Exam 12: Star Stuff

You discover a binary star system in which one member is a15 solar mass main-sequence star and the other star is a 10 solar mass giant star. How do we believe that a star system such as this might have come to exist?

What happens when a main-sequence star exhausts its core hydrogen fuel supply?

Falsifying Scientific Theories: In many simple expositions of the scientific method, it is often stated that if a scientific theory makes an incorrect prediction, it is falsified and must be discarded. Argue against this simple view of the scientific method by using the Algol paradox (Section 12.4) as a case study. In particular, why did astronomers not discard the theory of stellar evolution despite an apparent direct contradiction of a fundamental prediction of stellar evolution, that more massive stars evolve faster than less massive stars?

Choose from the list below for the following questions. You may use a choice more than once. -Which method of energy generation provides the source of energy for a 10Msᵤn main-sequence star?

This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with roman numerals. During which stage is the star's energy supplied by primarily by gravitational contraction?

Consider the star to which the arrow points. How is it currently generating energy?

Angular momentum plays an important role in star formation. Which of the following characteristics of a protostellar system is probably not strongly affected by the star's angular momentum?

Consider the star to which the arrow points. Which of the following statements about this star is not true?

During which of the following phases of life is a star's pressure and gravity out of equilibrium?

The main source of energy for a star as it grows in size to become a red giant is ________.

This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with roman numerals. What will happen to the star after stage viii?

What percentage of a star's total lifetime is spent on the main sequence?

Stellar Evolution as a Scientific Theory: Based on the chapter material, list what you feel are the basic founding assumptions of the theory of stellar evolution. For example, you might list that stars are assumed to be balls of mostly hydrogen gas held together by their own gravity. After this, make another list of as many of the successful predictions of this theory as you can. Based on the comparison of these two lists, how successful a scientific theory would you rate the theory of stellar evolution?

What did Carl Sagan mean when he said that we are all "star stuff"?

Why don't low-mass stars have the CNO cycle occurring in their cores?

Stars spend about 90% of their lifetime on the main sequence

When does a star become a main-sequence star?