HW3 Name MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) A surface explosion on a white dwarf, caused by falling matter from the atmosphere of its binary companion, creates what kind of object? A) hypernova B) type II supernova C) nova D) type I supernova E) gamma ray burstar 1) 2) Neutron stars and black holes are formed by: 2) A) novae. B) mass transfer in binary star systems. C) type II supernovae. D) the star formation process. E) type I supernovae. 3) In a neutron star, the core is: 3) A) constantly expanding and contracting. B) no longer rotating. C) electrons and protons packed so tightly they are in contact. D) made of compressed neutrons in contact with each other. E) primarily iron and silicon. 4) Two important properties of young neutron stars are: 4) A) no rotation and no magnetic field. B) extremely slow rotation and a strong magnetic field. C) extremely rapid rotation and a weak magnetic field. D) extremely rapid rotation and a strong magnetic field. E) no rotation and a weak magnetic field. 5) Neutron stars have: 5) A) monopolar fields that switch polarity every rotation. B) no relation to pulsars. C) very strong bi-polar magnetic fields. D) periods of days or weeks. E) weak or non-existent magnetic fields. 6) An object more massive than the Sun, but roughly the size of a city, is a: 6) A) neutron star. B) white dwarf. C) brown dwarf. D) supernova remnant. E) red dwarf. 7) What would happen if mass is added to a 1.4 solar mass white dwarf? 7) A) The core would collapse as a type II supernova. B) The star would explode as a nova. C) The star's radius would increase. D) The star would erupt as a carbon detonation (type I) supernova. E) The star would immediately collapse into a black hole.
8) The average density of neutron stars approaches: 8) A) about 1017 kg/m3, similar to the density of atomic nuclei. B) a million times that of normal matter. C) about 1018 times that of water. D) infinity. E) a million times that of even a white dwarf. 9) Pulsars: 9) A) spin very rapidly when they're young. B) are the cause of gamma-ray bursts. C) generally form from 25 solar mass stars. D) emit radio in all directions. E) spin very slowly when they're young, and gradually spin faster as they age. 10) Neutron stars do NOT have: 10) A) masses greater than 1.4 solar masses. B) sizes comparable to large cities. C) large surface gravities, compared to the Sun. D) rotation periods comparable to the Sun's. E) strong magnetic fields. 11) Which of these does NOT exist? 11) A) a 6.8 solar mass neutron star B) a 0.06 solar mass brown dwarf C) a 6 solar mass black hole D) a 1.0 solar mass white dwarf E) a million solar mass black hole 12) The vast majority of pulsars are known only from their pulses in: 12) A) microwaves. B) radio waves. C) gamma-rays. D) visible light. E) X-rays. 13) What compelling evidence links pulsars to neutron stars? 13) A) Both pulsars and neutron stars have been discovered near the Sun. B) Only a small, very dense source could rotate that rapidly without flying apart. C) Both pulsars and neutron stars can be found in globular star clusters. D) Pulsars are always found in binary systems with neutron stars. E) Pulsars are known to evolve into neutron stars. 14) What makes the Crab pulsar somewhat unusual among pulsars in general? 14) A) It is rather bright at visible wavelengths. B) It is the oldest pulsar observed. C) Its period is not regular like other pulsars. D) It is the most intense source of X-rays in the sky. E) It is the fastest pulsar known. 15) What makes the Crab Nebula supernova remnant unusual as a supernova remnant? 15) A) It is the remnant of a supernova that was observed in the 20th century.
B) It is the biggest supernova remnant visible. C) It is the remnant of a supernova observed by humans. D) It is the nearest supernova remnant. E) It is the oldest supernova remnant known. 16) In the Lighthouse Model, 16) A) all pulsars must have their poles pointed directly toward us. B) the star literally turns on and off like a lighthouse beacon. C) if the beam sweeps across us, we will detect a pulse of radiation. D) the period of pulsation must speed up as the neutron star continues collapsing. E) the period of pulsation slows down due to the drag of the remnant on its field. 17) In the Lighthouse model: 17) A) pulsars are observable only if they lie in the galactic plane. B) if the beams sweeps across us, we can observe the pulse. C) all pulsars have their poles pointed directly at us or they would be not observable. D) pulsars are navigational devices created by interstellar navigators as discovered by Jocelyn Bell in 1967. E) the period of pulsation must speed up as the neutron star continues contracting. 18) Which of the following is NOT a property of a pulsar? 18) A) each pulse consisting of a 0.01 second burst of radiation B) over time, the period is gradually increasing C) emissions only in the visible part of the spectrum D) period of 1.34 seconds E) time interval between pulses is very uniform 19) Whose work with SETI led to the discovery of pulsars in 1967? 19) A) Jocelyn Bell B) Sir Bernard Lovell C) Martin Schwarzschild D) Anthony Hewish E) Stephen Hawking 20) The supernova of 1054 AD produced: 20) A) a pulsar with a period of 33 milliseconds, visible optically. B) no remaining visible trace, as it was a type I supernova. C) a remnant still visible to the naked eye, the Crab Nebula, M-1. D) the closest known neutron star to our Sun. E) the most famous black hole. 21) While most neutron stars are also pulsars, an older "bare" neutron star was captured in rapid motion only 200 lightly years distant by: A) the Chandra X-ray observatory. B) the Spitzer Infrared Space Telescope. C) Arecibo Radio Observatory. D) the Keck Telescopes used as an interferometer. E) the Hubble Space Telescope. 21) 22) The Chandrasekhar mass limit is: 22) A) 3 solar masses. B) 8 solar masses.
C).08 solar masses. D) 1.4 solar masses. E).4 solar masses. 23) For a nova to occur, the system must have already been a(n): 23) A) mass-transfer binary. B) eclipsing binary. C) astrometric binary. D) detached binary. E) spectroscopic binary. 24) The total energy emitted by the brightest nova explosions is about: 24) A) 1,000 Suns. B) a billion Suns. C) a trillion Suns. D) a million Suns. E) 50,000 Suns. 25) An iron core cannot support a star because: 25) A) iron has poor nuclear binding energy. B) iron is the heaviest element, and sinks upon differentiation. C) iron supplies too much pressure. D) iron is in the form of a gas, not a solid, in the center of a star. E) iron cannot fuse with other nuclei to produce energy. 26) Beyond the formation of iron, nuclear energy can be produced only by: 26) A) fission of heavy nuclei back toward lighter ones. B) fusion of still heavier elements. C) the dark force. D) ionization of the radioactive nuclei. E) gravity. 27) When a stellar iron core collapses, large numbers of neutrinos are formed, and then: 27) A) they are captured to form heavy elements. B) they form the neutron star. C) they are captured to form light elements. D) they immediately pass through the core and escape to space. E) they are absorbed by electrons to produce positrons. 28) Most of the energy of the supernova is carried outward via a flood of: 28) A) helium nuclei. B) positrons. C) gamma rays. D) neutrinos. E) protons. 29) In neutronization of the core, a proton and an electron make a neutron and a(n): 29) A) neutrino. B) pion. C) antineutron. D) positron. E) muon.
30) A 20 solar mass star will stay on the main sequence for 10 million years, yet its iron core can exist for only a: A) month. B) century. C) day. D) year. E) week. 30) 31) The element with the most stable nucleus and smallest mass per particle is: 31) A) argon. B) hydrogen C) uranium. D) helium. E) iron. 32) As a star's evolution approaches the Type II supernova, we find: 32) A) the heavier the element, the less time it takes to make it. B) the heavier the element, the higher the temperature to fuse it. C) photodisintegration of iron nuclei begins at 10 billion K to ignite the supernova. D) helium to carbon fusion takes at least 100 million K to start. E) All of the above are correct. 33) At temperatures of K, photons can split apart nuclei until only protons and neutrons are left in photodisintegration. A) ten billion B) ten million C) one billion D) one hundred billion E) 100 million 33) 34) The core of a highly evolved high mass star is a little larger than: 34) A) Earth. B) a white dwarf. C) our Sun. D) our solar system. E) Jupiter. 35) What made supernova 1987a so useful to study? 35) A) Its progenitor had been observed previously. B) We saw direct evidence of nickel to iron decay in its light curve. C) It occurred after new telescopes, such as Hubble, could observe it very closely. D) In the Large Magellanic Cloud, we already knew its distance. E) All of the above are correct. 36) Where was supernova 1987a located? 36) A) in the Orion Nebula, M-42 B) near the core of M-31, the Andromeda Galaxy C) in M-13, one of the closest of the evolved globular clusters D) in our companion galaxy, the Large Magellanic Cloud E) in Sagittarius, near the Galactic Nucleus 37) Why are neutrinos from a type II supernova detected before photons? 37) A) Neutrinos are easier to detect than photons. B) Neutrinos travel faster than photons. C) Neutrinos are emitted from the outer part of the star; photons come from the core. D) Neutrinos escape from the star quickly because they hardly interact with matter; photons are delayed by interactions with matter. E) Neutrinos are produced in the explosion before photons.
38) A star can be a supernova: 38) A) only once. B) in predictable cycles of decades. C) before it reaches the main sequence, if it is massive enough. D) only if it can fuse iron in its core. E) a few times, at unpredictable intervals. 39) What evidence is there that supernovae really have occurred? 39) A) supernova remnants B) observations of the actual explosions C) Crab Nebula D) existence of heavy radioactive elements in nature E) All of the above. 40) The supernova that formed M-1, the Crab Nebula, was observed in: 40) A) 1572 AD by Tycho Brahe. B) 1054 AD by Chinese and Middle Eastern astronomers. C) 1006 by observers in the southern hemisphere. D) about 9,000 BC by all our ancestors. E) 1604 AD by Johannes Kepler.