Essay Question for Exam 2
You will be asked to answer this question during Exam 2 on Thursday, March
24. Please think about how you will answer this question before the exam,
and write your answer during the exam time on the colored sheet.
PART II: ESSAY (25 points): Answer the question on this sheet only
Joni Mitchell writes that "we are stardust." She describes beautifully the
fact that matter in the Universe is continually being processed by stars and
returned to be used in future stars... and planets. Though the Universe
started out as mostly hydrogen, we are made of elements like oxygen and
carbon, and our things are made of heavier elements.
In a single essay, trace the history of hydrogen through its transformation
into heavier elements by stars. Please structure your essay as follows:
- (10 pts) Stars of low mass (like our Sun) and high mass (i.e. with
main-sequence masses in excess of 10 times the mass of our Sun) contribute
differently to the enrichment of elements heavier than hydrogen in our
galaxy.
For each mass range, name and describe the most important event in its life
that returns nuclear processed material back into space. In your answer be
sure to state the (approximate) composition of the material returned to
space, and the kind of star or stellar remnant that is left after each event.
- (15 pts) Beginning with the main sequence phase, discuss the stages in
which light elements are transformed into heavier elements.
- Where in the star does each transformation occur?
- Where is the star in the H-R diagram during each transformation?
- To what elements does a 1 Msun star take these transformations?
- To what elements does a 10 Msun star take them?
If it will help, include a sketch in your answer.