Astronomy Ch. 21 Stellar Explosions. MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

Transcription

1 Name: Period: Date: Astronomy Ch. 21 Stellar Explosions 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) type I supernova B) nova C) type II supernova D) hypernova E) gamma ray burstar 1) 2) The Chandrasekhar mass limit is A) 1.4 solar masses. B).08 solar masses. C) 8 solar masses. D) 3 solar masses. E).4 solar masses. 2) 3) For a nova to occur, the system must have already been a A) detached binary. B) astrometric binary. C) eclipsing binary. D) mass-transfer binary. E) spectroscopic binary. 3) 4) The total energy emitted by the brightest nova explosions is about A) a trillion Suns. B) 50,000 Suns. C) a million Suns. D) 1,000 Suns. E) a billion Suns. 4) 5) An iron core cannot support a star because A) iron is in the form of a gas, not a solid, in the center of a star. B) iron is the heaviest element, and sinks upon differentiation. C) iron supplies too much pressure. D) iron cannot fuse with other nuclei to produce energy. E) iron has poor nuclear binding energy. 5) 6) Beyond the formation of iron, nuclear energy can be produced only by A) fusion of still heavier elements. B) the dark force. C) ionization of the radioactive nuclei. D) gravity. E) fission of heavy nuclei back toward lighter ones. 6) 1

2 7) When a stellar iron core collapses, large numbers of neutrinos are formed, then: A) they are absorbed by electrons to produce positrons. B) they form the neutron star. C) they are captured to form light elements. D) they are captured to form heavy elements. E) they immediately pass through the core and escape to space. 7) 8) Most of the energy of the supernova is carried outward via a flood of A) helium nuclei. B) neutrinos. C) gamma rays. D) protons. E) positrons. 8) 9) In neutronization of the core, a proton and an electron make a neutron and a A) pion. B) antineutron. C) neutrino. D) muon. E) positron. 9) 10) 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) day. B) week. C) century. D) month. E) year. 10) 11) As a star's evolution approaches the Type II supernova, we find A) the heavier the element, the higher the temperature to fuse it. B) the heavier the element, the less time it takes to make 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. 11) 12) At temperatures of K, photons can split apart nuclei until only protons and neutrons are left in photodisintegration. A) 100 million B) one billion C) ten billion D) ten million E) one hundred billion 12) 13) What made supernova 1987a so useful to study? A) We saw direct evidence of nickel to iron decay in its light curve. B) In the Large Magellanic Cloud, we already knew its distance. C) It occurred after new telescopes, such as Hubble, could observe it very closely. D) Its progenitor had been observed previously. E) All of the above are correct. 13) 2

3 14) Where was supernova 1987a located? A) in Sagittarius, near the Galactic Nucleus B) in the Orion Nebula, M-42 C) in our companion galaxy, the Large Magellanic Cloud D) near the core of M-31, the Andromeda Galaxy E) in M-13, one of the closest of the evolved globular clusters 14) 15) A star can be a supernova A) only if it can fuse iron in its core. B) in predictable cycles of decades. C) a few times, at unpredictable intervals. D) only once. E) before it reaches the main sequence, if it is massive enough. 15) 16) What evidence is there that supernovae really have occurred? A) existence of heavy radioactive elements in nature B) Crab Nebula C) observations of the actual explosions D) supernova remnants E) all of the above 16) 17) The supernova that formed M-1, the Crab Nebula, was observed in A) about 9,000 BC by all our ancestors. B) 1054 AD by Chinese and other oriental and mid eastern astronomers. C) 1006 by observers in the southern hemisphere. D) 1572 AD by Tycho Brahe. E) 1604 AD by Johannes Kepler. 17) 18) What is the amount of energy emitted in the form of neutrinos, during a supernova explosion, compared to the amount of energy radiated as electromagnetic radiation? A) only.007 as much B) 100 times more C) about twice as much D) ten times more E) about equal amounts 18) 19) What produces a type-i supernova? A) the collapse of the core of a massive star B) the radioactive decay of nickel 56 into cobalt 56 into iron 56 C) a nova igniting a helium flash in its red giant companion D) the helium flash blows apart a giant's core E) mass transfer onto a white dwarf pushing it over 1.4 solar masses 19) 20) Which of these is the likely progenitor of a type I supernova? A) a helium-neon white dwarf B) an evolved red giant which is just starting to make silicon in its core C) a contact binary, with the neutron star at 2.3 solar masses D) an evolved blue supergiant that is about to experience the helium flash E) a mass-transfer binary, with the white dwarf already at 1.3 solar masses 20) 3

4 21) Which of these is the likely progenitor of a type II supernova? A) two white dwarfs in a contact binary system B) a mass-transfer binary, with the white dwarf already at 1.3 solar masses C) a contact binary, with the neutron star at 2.3 solar masses D) an evolved blue supergiant that is about to experience the helium flash E) an evolved red giant which is just starting to make silicon in its core 21) 22) The Chandrasekhar Limit is A) the temperature at which helium fusion starts. B) the point at which a planetary nebula forms. C) the lower mass limit for a Type II supernova. D) the upper mass limit for a white dwarf. E) the temperature at which hydrogen fusion starts. 22) 23) If it gains sufficient mass, a white dwarf can become a A) type I supernova. B) type II supernova. C) planetary nebula. D) brown dwarf. E) black dwarf. 23) 24) For a white dwarf to explode entirely as a Type I supernova, it's mass must be A) 3 solar masses, the Schwartzschild Limit. B) 20 solar masses, the Hubble Limit. C) 100 solar masses, the most massive known stars. D) 1.4 solar masses, the Chandrasekhar Limit. E) at least 0.08 solar masses. 24) 25) Which of these events is not possible? A) a white dwarf being found in the center of a planetary nebula B) close binary stars producing recurrent novae explosions C) low-mass stars swelling up to produce planetary nebulae D) red giants exploding as Type II supernovae E) white dwarfs and companion stars producing recurrent Type I supernova events 25) 26) Which of these does not depend on a close binary system to occur? A) a nova B) a Type II supernova C) a Type I supernova D) All of these need mass transfer to occur. E) None of these depend on mass transfer. 26) 27) What can you conclude about a Type I supernova? A) It was originally a high mass star. B) The star never reached the Chandrasekhar Limit. C) Its spectrum will show large amounts of hydrogen. D) Its core was mostly iron. E) It was originally a low-mass star. 27) 4

5 28) In order of visual luminosity at the start, which is most luminous? A) a planetary nebula B) a type II supernova C) a nova D) a type I supernova E) a red supergiant 28) 29) The Chandrasekhar limit is A) the lower mass limit for a supernova. B) the upper mass limit for a white dwarf. C) the temperature at which helium fusion starts. D) the point at which a planetary nebula forms. E) the temperature at which hydrogen fusion starts. 29) 30) Type I supernovae are NOT A) brighter than type II supernovae. B) created by carbon detonation. C) created by the mass of the white dwarf exceeding Chandrasekhar's Limit. D) products of mass transfer. E) rich in hydrogen from the outer envelope of the collapsed star. 30) 31) Supernova remnants differ from star forming regions because, although there is ionized hydrogen in both, supernova remnants A) are more diffuse than star forming regions. B) are located far from star forming regions. C) don't look like star forming regions. D) are much bigger than star forming regions. E) contain no ionizing stars. 31) 32) Which of these is NOT true about supernovae? A) The one in 1987 in the Large Magellanic Cloud was of type II. B) Type I involves carbon detonation. C) Type II involves formation of iron in the core. D) Neutronization is vital in understanding type II core collapse. E) The two types are both closely related to evolution of white dwarfs. 32) 33) A recurrent nova could eventually build up to a A) Type II supernova. B) Type I supernova. C) quasar. D) planetary nebula. E) hypernova. 33) 34) Nearly all the elements found in nature were formed inside stars, except for A) helium and carbon. B) hydrogen and helium. C) uranium and radium. D) silver and technetium. E) carbon and silicon. 34) 5

6 35) What is stellar nucleosynthesis? A) The formation of white dwarfs, neutron stars, and black holes from stars. B) The formation of planetary nebulae by red giants. C) The formation of stars from a nucleus of contracting material. D) The process by which stars form interstellar dust. E) The formation of heavier elements inside stars. 35) 36) The heaviest nuclei of all are formed A) during carbon burning in the giant stage. B) during a carbon detonation supernova. C) during the triple alpha process. D) by neutron capture during a type II supernova explosion. E) during a nova explosion. 36) 37) What direct evidence do astronomers have that supports the heavy element formation in stars? A) observed elemental abundances B) gamma-ray emissions from decay of cobalt 56 in supernovae C) the presence of technetium in giant star spectra D) light curves of type-i supernovae E) All of the above are evidence of this. 37) 38) Why does neutron capture work? A) Neutrons have no repulsive barrier to overcome in combining with positively charged nuclei. B) Neutronization captures all the protons and electrons. C) Single protons have little repulsion to heavy nuclei and easily fuse with them. D) Photodisintegration makes many alpha particles, available for capture by nuclei. E) Neutrinos, because of their low mass and high speed, easily penetrate nuclei. 38) 39) As a star evolves, heavier elements tend to form by various processes. Which of the following is not one of these processes? A) fusion of like nuclei B) neutronization C) proton capture and neutron capture D) the s process E) helium capture 39) 40) Which type of heavy atomic nuclei are most common, and why? A) Noble gases, for they are the most stable elements. B) Even numbered elements, for helium is "giant food" for everything beyond itself. C) Metals, for iron is the last abundant element formed before the type II supernova. D) Transuranium elements, for only very heavy elements are made in supernovae. E) Odd numbered elements, because hydrogen is the building block for all heavier elements. 40) 41) The making of abundant iron nuclei is typical of A) planetary nebula ejection. B) type I supernovae. C) the helium flash. D) type II supernovae. E) all novae. 41) 6

7 42) The alpha process tends to produce chiefly A) odd numbered elements. B) stable elements. C) even numbered elements. D) only carbon. E) only radioactive elements. 42) 43) What is the reason a type-i supernova slows its dimming after about 2 months? A) Energy is released from the decay of radioactive cobalt 56 to iron 56. B) Energy from the supernova's shock wave is released as it hits interstellar matter. C) The burst of energy carried by neutrinos is finally observed. D) The planetary nebula cooled enough to form a dust shell. E) The supernova remnant suddenly becomes transparent. 43) 44) When helium capture occurs with a carbon 12 nucleus, what results? A) nitrogen 14 B) nickel 56 C) oxygen 16 D) silicon 28 E) neon 20 44) 45) The iron we commonly find in our surroundings came from A) material ejected by a nova explosion. B) decay of nickel 56 and cobalt 56 in a supernova remnant. C) the iron core of a massive star which exploded as a type I supernova. D) jets ejected by a rapidly spinning pulsar. E) planetary nebulae. 45) 46) The heaviest nuclei of all are formed A) in the ejection of matter in the planetary nebula. B) in the core collapse that set the stage of Type II supernovae. C) in the horizontal branch. D) in dense white dwarfs. E) during nova explosions. 46) 47) Which statement about our current knowledge of elements is FALSE? A) We now know of more than 110 elements, both natural and man-made. B) We have now produced over 50 radioactive elements not occurring in nature. C) Technetium is found in giant stars, but not yet in nature on the Earth. D) 10 radioactive elements are also found on Earth. E) 81 stable elements have been found on Earth. 47) 48) As seen in 1987, when two silicon 28 nuclei fuse, or when seven alpha particles are added to a Si-28 nucleus, the initial result in either case is A) a nova explosion. B) the shedding of bipolar planetary nebula shells. C) cobalt 56. D) nickel 56. E) iron ) 7

8 49) Which statement about young stars is FALSE? A) They are more likely to have planets forming with them than earlier generations. B) They contain a larger fraction of heavy elements than previous generations. C) Being young, they will have more pure hydrogen than earlier generations. D) They are born in a dustier environment than earlier generations. E) The high mass stars will be more likely to produce heavier elements as they evolve. 49) 50) Type II supernovae and star forming regions are related to one another because A) the shock waves of a supernova can trigger star formation. B) they both contain ionized hydrogen. C) as a result of both processes, lighter elements are transformed into heavier elements. D) they both involve high mass ionizing stars. E) all of the above 50) 8