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Chapter 16
Stardeath
1. You are comparing a white dwarf, neutron star, and brown dwarf. What is the order of their
sizes, from SMALLEST to LARGEST?
A. Brown dwarf, neutron star, white dwarf.
B. Neutron star, brown dwarf, white dwarf.
C. Neutron star, white dwarf, brown dwarf.
D. White dwarf, brown dwarf, neutron star.
2. The outward force keeping a degenerate white dwarf star from collapsing is:
A. degenerate electron "gas" pressure.
B. internal pressure from heat.
C. its rapid spinning.
D. pressure from the outward flow of neutrinos.
3. The belief that pulsars are rapidly-rotating neutron stars arises most strongly from the:
A. power of their pulses.
B. regularity of their pulses.
C. very short pulse periods of the fastest pulsars.
D. detection of their pulses at radio wavelengths.
4. You are comparing a typical nova explosion with a supernova. Which is NOT true?
A. Novas almost always occur in binary stars.
B. Novas involve explosions of the surface layers.
C. Novas leave behind most of the mass of the star.
D. Novas are initially brighter than supernovas, but don't last as long.
5. In the binary star model for nova explosions, the fuel from the explosion:
A. flows from a companion star to a white dwarf.
B. flows from a companion star to a neutron star.
C. flows from a companion star into a black hole.
D. falls in from interstellar space.
6. Which statement about a type II supernova is FALSE?
A. It involves a massive, Population I star.
B. It blows off a large fraction of the star's mass.
C. It leaves behind a white dwarf of about two solar masses.
D. It peaks about a month after the explosion begins.
7. Which of these is NOT true about the Crab Nebula?
A. Doppler shift observations show the filaments expanding.
B. A pulsar lies in its center.
C. The 1054 A.D. supernova occurred at the same place.
D. The pulsar is spinning faster as the nebula expands.
8. In order to produce synchrotron emission, you need:
A. a source of high-speed electrons and lots of dust.
B. fairly strong magnetic fields and high speed electrons.
C. extremely hot hydrogen to produce the emission lines.
D. intense magnetic fields and fission of uranium nuclei.
9. An observer who, at a safe distance, watches an astronaut travel toward and into a black hole will
see:
A. the astronaut reach the singularity in a short time.
B. the astronaut never crossing the Schwarzschild radius.
C. light flashes from the astronaut blue shifted.
D. light flashes arrive more and more rapidly.
10. According to Einstein's general theory of relativity, what will happen to an object thrown into a
black hole after it crosses the Schwarzschild radius?
A. It is crushed into a singularity and trapped forever.
B. It is thrown back at the speed of light
C. It will eventually be recycled as antimatter.
D. It will be ejected as material in the bipolar jets.
11. Which of the following are thought to be made ONLY in a supernova explosion?
A. Iron.
B. Oxygen.
C. Carbon.
D. Uranium.
12. The highest energy cosmic rays typically:
A. are protons travelling at close to the speed of sound.
B. are electrons travelling at close to the speed of light
C. are positrons travelling at close to the speed of light
D. are protons travelling at close to the speed of light
13. One model for X-ray burstars involves:
A. matter accreting around a black hole.
B. an accretion disk around a white dwarf in a binary.
C. matter falling onto a neutron star in a binary.
D. rapid rotation of a neutron star.
14. Cygnus X-1 is one of the best candidates for a black hole. Which of the following observations
is NOT used to infer this?
A. Cygnus X-1 emits a lot of X-rays.
B. The optical companion is a massive blue supergiant star.
C. Doppler shifts indicate an orbital period of 5.6 days.
D. It is located in the constellation of Cygnus.
15. In the inverse beta decay process during stardeath, we see copious production of:
A. neutrinos.
B. pions.
C. electrons.
D. protons.
16. Why is it that a supernova from a very massive star can produce a black hole instead of a
neutron star?
A. Because of the intense magnetic fields.
B. Because the gravitational pressure overcomes the neutron degeneracy pressure.
C. Because the neutron escape velocity is exceeded.
D. Because the gravitational pressure crushes the electron orbitals.
17. Which of these is NOT a property of black holes?
A. They have infinite density.
B. They have no spacial extent.
C. They have the capacity to warp spacetime to a singular point.
D. They contain between 1.5 and 2 solar masses.
18. Consider the end of a star's life. If it is like our sun, it will finish burning off hydrogen, blow off
its envelope, and leave a carbon core that is hot but not nearly as luminous as the giant stage
previously. These objects are called:
A. supernovae.
B. eclipsing binary stars.
C. white dwarfs.
D. brown dwarfs.
19. In the binary-star model for nova explosions, the fuel from the explosion:
A. flows from a companion star to a white dwarf.
B. flows from a neutron star to the companion star.
C. flows from a companion star into a black hole.
D. comes from the interstellar medium.
20. Cool ________ are red,
Hot __________ are blue.
If you answer this question correctly,
I'll give one point to you.
A. black holes/white dwarfs
B. white dwarfs/binaries
C. supergiants/white dwarfs
D. brown dwarfs/pulsars
21. In a binary star system, the region around each star where gravitational force dominates is
called the:
A. Roche lobe.
B. light radius.
C. corotational radius.
D. synchrotron region.
22. When did the burst of neutrinos from SN1987A arrive?
A. One week after it became visible.
B. One week before it became visible.
C. Several hours before it became visible.
D. Three days after it became visible.
23. In beta decay, a neutron under normal conditions of low pressure will disintegrate in:
A. less than 10 minutes.
B. less than one minute.
C. more than one hour.
D. less than 10 nanoseconds.
24. During the burning of a Red Supergiant and during a Supernova explosion, nucleosynthesis
takes place. The process that synthesizes heavy elements is:
A. gravitational attraction.
B. bombardment of nuclei by high-energy neutrons.
C. bombardment of neutrons by neutrinos.
D. fission of iron into alpha particles.
25. The "rapid process" and "slow process" contribute to the buildup of heavy nuclei. If the neutron
capture rate is slower than the beta-decay rate, __________ are formed.
A. proton-rich nuclei
B. neutron-rich nuclei
C. electron-rich nuclei
D. less massive nuclei
26. In the Lighthouse Model of pulsar emission, the _________ may be due to polar emission of
photons and particles that are not exactly aligned with the observational direction.
A. primary pulse
B. major pulse
C. inter-pulse
D. secondary pulse
27. Which of these is a potential type I supernova?
A. A red giant transferring mass to a 1.3 solar mass white dwarf.
B. A red giant making silicon in its core.
C. The superhot central star of a planetary nebula.
D. A rapidly spinning neutron star.
28. Which of these is a potential type II supernova?
A. A red giant transferring matter onto a 1.3 solar mass white dwarf.
B. A red supergiant ready to make iron in its core.
C. The superhot central star of a planetary nebula.
D. A rapidly spinning neutron star.
29-32. Match the approximate dimensions with these objects:
A. Manhattan.
B. Earth.
C. A few light months.
D. 170,000 ly.
29. Distance to Supernova 1987A.
30. A white dwarf like Sirius B.
31. A neutron star such as in the Crab Nebula.
32. Present dimensions of Supernova 1987A's remnant
33. Based on the historical records, supernovas visible with the naked eye happen in the Milky Way
about every:
A. few years.
B. few decades.
C. few centuries.
D. 200,000 years.
ESSAYS
1. Describe the rearrangement of atoms during a stellar core's collapse into a white dwarf.
2. Describe the rearrangement of the atoms during the collapse of a supermassive Star's core into a
neutron star.
3. Given that Deneb is about 5Ox as massive as the Sun, yet 50,000x as luminous, compare its
expected main sequence lifetime with the Sun's predicted 10 billion years.
4. Given time, what will happen to the pulse rate and strength of the pulsar? Why? Describe how
this could be used to match an observed pulsar with a historical observation of a supernova, such as
the one of 1054 A.D.
5. Use the stages and time spans of the life of a massive star to explain why gold is rare, yet iron is
quite common.
6. Why is the supernova stage so important in understanding the chemical difference between
terrestrial and jovian planets? .
7. Why is the supernova stage so important in understanding the chemical differences between the
two stellar populations?