Astro 201 Exercise 2 - questions and answers


Questions

  1. Why can't an Australian use the big dipper to find the north direction?
  2. What is the relationship between the equator and poles of the celestial sphere and the equator and poles of the earth?
  3. Where on earth do you have to be in order for the north celestial pole to be (a.) on the horizon? (b.) overhead? (c.) beneath your feet?
  4. Around September 22 the sun is at the equinox. Where should you stand on earth to see the sun directly overhead at noon?
  5. On Sept 22 at the north pole, where to you look to see the sun?
  6. At the north pole, what is the maximum altitude (in degrees above the horizon) that the sun can reach? About what day of the year does this happen?

Answers

  1. Australia is in the southern hemisphere, around the curve of the earth where north polar stars disappear from view. Not to worry, Australians can see the Magellanic clouds and other wonders that we cannot.
  2. The celestial equator and poles are extensions of the earth's equator and poles onto an enormous imaginary sphere centered on earth (the celestial sphere).
  3. (a.) At the equator. (b.) At the north pole. (c.) At the south pole.
  4. At the equinox, the sun is on the celestial equator (the extension of earth's equator into space) so the sun passes overhead if you are standing on the equator.
  5. The sun straddles the horizon. At the north pole, the celestial equator and the horizon are the same thing.
  6. Around June 22, the sun reaches 23.5 degrees above the horizon.
Last modified: Tue Sep 1 21:47:00 CDT 1998