2009 Midterm 2 Q & A.pdf

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ANTH 122
Judith Mclean

1. Why does the stellar nuclear fusion process stop with iron? (a) Because the core of heavy-mass star never reaches high enough temperature for iron fusion (b) Because iron is not a part of the CNO cycle (c) Because the core pressure of heavy-mass star never becomes high enough for iron fusion (d) Because most of the heavy mass star is still made of hydrogen (e) Because it has the lowest mass per nuclear particle Answer (e) 2. Which one of the following is the right ordering of the Sun’s interior layers coming from the inside out? (a) core, radiation zone, convection zone, photosphere (b) photosphere, radiation zone, convection zone, core (c) radiation zone, photosphere, convection zone, core (d) core, convection zone, radiation zone, photosphere (e) core, photosphere, convection zone, radiation zone Answer (a) 3. Which of these groups of particles has the greatest mass? (a) a helium nucleus with two protons and two neutrons (b) four electrons (c) four individual protons (d) two protons and two electrons (e) two neutrinos Answer (c) 1 III II IV I V 4. Consider the above Hertzsprung-Russell diagram. Which of the following is true? Each circle represents a star in that region. (a) I has the largest radius (b) II is the most luminous star (c) III has the smallest radius (d) IV is a main sequence star (e) V is a brown dwarf Answer (d) 5. What is the smallest mass a newborn star can have? (a) 8.00 ⇥ M sun (b) 0.8 ⇥ M sun (c) 0.08 ⇥ M sun (d) 0.008 ⇥ M sun (e) 0.0008 ⇥ M sun Answer (c) 6. Which one of the following does not belong in the life and death of a high-mass star? (a) Red super giant (b) Hydrogen shell burning (c) Helium shell burning (d) Carbon shell burning (e) Planetary nebula Answer (e) Planetary nebula is for low mass star. 2 7. Which of the following is the right description of the main sequence stars? (a) Stars on the main sequence are all fusing hydrogen into helium in their cores. (b) Stars on the main sequence are all fusing helium into carbon in their cores. (c) Stars on the main sequence are all fusing carbon into iron in their cores. (d) The mass of a star on the main sequence has nothing to do with its position in the Hertzsprung-Russell diagram. (e) Heavier main sequence stars have lower temperature than the lighter ones. Answer (a) 8. What do we need to measure in order to determine a star’s luminosity? (a) apparent brightness and mass (b) apparent brightness and temperature (c) apparent brightness and distance (d) apparent brightness and pressure (e) apparent brightness and magnetic force Answer (c) 9. Where do stars form? (a) In cold, relatively dense molecular clouds (b) In binary systems where mass exchanges occur (c) Inside planetary nebulae (d) In the regions of space where magnetic field is very strong (e) None of the above Answer (a) In the textbook, Summary 16.1, “Stars fom in cold, relatively dense molecular clouds.” 10. Why does the contracting molecular cloud heat up? (a) As it contracts, nuclear fusion process begins right away. (b) As it contracts, carbon and oxygen contained in the cloud becomes carbon- dioxide, releasing chemical energy (c) As it contracts, carbon monoxide becomes more abundant which radiates away more energy from the cloud (d) As it contracts, gravitational energy of the original cloud becomes heat energy (e) As it contracts, the photons that were contained in the original cloud
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