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1.1) In a star's core the average mass number for ions which are not hydrogen or helium is 10. The mass fractions of hydrogen is 0.60, of helium is 0.38, and all other elements is 0.02. Calculate the average ion mass in units of mH. 1.2) Explain two assumptions behind the Kelvin-Helmholtz timescale. 1.3) In the outer core of a massive star the temperature is 108 K. The mean particle weight is u = 0.62. Calculate the density of this region if the radiation pressure is equal to the thermal pressure. 1.4) For temperatures around 1.5 x 10' K in a stellar core, describe why it is hydrogen instead of heavier ions which undergo fusion. Also, when the temperature is higher, describe why higher mass ions can undergo fusion. 1.5) Describe two possible causes of convective instability in the outer regions of a low mass star.

1.1) In a star's core the average mass number for ions which are not hydrogen or helium is 10. The mass fractions of hydrogen is 0.60, of helium is 0.38, and all other elements is 0.02. Calculate the average ion mass in units of mH. 1.2) Explain two assumptions behind the Kelvin-Helmholtz timescale. 1.3) In the outer core of a massive star the temperature is 108 K. The mean particle weight is u = 0.62. Calculate the density of this region if the radiation pressure is equal to the thermal pressure. 1.4) For temperatures around 1.5 x 10' K in a stellar core, describe why it is hydrogen instead of heavier ions which undergo fusion. Also, when the temperature is higher, describe why higher mass ions can undergo fusion. 1.5) Describe two possible causes of convective instability in the outer regions of a low mass star.

College Physics
College Physics
10th Edition
ISBN:9781285737027
Author:Raymond A. Serway, Chris Vuille
Publisher:Raymond A. Serway, Chris Vuille
Chapter12: The Laws Of Thermodynamics
Section: Chapter Questions
Problem 28P: Suppose the Universe is considered to be an ideal gas of hydrogen atoms expanding adiabatically. (a)...
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1.1) In a star's core the average mass number for ions which are not hydrogen or helium is 10. The mass fractions of hydrogen is 0.60, of helium is 0.38, and all other elements is 0.02. Calculate the average ion mass in units of mH. 1.2) Explain two assumptions behind the Kelvin-Helmholtz timescale. 1.3) In the outer core of a massive star the temperature is 108 K. The mean particle weight is u = 0.62. Calculate the density of this region if the radiation pressure is equal to the thermal pressure. 1.4) For temperatures around 1.5 x 10' K in a stellar core, describe why it is hydrogen instead of heavier ions which undergo fusion. Also, when the temperature is higher, describe why higher mass ions can undergo fusion. 1.5) Describe two possible causes of convective instability in the outer regions of a low mass star.
Transcribed Image Text:1.1) In a star's core the average mass number for ions which are not hydrogen or helium is 10. The mass fractions of hydrogen is 0.60, of helium is 0.38, and all other elements is 0.02. Calculate the average ion mass in units of mH. 1.2) Explain two assumptions behind the Kelvin-Helmholtz timescale. 1.3) In the outer core of a massive star the temperature is 108 K. The mean particle weight is u = 0.62. Calculate the density of this region if the radiation pressure is equal to the thermal pressure. 1.4) For temperatures around 1.5 x 10' K in a stellar core, describe why it is hydrogen instead of heavier ions which undergo fusion. Also, when the temperature is higher, describe why higher mass ions can undergo fusion. 1.5) Describe two possible causes of convective instability in the outer regions of a low mass star.
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