Gets brighter in luminosity and grows slowly in

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Gets brighter in luminosity and grows slowly in radius  d. It loses half or more of its mass as hydrogen is fused into helium e. Grows slowly in radius at nearly constant luminosity  Answer: E 11. In massive stars, why is each successive core nuclear fusion phase shorter and  shorter? a. The stars luminosity gets less as it ages, reducing the nuclear energy needs b. There is an increasingly smaller mass of nuclear fuel at each stage c. Each successive nuclear fusion stage runs cooler and cooler, generating less energy d. Fusion of increasingly heavier nuclei is increasingly inefficient at generating energy Answer: D 12. What becomes of the heavy-element enriched gas in the envelopes ejected from  massives stars by core-collapse supernovae? a. Hydrogen and helium mix with interstellar gas, but the heavy metals fall back on the core b. It blows huge bubble of vacuum, destroying heavy metal as it goes c. The gas heats and mixes with interstellar gas, but does not change its heavy metal content d. The gas heats and mixes with interstellar gas, seeding it with heavy metals Answer: D 13. Why does a low-mass (less than 4 solar mass) star never ignite carbon fusion in its  core? a. The star explodes as a supernova before carbon fusion ignites  b. The inert C-O core becomes a black hole before carbon fusion ignites c. The inert C-O core never becomes hot enough to ignite carbon fusion d. It never builds up enough carbon to reach critical mass Answer: C 14. What happens if you try to fuse nuclei heavier than iron and nickel?
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a. Nuclear fusion release energy instead of taking (consuming) energy b. Nuclear fusion takes (consumes) energy instead of releasing energy c. You build up an inert gold/platinum core inside the massive star d. You extend the lifetime of a very massive star by about 1 billion years Answer: B 15. As a low-mass (less than 4 solar mass) main-sequence star ages it a. Grows slowly in radius at nearly constant luminosity  b. The amount of helium at the surface increases as fusion proceeds c. It slowly builds up an inert carbon-oxygen core d. It loses about half of its mass as hydrogen is fused into helium e. Gets brighter in luminosity and grows slowly in radius  Answer: E
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  • Fall '18
  • hydrostatic equilibrium

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