chapter 23

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 Submit Your Answer

. smaller in diameter

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 Correct Response 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 Submit Your Answer

. 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

What is the expected main sequence lifetime of Wolf 359, a very dim star having 10 per cent of the Sun's mass? Correct Response 3.2 x 1012 years 3.2 x 107 years 3.2 x 109 years 1.6 x 1010 years Submit Your Answer

3.2 x 1012 years

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: Correct Response 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 Submit Your Answer

a. a neutron star

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

Which of the following statements about Supernova 1987A is FALSE? Correct Response 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 Submit Your Answer

a. it exploded relatively close to us, in a spiral arm of the Milky Way Galaxy

30. 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? Correct Response 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 Submit Your Answer

a. the production of huge numbers of neutrinos

When a single star with a mass equal to the Sun dies, it will become a Correct Response a. white dwarf b. neutron star c. black hole d. pulsar e. burster

a. white dwarf

The astrophysicist who first calculated the highest mass that a dying star can have and still be a white dwarf was a. H. R. Russell b. S. Chandrasekhar c. I. Shelton d. A. Hewish e. D. Generate Submit Your Answer

b. S. Chandrasekhar

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 Correct Response 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 Submit Your Answer

b. as the star is dying, a considerable part of its mass will be lost into space

n 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) Correct Response 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 Submit Your Answer

b. because neutron star beams come out of the north and south poles of a magnetic field

Which of the following is the smallest? a. white dwarf Correct Response b. neutron star c. red giant d. main sequence star e. protostar Submit Your Answer

b. neutron star

What kind of telescope did Jocelyn Bell use to discover pulsars in 1968? a. visible light Correct Response b. radio c. ultraviolet d. x-ray e. neutrino Submit Your Answer

b. radio

Astronomer have concluded that pulsars are a. rotating black holes Correct Response b. rotating neutron stars c. rotating red giants d. supernovae that are about to explode e. protostars that are collapsing and spinning very rapidly Submit Your Answer

b. rotating neutron stars

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 Correct Response 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 Submit Your Answer

b. the fusion of iron

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 Correct Response 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 Submit Your Answer

b. they were built up from smaller nuclei during a supernova explosion

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 Correct Response c. a neutron star is slowing down (losing rotation energy) d. large parts of the nebula are falling inward, releasing gravitational energy e. the Crab nebula is a signal station, where some aliens (LGM) are broadcasting beats for rap music Submit Your Answer

c. a neutron star is slowing down (losing rotation energy)

Elements heavier than iron can be created during: a. the big bang b. the main sequence Correct Response 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 Submit Your Answer

c. a supernova explosion

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 Correct Response 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 Submit Your Answer

c. inside, there are a number of newly formed massive stars (O and B type stars)

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 Correct Response c. neutrino d. radio wave e. nucleus of iron Submit Your Answer

c. neutrino

Which of the following is the largest (in diameter)? a. neutron star b. white dwarf Correct Response c. red giant d. main sequence star e. the cloud of fossil-fuel pollution around Bayonne, New Jersey Submit Your Answer

c. red giant

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 Correct Response 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 Submit Your Answer

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

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 Correct Response 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 Submit Your Answer

c. the cosmic rays produced by supernova explosions would have contributed to the rate of mutations over many generations

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 Correct Response 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) Submit Your Answer

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

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 Correct Response 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 Submit Your Answer

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

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 Correct Response d. a neutron star e. you can't fool me, his weight would be the same on all of the above objects Submit Your Answer

d. a neutron star

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 Correct Response 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 Submit Your Answer

d. after a white dwarf cools off it becomes too cold and dark to emit visible light

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 Correct Response d. explodes outward as a supernova e. continues regular fusion and returns to the main sequence Submit Your Answer

d. explodes outward as a supernova

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 Correct Response d. infrared e. very long wavelength radio waves Submit Your Answer

d. infrared

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 Correct Response 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 Submit Your Answer

d. the electrons get as close to each other as possible and resist further compression

A neutron star is as dense as a. water b. the center of the Earth c. a white dwarf star Correct Response d. the nucleus of an atom e. our astronomy textbook Submit Your Answer

d. the nucleus of an atom

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 Correct Response d. white dwarf e. supernova Submit Your Answer

d. white dwarf

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 Correct Response e. a few tenths of a second Submit Your Answer

e. a few tenths of a second

4. 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 Correct Response e. all the above Submit Your Answer

e. all the above

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 Correct Response 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 Submit Your Answer

e. astronomers have actually only found one neutron star and that was discovered very close to us and by sheer luck

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 Correct Response e. from the Doppler shift in the line radiation from the nebula Submit Your Answer

e. from the Doppler shift in the line radiation from the nebula

The most stable (tightly bound) atomic nucleus in the universe is: a. hydrogen b. carbon c. uranium d. technetium Correct Response e. iron Submit Your Answer

e. iron

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 Correct Response e. neutrinos Submit Your Answer

e. neutrinos

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 Correct Response e. the neutron star is disrupted and tears apart into many pieces Submit Your Answer

e. the neutron star is disrupted and tears apart into many pieces

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 Correct Response 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 Submit Your Answer

the pulsar beam doesn't happen to point toward us in many cases