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Astronomy Week 6-9 Quiz.docx

Ignites hydrogen fusion in its core and achieves

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Ignites hydrogen fusion in its core and achieves thermal equilibrium d. Ignites hydrogen fusion in a shell and achieves thermal equilibrium e. Stops collapsing and achieves hydrostatic equilibrium Answer: C 12. A pre-main sequence star is in _____ but not yet in ____. a. Hydrostatic equilibrium, nuclear statistical equilibrium b. Mass growth, hydrostatic equilibrium c. Thermal equilibrium, hydrostatic equilibrium
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d. Hydrostatic equilibrium, thermal equilibrium e. Deuterium fusion phase, hydrogen fusion phase  Answer: D 13. The protostar phase of star formation ends and it becomes a pre-main sequence star when a. It stops growing in mass and achieves hydrostatic equilibrium b. It ignites hydrogen fusion in its core and achieves thermal equilibrium c. It becomes opaque to light and achieves hydrostatic equilibrium d. It stops collapsing and achieves thermal equilibrium e. It ignites deuterium (heavy hydrogen) fusion in its core Answer: A 14. If a hot gas rises faster than it can radiate its heat away, it becomes a. Explosive b. Unstable and convective c. Conductive  d. Stable and radiative Answer: B 15. Which of the following types of stars on the H-R diagram have a strong Mass- Luminosity relationship? (check all that apply) a. White dwarfs b. Giant stars c. Main sequence stars  d. Supergiant stars e. Subgiant stars Answer: B 16. The minimum mass of a main-sequence star is defined by  a. The mass below which the core never gets hot enough to ignite hydrogen fusion b. The mass below which the star never achieves hydrostatic equilibrium c. The mass below which the core never gets hot enough to ignite deuterium fusion d. The mass of the lowest mass clump that fragments out of a molecular cloud
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Answer: A 17. The duration of the pre-main sequence phase of star formation is set by  a. The rate of mass growth during the pre-main sequence phase  b. The thermal timescale of the star c. The Kelvin-Helmholz gravitational contraction timescale  d. The nuclear fusion timescale Answer: C 18. The CNO Cycle uses ____ as a catalyst to fuse ____ into ____ a. Carbon, oxygen, nitrogen b. Carbon, helium, oxygen c. Carbon, hydrogen, nitrogen d. Carbon, hydrogen, helium e. Carbon, nitrogen, oxygen Answer: D Week 9 Quiz: 1. What stops the collapse of the iron/nickel core in a very massive star? a. The strong nuclear force becomes important at very high density b. Fusion of elements heavier than iron generates intense gas pressure  c. Neutron degeneracy pressure becomes important at high density d. Electron degeneracy pressure becomes important at high density Answer: A 2. At the onset of collapse of the inert iron/nickel core inside a very massive star, what  energy consuming processes become important? Select all that apply a. Explosive oxygen fusion b. Neutronization c. Heavy-element fusion of iron into gold and silver
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d.
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  • Fall '18
  • hydrostatic equilibrium

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