Astronomy 102, Fall 2004
Homework Assignment #1
This homework set is due at the beginning of class on Friday, September 3. It must be turned in by 9:10AM that day. Late homework will not be accepted. This is includes your being late to class.
The first three problems are required. The remaining problems are optional, and will not be graded; they are here as additional review problems for you. After the homework has been graded, solutions will be posted to all problems.
Please write out the problem statement at the top of your solution. (This is for two reasons; it is so I can know which problems you answered, and that you answered the right problem from the bit. It also will make your graded homework more useful as a study aid later.)
You may consult with other students (as well as with the TAs and professor) on this homework set. However, your final answer should be your own. Do not write down an answer you don't understand, and do not "dictate" an answer to somebody else.
You are in Nashville, facing south. You watch a star as it rises and sets; all of this takes only two hours. Draw two pictures, as follows. (a) Draw the southern horizon, and the path that you see this star take as it rises, crosses the sky, and sets. (b) Draw the celestial sphere, with the Earth at the center and you standing on it. Draw the circle that represents where this star is as the celestial sphere rotates. Indicate the portion of that circle that corresponds to the two hours between rising and setting described above.
Chapter 4, Question 12 in Pasachoff & Filippenko (p. 75).
You wake up one night, and find that you are on a desert island with no idea how you got here. After briefly vowing never to repeat the previous evening's activities, you decide to try and figure out where you are. With nothing but sea around you and the star-filled sky above, you resort to the knowledge you learned in Astronomy 102.
In one direction, you see that as the stars rise, they appear to be moving, from your perspective, up and to the left. Which direction are you looking, and what can you conclude about your location on the Earth from this observation? Explain.
The problems below are optional; they need not be turned in, and they will not be graded.
Chapter 4, Question 8 in Pasachoff & Filippenko (p. 75).
Where on Earth would you need to be in order to be able to see every star over the course of a year without changing your location? Explain.
Assume that stars are distributed evenly across the celestial sphere. (This assumption isn't quite right, but assume it to be for this problem.) What fraction of the stars would an observer at the North Pole be able to observe over the course of the year?
(Harder.) Nashville, TN is at a latitude of +36°. Under the assumption from the previous problem, what fractio of the stars would an observer in Nashville be able to observe over the course of the year? Would she be able to observe them all on the same night? Why or why not?