# End of Unit 3 Assignment

This assignment consists of four parts. The first is a review with a couple of practice questions linked directly to their answers. The second is a short quiz that you take using Blackboard. It will be instantly scored for you by Blackboard; you only get one chance to take it, however, so be sure you are ready! The third part is an essay question. The question appears below; when you are ready to answer it, log on to Blackboard and submit your essay. Finally, for each unit, you should log on to Blackboard and contribute a question, an answer, or a comment to one of the posted topics. If you find the material in this unit challenging, you might want to start with the "discussion" part of the assignment in order to get some help with some of the ideas.

Brief summary of Unit Three:

In this unit we have covered the apparent daily motion of the sky that results from the rotation of the earth. We have then gone through a couple of useful concepts - equatorial coordinates, used to make a record of the position of an object on the sky independent of the position of the observer, and meridian diagrams, used to figure out how high a star or planet will get in a particular observer's sky.

Before you go to the quiz, see how you do on these two questions. If you have trouble, you might want to review the unit, send a question to the discussion group, or seek help from the instructor.

Practice Question One
A star rises five degrees north of due east. Where will it set? What can you say about the altitude of this star when it transits the meridian?

Practice Question Two
In this meridian diagram what is the observer's latitude? Is the declination of the red star positive or negative? What is the altitude of the red star on the meridian at this latitude if its declination is 15? Is the declination of the blue star positive or negative? Can the blue star be seen by an observer at latitude 75N? Explain!

When you are ready, Blackboard and take Quiz Three.

You will get instant feedback on your score on Quiz Three (and your instructor will also be informed of your score). If your score is OK, you may proceed directly to the Essay Question Two on BLackboard. Otherwise, you might want to look at what you missed, ask your instructor about questions you missed, or review relevant parts of the unit.

Essay Question

When one of the planets is very bright - like Mars in 2003 - observatories around the world get a lot of UFO reports along the lines of the following: "There was a really bright thing in the sky in the Southwest at supper time; when I went out an hour later, it had moved and two hours later it wasn't there. That must have been a UFO, right?" Explain what this observer probably saw and why it appeared to move and then disappear.