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Q: Most pulsars are observed only as ________ sources. A) gamma-ray burster B) visible lighthouse C) ultraviolet repeating D) radio E) X-ray
Q: Which of these does not exist? A) a million solar mass black hole B) a 6 solar mass black hole C) a 1.8 solar mass neutron star D) a 1.5 solar mass white dwarf E) a 0.06 solar mass brown dwarf
Q: The mass range for neutron stars is A) 0.08 to 0.4 solar masses. B) 0.4 to 3 solar masses. C) 1.4 to 3 solar masses. D) 3 to 8 solar masses. E) 6 to 11 solar masses.
Q: An object more massive than the Sun, but roughly the size of a city, is a A) black dwarf. B) white dwarf. C) brown dwarf. D) neutron star. E) red dwarf.
Q: Two important properties of young neutron stars are A) extremely slow rotation and a strong magnetic field. B) extremely rapid rotation and a weak magnetic field. C) extremely rapid rotation and a strong magnetic field. D) no rotation and a weak magnetic field. E) no rotation and no magnetic field.
Q: In a neutron star, the core is A) made of compressed neutrons in contact with each other. B) electrons and protons packed so tightly they are in contact. C) constantly expanding and contracting. D) primarily iron and silicon. E) no longer rotating.
Q: The closer the observer comes to the event horizon, the slower his watch will appear to run to a distant observer.
Q: The presently known laws of physics clearly describe the conditions inside a black hole's event horizon.
Q: Even if a probe were in a stable orbit near a black hole, we would still observe its signals red shifted by the gravitational field of the black hole.
Q: Because of their immense size, black holes moving through space consume huge quantities of interstellar matter along their paths.
Q: Einstein's prediction of the curvature of space was confirmed by the 1919 total solar eclipse.
Q: No communication is possible across an event horizon.
Q: Both space and time are warped near the strong gravitational fields of neutron stars and black holes.
Q: Special relativity says that c, the speed of light, is the maximum velocity for both matter and energy in our universe.
Q: The Schwarzschild radius of a black hole is about 3 km per solar mass.
Q: All Type II supernovae produce neutron stars when they collapse.
Q: The escape speed at the event horizon of a black hole is c, 300,000 km/sec.
Q: Any main-sequence star over 25 solar masses will probably retain enough matter in its core after its supernova to make a black hole.
Q: Only high-energy gamma rays can escape the event horizon of a black hole.
Q: Some gamma-ray bursters may be due to the merger of a neutron star and a black hole.
Q: All gamma-ray bursters have the same fundamental driving mechanism, although we don't yet know whether it is a hypernova or a merger of two neutrons stars.
Q: All the gamma-ray bursters measured to date have distances of millions or even billions of light years.
Q: No optical traces have been found of the gamma-ray bursters.
Q: Gamma-ray bursters seem scattered randomly over the entire sky.
Q: Gamma-ray bursters are all found to be within our galaxy.
Q: A hypernova is a gamma-ray burster that forms a black hole as well.
Q: An X-ray burster is similar to a nova.
Q: Millisecond pulsars are never members of close binary systems.
Q: Planets similar to our terrestrials have been found orbiting pulsars.
Q: No planets have ever been found around any pulsars.
Q: While most pulsars slow down over time, millisecond pulsars spin faster due to mass transfer from a close companion.
Q: Planet-sized bodies have been detected around pulsars.
Q: All neutron stars seen from Earth are pulsars.
Q: The pulses from a pulsar are most likely coming from localized areas near the magnetic poles.
Q: Pulsars are created in a Type I supernova.
Q: Most pulsars are known only as radio sources, but a few of the younger ones, like the Crab and Vela, also give off visible and even X-ray energy.
Q: The "pulse" from a pulsar is due to the rapidly expanding and contracting outer shell of the star.
Q: Newly-formed neutron stars start with weak magnetic fields, but they strengthen over time into pulsars.
Q: In a neutron star, the electrons in the core are all in contact with each other.
Q: A neutron star is what remains after a Type II supernova explosion has destroyed the rest of the star.
Q: Stars of less than 8 solar masses will not go supernova.
Q: Neutron stars are 100,000 times denser than white dwarfs.
Q: In a neutron star, the protons and electrons are fused together, leaving only neutrons.
Q: Why is Cygnus X-1 considered such a good black hole candidate?
Q: Describe the range of sizes and masses of black holes.
Q: How were the three planets orbiting the millisecond pulsar found?
Q: List the three types of objects a star's core can collapse to, and give the mass limits for each.
Q: Contrast X-ray bursters with nova events.
Q: Why do the millisecond pulsars violate the usual rotation pattern for pulsars?
Q: What evidence is there linking the Crab nebula to a supernova?
Q: What does it take to allow us to observe a neutron star as a pulsar?
Q: How can prolonged observations of pulsars yield their approximate age?
Q: Describe changes in atomic structure that accompany the making of neutron star.
Q: A white dwarf's atoms have their electron orbitals crushed as closely as the Exclusion Principle allows.
Q: Although mass transfer can occur in binary stars, the small mass change does not impact the evolution of either companion.
Q: Like emission nebulae, planetary nebulae glow because hot stars are causing the gases to ionize when exposed to strong ultraviolet radiation.
Q: Compared to the interstellar medium, the gases in a planetary nebula will be richer in helium and carbon.
Q: While there are none yet, in the very distant future, most normal matter will be in the form of black dwarfs.
Q: As their name implies, all planetary nebulae feature spherical shells and look like the disks of Uranus or Neptune.
Q: Our Sun will first become a red giant, then a white dwarf, and finally a brown dwarf.
Q: Today the majority of the mass of the universe is already in the form of black dwarfs, the solution to the "dark matter" problem.
Q: The nova event is created by the helium flash.
Q: The density of white dwarf stars is about a million times that of the Sun.
Q: Our Sun will never become hot enough for carbon nuclei to fuse.
Q: Our Sun will eventually become a nova.
Q: A star system may undergo two or more nova outbursts.
Q: Our Sun should become a planetary nebula in another five billion years.
Q: All stars have roughly the same luminosity after the helium flash.
Q: Low-mass stars may become hundreds of times more luminous as giants than they were on the main sequence.
Q: A typical star burns helium for about the same amount of time it burns hydrogen.
Q: Our Sun will fade in luminosity as its supply of hydrogen drops in a billion years.
Q: The helium flash shows up on the H-R diagram on the way to the horizontal branch.
Q: A star may undergo two or more red giant expansion stages.
Q: The luminosity of the red giant during its second trip to the upper right on the H-R diagram is less than before the helium flash expansion.
Q: The helium flash increases the star's luminosity.
Q: The helium flash stage lasts several thousand years.
Q: Once the helium flash occurs at stage 10, the star stabilizes again on the horizontal branch of the H-R diagram, but now hundreds of times as bright as on the main sequence.
Q: Paradoxically, while the core of the red giant is contracting and heating up, its radiation pressure causes its photosphere to swell up and cool off.
Q: The initial rise off the main sequence in stage 8 comes from gravitational energy of the contracting helium core.
Q: The main reason that stars evolved off the main sequence is because they are becoming less massive as energy is lost into space from the proton-proton cycle.
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