Physics Exam (Chapter 9)


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Side ASide B
What is the composition of the interstellar medium
about 75% hydrogen, 25% helium, 1% interstellar dust, with traces of heavier elements
How is a nebula different from the interstellar medium
A nebula can be seen with visible light
Why are these clouds of interstellar media stable
Gas pressure outward balances gravity inward. Turbulence and magnetic elds also help gas...
What is the source of energy in a protostar
Gravitational potential energy is transformed into heat as the protostar contracts
What forces are in balance in a star on the main sequence
Gas pressure outward balances gravity inward
What factors do gas pressure and gravity depend on
Gas pressure depends on temperature, which in turn, depends on the rate of nuclear fusion...
What are the characteristics of a main sequence star
(a) It's the earliest stage of a star's life. (b) It is still contracting and heating...
What is the proton-proton chain? What type of nuclear reaction is it
4 protons fuse together to form helium and energy. Nuclear fusion
What is the difference between the proton-proton chain and nuclear fission
The proton-proton chain takes the smaller hydrogen nuclei and fuses them together to form...
Where does the energy come from in the proton-proton chain
The mass of a helium nucleus is smaller than the masses of the hydrogen nuclei that are fused...
What is the CNO cycle
The CNO cycle is a nuclear fusion cycle involving carbon, nitrogen, and oxygen. It is a...
Why does the CNO cycle require a higher temperature than the proton-proton chain
There are more protons in the carbon, nitrogen, and oxygen nuclei than in hydrogen nuclei...
State the mass-luminosity relation
The more massive a star is, the more luminous it is because more mass leads to more gravity....

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