain gravitational equilibrium
  • below and to the right of the lowest part of the main sequence
  • Hydrogen fusion in a shell outside the core generates enough thermal pressure to push the upperlayers outward.
On an H-R diagram, stellar masses ________.
  • .More massive stars live much shorter lives than less massive stars.
  • what surface temperature and luminosity it will have at each stage of its life
  • when the rate of hydrogen fusion in the star's core is high enough to sustain gravitational equilibrium
  • can be determined for main-sequence stars but not for other types of stars
Our Sun will likely undergo a nova event in about 5 billion years.
  • False
  • True
  • a white dwarf
  • O and B stars
When we see X-rays from an accretion disk in a binary system, we can't immediately tell whether theaccretion disk surrounds a neutron star or a black hole. Suppose we then observe each of the followingphenomena in this system. Which one would rule out the possibility of a black hole?
  • All of the above are true.
  • a white dwarf
  • intense X-ray bursts
  • H-R diagrams of globular clusters
What is the approximate chemical composition (by mass) with which all stars are born?
  • They generate energy through hydrogen fusion in their core.
  • It is increasing in size, and is fusing hydrogen in a shell around its core.
  • Most stars in the cluster are yellow or reddish in color.
  • Three quarters hydrogen, one quarter helium, no more than 2% heavier elements
Why do O stars exhibit weak hydrogen absorption lines?
  • At these high temperatures, nearly all the hydrogen is ionized, and is therefore unable to interact withlight.
  • Most stars in the cluster are yellow or reddish in color.
  • It is the center of the black hole, a place of infinite density where the known laws of physics cannotdescribe the conditions.
  • A spaceship passing a few million kilometers from a 10 solar mass black hole is much more likely to bedestroyed than a spaceship passing at the same distance from the center of a 10 solar massmain-sequence star
This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with romannumerals. Which stage lasts the longest?
  • iii
  • True
  • luminosity
  • their radii
What is the common trait of all main-sequence stars?
  • stars that are more massive than eight times the mass of the Sun
  • Degeneracy pressure varies with the temperature of the star.
  • They generate energy through hydrogen fusion in their core.
  • .More massive stars live much shorter lives than less massive stars.
Which of the following stellar properties has the greatest range in values?
  • All of the above are true.
  • H-R diagrams of globular clusters
  • Most stars in the cluster are yellow or reddish in color.
  • luminosity
A star's luminosity depends primarily on its
  • All of the above are true.
  • H-R diagrams of globular clusters
  • radius and surface temperature.
  • 0.1 solar radius
All massive-star supernovae leave behind black holes as remnants.
  • True
  • It is increasing in size, and is fusing hydrogen in a shell around its core.
  • False
  • M stars
On a Hertzsprung-Russell diagram, where would you find white dwarfs?
  • 10 billion years
  • False
  • lower left
  • True
A 10 solar mass star is about ten times more luminous than a 1 solar mass star.
  • False
  • 0.01 solar
  • luminosity
  • True
After a massive-star supernova, what is left behind?
  • Higher core temperatures cause fusion to proceed much more rapidly.
  • what most stars become when they die
  • either a neutron star or a black hole
  • the rate at which it converts hydrogen to helium.
Which element has the lowest mass per nuclear particle and therefore cannot release energy by either fusionor fission?
  • True
  • False
  • iron
  • luminosity
If you had something the size of a sugar cube that was made of white dwarf matter, on Earth it would weigh________.
  • a white dwarf
  • as much as a large vehicle
  • All of the above are true.
  • It would evolve more quickly than it is now.
The sketch above shows groups of stars on the H-R diagram, labeled (a) through (e); note that (a) representsthe entire main sequence while (c) and (d) represent only small parts of the main sequence. Which grouprepresents stars that have no ongoing nuclear fusion?
  • A
  • d .
  • intense X-ray bursts
  • b
We can measure the parallax of most stars in our galaxy.
  • lower left
  • True
  • stars that are more massive than eight times the mass of the Sun
  • False
The more distant a star, the smaller its parallax.
  • M stars
  • True
  • False
  • when the rate of hydrogen fusion in the star's core is high enough to sustain gravitational equilibrium
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