Deck 23: The Death of Stars

Question 1

Astronomers observe a young cluster of stars, where stars with three times the mass of the Sun are still on the main sequence of the H-R diagram. Yet the cluster contains two white dwarfs, each with a mass less than 1.4 times the mass of the Sun. If we can show that the white dwarfs are definitely part of the cluster, how can their presence so soon in the life of the cluster be explained?

A) the lower the mass of a star, the more quickly it goes through each stage of its life
B) white dwarfs are what is left over after a star explodes and throws off 90% of its mass
C) some stars can lose a lot of mass on their way to becoming white dwarfs; thus the white dwarfs could have started out as quite massive stars
D) stars less massive than 1.4 times the mass of the Sun go through the white dwarf stage in their lives before they become main sequence stars
E) astronomers can think of no way to explain this problem; it has them completely baffled

Answer 1

some stars can lose a lot of mass on their way to becoming white dwarfs; thus the white dwarfs could have started out as quite massive stars

Question 2

Which of the following is the smallest?

A) white dwarf
B) neutron star
C) red giant
D) main sequence star
E) protostar

Answer 2

neutron star

Question 3

In a collapsing star of high mass, when electrons and protons are squeezed together with enormous force, they turn into a neutron and a:

A) positron
B) helium nucleus
C) neutrino
D) radio wave
E) nucleus of iron

Answer 3

neutrino

Question 4

A star with a mass like the Sun which will soon die is observed to be surrounded by a large amount of dust and gas -- all material it has expelled in the late stages of its life. If astronomers want to observe the radiation from such a giant star surrounded by its own debris, which of the following bands of the spectrum would be the best to use to observe it?

A) gamma-rays
B) x-rays
C) ultraviolet
D) infrared
E) very long wavelength radio waves

Question 5

Astronomers have long realized that supernovae -- when they explode -- give off an enormous amount of light. But observations of Supernova 1987A (in the Large Magellanic Cloud) revealed that the supernova gives off even more energy in another form? That form is:

A) radio waves
B) WIMPS
C) dark matter
D) sound
E) neutrinos

Question 6

A charming friend of yours who has been reading a little bit about astronomy accompanies you to the campus observatory and asks to see the kind of star that our Sun will ultimately become, long, long after it has turned into a white dwarf. Why is the astronomer on duty going to have a bit of a problem satisfying her request?

A) after being a white dwarf, the Sun will explode, and there will be nothing left to see
B) the universe is not even old enough to have produced any white dwarfs yet
C) all the old stars in our Galaxy are located in globular clusters and all of these are too far away to be seen with the kind of telescope a college or university campus would have
D) after a white dwarf cools off it becomes too cold and dark to emit visible light
E) astronomers only let people with PhD's look at these stellar corpses; it's like an initiation rite for those who become astronomers

Question 7

Which of the following statements about the life of a star with a mass like the Sun is correct?

A) before the star dies, it will fuse dozens of elements in its core
B) as the star is dying, a considerable part of its mass will be lost into space
C) after the main sequence stage, there is no further fusion of hydrogen anywhere in the star
D) at the end of its life, the star will explode as a supernova
E) the core of this star will be too massive to form a white dwarf

Question 8

When a single star with a mass equal to the Sun dies, it will become a

A) white dwarf
B) neutron star
C) black hole
D) pulsar
E) burster

Question 9

Which of the following is the largest (in diameter)?

A) neutron star
B) white dwarf
C) red giant
D) main sequence star
E) the cloud of fossil-fuel pollution around Bayonne, New Jersey

Question 10

Which of the following stages will the Sun definitely go through as it gets older?

A) red giant
B) source of a planetary nebula
C) white dwarf
D) black dwarf
E) all the above

Question 11

A neutron star is as dense as

A) water
B) the center of the Earth
C) a white dwarf star
D) the nucleus of an atom
E) our astronomy textbook

Question 12

Because white dwarfs are small, as their name implies, they are hard to see. What is a way astronomers have to find white dwarfs that distinguishes them from main sequence stars?

A) because white dwarfs get really hot, we can search for their ultraviolet radiation
B) because white dwarfs all have planets around them, we can use the transit method to find them
C) because white dwarfs are making complex molecules in their outer regions, we can search for them with radio telescopes
D) all white dwarfs pulsate (they get brighter and dimmer) every few minutes and this regular change in brightness is easy to notice
E) there is no way to distinguish white dwarfs from other dim stars. That's why we only know two or three white dwarfs in the sky.
Section 23.2: The Evolution of Massive Stars: An Explosive Finish

Question 13

When the mass of a star's core is greater than 1.4 times the mass of the Sun, degenerate electrons can't keep it stable as a white dwarf. Instead, it becomes:

A) a neutron star
B) a planetary nebula
C) a red giant
D) a ball of solid iron, with layers of other elements around it
E) a black dwarf

Question 14

Which of the following stages can only occur in the life of a low-mass star (whose final mass is less than 1.4 times the mass of the Sun)?

A) proto-star
B) main-sequence
C) red giant
D) white dwarf
E) supernova

Question 15

Which of the following is a characteristic of degenerate matter in a white dwarf star?

A) helium is actively fusing into carbon
B) electrons and protons join together in the nucleus to make neutrons and neutrinos
C) the degenerate matter region is expanding as time passes, until it covers a region the size of the orbit of Mars
D) the electrons get as close to each other as possible and resist further compression
E) the atoms drink, smoke, use bad language, and are attracted to the wrong kinds of particles

Question 16

If observations of supernovae in other galaxies show that such an explosion happens in a spiral galaxy like the Milky Way on average every 25 to 100 years, why have astronomers on Earth not seen a supernova explosion in our Galaxy since 1604?

A) we have been very unlucky; there have been far fewer explosions than average recently
B) all the explosions happened in that part of the sky which is only visible from the Earth's southern hemisphere, and we do not have any large telescopes down there
C) the disk of our Galaxy contains a great deal of dust, which tends to block the light of supernova explosions from more distant parts of our Galaxy
D) most supernova explosions produce only high-energy gamma-rays and very little light
E) actually, there have been supernova explosions observed, but there is a government conspiracy to keep ordinary citizens from learning about them (just like the alien creatures that were in Roswell, New Mexico and Area 51)

Question 17

What incident in a massive star's life sets off (begins) the very quick chain of events that leads to a supernova explosion?

A) swelling up to become a red giant
B) the fusion of iron
C) helium begins to fuse into carbon
D) an event horizon forms
E) the star's core becomes degenerate and the electrons don't allow further compression

Question 18

After the core of a massive star becomes a neutron star, the rest of the star's material

A) falls inward very slowly, taking billions of years to get really compressed
B) makes a planetary nebula, which gently moves outward from the center
C) is vaporized by the incredible heat of the dying star and evaporates
D) explodes outward as a supernova
E) continues regular fusion and returns to the main sequence

Question 19

The most stable (tightly bound) atomic nucleus in the universe is:

A) hydrogen
B) carbon
C) uranium
D) technetium
E) iron

Question 20

A white dwarf, compared to a main sequence star with the same mass, would always be:

A) redder in color
B) smaller in diameter
C) the same size
D) younger in age
E) more massive

Question 21

Although centuries ago, astronomers thought that a nova was a new star, appearing for the first time in the heavens, today we know that it is:

A) a binary star system in which one star is a white dwarf and mass is being transferred to it
B) the explosion of a massive star when the fusion of iron leads to the collapse of its core
C) the brightening of a neutron star when it becomes a pulsar
D) the emission of a bright planetary nebula late in a star's life
E) the birth of a high-mass protostar in a giant molecular cloud

Question 22

What kind of telescope did Jocelyn Bell use to discover pul?sars in 1968?

A) visible light
B) radio
C) ultraviolet
D) x-ray
E) neutr?ino

Question 23

Elements heavier than iron can be created during:

A) the big bang
B) the main sequence
C) a supernova explosion
D) the red giant stage in a star's life
E) astronomers don't have any idea of where these elements came from; it's an unsolved mystery
Section 23.3: Supernova Observations

Question 24

Which of the following is NOT a result of supernova explosions?

A) many of the elements the star fused during its life are blasted out into space
B) new heavier elements (including such heavy nuclei lead and uranium) are fused by neutron bombardment during the explosion
C) a tremendous flood of high-energy cosmic ray particles is released
D) any planets within a few dozen LY of the explosion are bathed with life-threatening radiation
E) the neutron star is disrupted and tears apart into many pieces

Question 25

Where does the energy come from that allows the Crab Nebula to keep shining almost a 1000 years after the star exploded? (Who ultimately "pays the energy bill"?)

A) material is still being ejected from the star in the form of a planetary nebula
B) a massive black hole is "eating" material at the center of the nebula
C) a neutron star is slowing down (losing rotation energy)
D) large parts of the nebula are falling inward, releasing gravi?tational energy
E) the Crab nebula is a signal station, where some aliens (LGM) are broad?casting beats for rap music

Question 26

Astronomers believe that the many supernova explosions that happened in the Milky Way Galaxy could have played a role in the evolution of life over billions of years. How would they have influenced the development of life on Earth?

A) supernova explosions would have ripped continents from the crust, and caused plate tectonics
B) supernova explosions probably killed off many animal species on Earth with their dangerous radiation, leaving the planet for humans to dominate
C) the cosmic rays produced by supernova explosions would have contributed to the rate of mutations over many generations
D) supernova explosions would have destroyed most of the planets in the Galaxy, tearing them apart, leaving the only the Earth to give rise to life
E) actually, astronomers know that supernova explosions can only affect the star system in which they happen; they have no effect on the rest of the Galaxy

Question 27

A member of the college football team wants to weigh as much as possible. Assuming he could somehow survive on all of them, at the surface of which object would he weigh the most?

A) an O-type star in the main sequence stage of its life
B) an M-type star in the main sequence stage of its life
C) a white dwarf
D) a neutron star
E) you can't fool me, his weight would be the same on all of the above objects
Section 23.5: The Evolution of Binary Star Systems

Question 28

Which of the following statements about the Crab Nebula is FALSE?

A) it is the remnant of a supernova explosion first seen on Earth in 1054 AD
B) the nebula still puts out more energy (at all wavelengths) than 100,000 Suns
C) inside, there are a number of newly formed massive stars (O and B type stars)
D) the neutron star inside shows clear evidence of slowing down just a little bit in its rotation
E) we can detect a pulsar inside the nebula using both radio waves and visible light

Question 29

In a supernova like SN1987A, once the crisis of iron fusion has begun, roughly how long does it take the star's core to collapse?

A) 10 million years
B) 10 thousand years
C) a hundred years
D) one year
E) a few tenths of a second

Question 30

Which of the following is one reason we do not detect a pulsar in many remnants of supernova explosions?

A) most stars (our own Sun, for example) don't rotate at all, so no pulsar can form
B) the radiation with which we detect pulsars doesn't get through the Earth's atmosphere
C) the pulsar beam doesn't happen to point toward us in many cases
D) many supernova remnants contain white dwarfs or black dwarfs
E) the little green men inside put shades on their pulsars for privacy

Question 31

In the model that astronomers have developed for pulsars, why do they suggest that there must be two beams of energy coming from the pulsar?

A) because neutron stars are always surrounded by two moons (satellite bodies)
B) because neutron star beams come out of the north and south poles of a magnetic field
C) because pulsars always come in pairs
D) because pulsars represent supernova explosions that come out in opposite directions (but not every direction) when a massive star dies
E) this is an unsolved mystery in astronomy; no one has any good suggestions

Question 32

When neutron stars were first predicted theoretically, no scientist expected to be able to detect one of them across interstellar distances. What enabled astronomers to find neutron stars in the late 1960's?

A) they give off a lot more light than expected, and can be seen glowing with a reddish light from far away
B) they are so large, their dark outline block a significant amount of starlight from behind them
C) we found strongly magnetic neutron stars whose whirling beams of energy were detected as pulsars
D) some neutron stars soon collapse to be white dwarfs, whose light can be detected further away
E) astronomers have actually only found one neutron star and that was discovered very close to us and by sheer luck

Question 33

How did Supernova 1987A demonstrate that new elements are made in supernova explosions?

A) spectra of the supernova light revealed elements that have never been found in Earth or the stars
B) the neutrinos observed from the supernova could only be produced through radioactive decay of heavy elements
C) a tank with 8000 tons of pure water under Lake Erie detected gamma rays from new elements
D) a pulsar with new elements in it was found using radio telescopes in England
E) the light output was kept at high levels by the energy released from radioactive elements that decay very quickly; these must have been made by the supernova

Question 34

Astronomer have concluded that pulsars are

A) rotating black holes
B) rotating neutron stars
C) rotating red giants
D) supernovae that are about to ex?plode
E) protostars that are collapsing and spinning very rapidly

Question 35

Which of the following statements about Supernova 1987A is FALSE?

A) it exploded relatively close to us, in a spiral arm of the Milky Way Galaxy
B) it was only visible from the Southern Hemisphere of the Earth
C) astronomers believe it was the explosion of a star that was originally a massive type O
D) neutrinos from the explosion were actually detected on Earth
E) it was observed with instruments in space as well as on the ground

Question 36

Some of the energy produced in the event we call Supernova 1987A was used to blow the star apart. Out of the following places that the energy of this event could go, which absorbed by far the most energy?

A) the production of huge numbers of neutrinos
B) the movement of the outer layers of the star in an outward direction
C) the production of visible light (which could be seen with the naked eye from Earth)
D) the production of gamma rays
E) all of the above took roughly the same amount of energy - the energy was pretty evenly divided among them
Section 23.4: Pulsars and the Discovery of Neutron Stars

Question 37

Astronomers have noticed that the visible filaments in the Crab Nebula are moving toward us at great speed. How can they know about motions like this?

A) from the width of the pulsar pulses
B) from the color of the nebula's continuous radiation
C) from the spacing of the pulsar pulses
D) from the H-R diagram
E) from the Doppler shift in the line radiation from the nebula

Question 38

When a star undergoes a nova explosion, it may return to its "quiet state" and later become a nova again. What would allow a nova explosion to happen to a star more than once?

A) the star that goes nova collides with several stars in a star cluster
B) the star that goes nova has a companion star near it, which dumps material onto the first star and continues to do so even after the first nova explosion
C) the star that goes nova has a number of massive planets around it which fall in
D) the star that goes nova has an iron catastrophe in its core and then another step in the fusion of heavy elements producer another explosion
E) a nova explosion happens each time a neutron star rotates to face us, and that happens every century or so

Question 39

Which of the following statements about a Type II Supernova is true?

A) Type II supernovas happen when a white dwarf is overloaded with mass from a companion star
B) Type II supernovas occur in the Milky Way Galaxy just about every year. It's rare to have a year without one happening in the Galaxy.
C) A Type II supernova is so faint that we miss most of the ones that happen in our Galaxy
D) A Type II supernova occurs at the end of the life of a star with 10 times the mass of our Sun or more
E) A Type II supernova is a less powerful explosion than any other type; it can't make any of the elements heavier than iron

Question 40

Your sweetheart gives you a piece of gold jewelry as a present to celebrate your passing your astronomy class. Where did the gold atoms in that gift originally come from (where were they most likely made)?

A) they were fused during the supergiant stage in the life of a massive star
B) they were built up from smaller nuclei during a supernova explosion
C) they were fused during the main sequence stage of a low-mass star
D) they were fused deep inside the hot core of the Earth a few million years ago
E) they were produced from other atoms in the cool outer envelopes of a red giant star

Question 41

When the BeppoSAX satellite, together with telescopes on the ground, helped astronomers pinpoint the location of the first gamma-ray burst to be identified with something that gave off visible light, the burst's location turned out to be in

A) at the center of the Milky Way Galaxy
B) just behind Jupiter volcanic moon Io
C) in the cloud of comets at the outskirts of our solar system
D) in a distant galaxy
E) at a random spot on the sky where nothing could be seen with visible light

Question 42

Which of the following statements about our best candidate for long-duration gamma-ray bursts is FALSE?

A) it involves the merger of two black holes
B) most of the bursts it causes can be shown to be in distant galaxies
C) the bursts it produces are more frequently seen and are brighter and easier to pinpoint
D) the mechanism involves a special type of supernova explosion
E) a rotating, magnetic star corpse most likely produces jets (or beams)

Question 43

How did observations with the Compton Gamma-ray Observatory show that gamma-ray bursts were not coming from the Milky Way Galaxy?

A) the bursts were all so "faint" (so little energy reached us) that they must be very far away
B) the gamma-rays were all Doppler shifted, showing the sources were moving very fast
C) the gamma-rays came from all over the sky, not just the plane of the Galaxy
D) the gamma-rays were seen mostly from the direction of the planets in our solar system
E) there were so few bursts observed with the Compton Observatory that it was not possible to figure out where they were coming from

Question 44

Astronomers now have a good idea for explaining how the short-duration gamma-ray bursts might come about. Which of the following is part of their explanation?

A) these bursts come from the clouds of comets that surrounds our solar system
B) these bursts most likely come from the merger of two neutron stars
C) these bursts involve a supernova explosion of a star that has lost its outer layer of hydrogen
D) these bursts should easily be observed to have "afterglows" in other wavelengths besides gamma-rays
E) these bursts are very common; most of the gamma-ray bursts are short-duration

Question 45

Astronomers have discovered pulsars spinning 500 x per second or more. How do astronomers think pulsars got to be spinning so outrageously fast?

A) Because the neutron stars that are the pulsars were small when they were born, all pulsars should be spinning this fast or faster
B) Such fast-spinning pulsars have companion stars near them, which dump material on the pulsar and that spins it faster and faster
C) Pulsars are planets very close to their stars, and they have to spin so fast so they don't fall in
D) Such pulsars were thrown out of their original location because the supernova explosion that produced them was not the same energy in all directions; this being pushed to one side made them spin faster
E) Astronomers have no suggestion for why such fast-spinning pulsars exist
Section 23.6: They Mystery of the Gamma-ray Bursts

Question 46

A rich donor to your college gets fascinated by gamma-ray bursts, and wants to give money to find out more about what produces them. Which of the following should her money go to fund?

A) a radio telescope, sensitive to the radiation given off by cold hydrogen
B) a gamma-ray telescope located on your campus, operated by graduate students
C) a network of visible-light telescopes which can automatically swing to a location provided by an alert system at NASA
D) a large infra-red telescope that is good at finding asteroids and comets at the outskirts of our solar system
E) the donor is too late; all the sources of gamma-ray bursts that we will ever see have already been identified

Question 47

In a Type Ia supernova, the cause of the violent outburst is:

A) the sudden emission of a shell of stellar material from a dying low-mass star
B) the collapse of a very massive protostar to the main sequence
C) an enormous release of neutrinos during a sudden episode of hydrogen fusion
D) the transfer of so much mass from a companion star that a white dwarf goes "over the limit" and collapses, causing an enormous amount of sudden fusion
E) two neutron stars colliding with each other

Question 48

A type Ia supernova involves the transfer of mass from one star to a companion white dwarf? Yet, in some cases, astronomers cannot locate a star near where they see Type Ia explosions. How do they explain the absence of a companion star?

A) they suggest that the companion star is a black hole
B) they suggest that the companion star is always of such low mass, it's easy to miss
C) they suggest that some type Ia supernova are caused by the collision of two white dwarfs, both of which then explode
D) they suggest that some type Ia supernova explosions come from a single massive star where the fusion of iron causes a catastrophe and great release of neutrinos
E) no one has any idea how to explain type Ia supernovae which do not leave behind a companion star; it's an unsolved mystery