Pad * 84% - 8:05 PM instructure-uploads,s3.amazonaws.com 120 Star Formation and

Question

Pad * 84% - 8:05 PM instructure-uploads,s3.amazonaws.com 120 Star Formation and Lifetimes 5) Based on your answer to Question 4, do you think that the rate of nuclear fusion in a high-mass star is greater than, less than, or equal to the rate of nuclear fusion in a low-mass star? 6) Which of the following statements best describes how the lifetimes compare between Star A (a star with a mass equal to the Sun) and Star B (a star with six times the mass of the Sun)? Circle the best possible response given below. (Note: It may be helpful to examine the information given in the table on the previous page.) a) Star A will live less than 1/6th as long as Star B b) Star A will live 1/6th as long as Star B c) Star A will have the same lifetime as Star B d) Star A will live six times longer than Star B e) Star A wil lve more than six times longer than Star B Explain your reasoning for the choice you made 7) The Sun has a lifetime of approximately 10 billion years. If you could determine the rate of nuclear fusion for a star with twice the mass of the Sun, which of the following would best describe how its fusion rate would compare to the Sun? Circle the best possible response to complete the sentence given below. (Note: It may be helpful to examine the information given in the table on the previous page.) A star with twice the mass of the Sun would have a rate of nuclear fusion that is the rate of fusion in the Sun a) less than b) a little more than c) twice d) more than twice Explain your reasoning for the choice you made © 2013 Pearson Education, Inc. LECTURE-TUTORIALS FOR INTRODUCTORY ASTRONOMY HIRDEDITION

Explanation / Answer

7) Nuclear reactions are generally very temperature sensitive. So, if there is a slight increase in pressure and temperature, it leads to large increases in the rate of nuclear burning, i.e., the rate of nuclear fusion. So, if there is addition of mass by small amount, the rate of nuclear fusion will increase greatly.

So, a star

with twice the mass of the sun would have a rate of nuclear fusion that is d) more than twice the rate of fusion in the Sun.

Now take a look on Luminosity of a star. Luminosity of a star stands for the amount of energy emited by it. That is, it is proportional to the rate of nuclear fusion. And there is a relation between mass and luminosity, which is, luminosity is propotional to the mass4.

I also add answer of question 6.

6) e) Star A will live more than 6 times longer than the Sun.

Star B having the mass greater than 6 times than star A.

Lifetime = mass / luminosity, luminosity = mass4 . So, Lifetime = (mass)-3.

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