Astronomy 101 Mid-Term -- Summer 1993

	There are 15 questions on this exam.  You must attempt at least 12 
of these questions, presumably the 12 you feel most confident about 
answering.  If you answer more than 12, ONLY the first 12 will be 
graded.  You may write out answers to all 15 should you choose to do so, 
but only the 12 answers you indicate will be the ones that are graded 
(you may cross out answers you want ignored).

	These questions are worth 8 points apiece.  You get a free 4 points 
just for writing your name and TA name (Knut or Mark) and section on 
the exam.

	Answer all questions in the space provided.  If you need more 
paper with which to continue your answer, raise your hand and one of 
us will bring you blank paper from the front of the room.  For each 
answer, a few sentences or a well-labelled diagram should be sufficient.  
You have plenty of time to finish the test, so don't rush and please don't 
write too much.  If you write down something unnecessary to the answer 
and it is an incorrect statement, points will be deducted!

1)  Explain in words or with a diagram (or both) how the Moon creates 
    tidal bulges on both the side of the Earth facing the Moon and the 
    side of the Earth opposite the Moon.

2)  Suppose I gave you a spectroscope and asked you to look at a particular 
    glowing cloud of gas.  Show what you would see with a rough diagram 
    and state how (and why) you would be able to tell by looking at the 
    spectrum what gas is contained in the cloud.  You may assume that I 
    provide you a guide that matches elements to their unique patterns of 
    emission or absorption.

3)  How can we tell how fast an object is moving toward or away from us 
    just by measuring the shift in wavelength of a particular spectral 
    feature (like an emission line)?  How does the width of an emission 
    line relate to the temperature of an object and why?

4)  Explain why the densest planets in the solar system formed closest 
    to the Sun.

5)  What is the current most favored theory for the origin of the 
    Earth's Moon?  How does this theory explain the fact that the Moon 
    doesn't seem to have a large, dense iron core like the rest of the 
    bodies in the inner solar system?

6)  What is the evidence that leads us to believe that the mass extinction 
    of 65 million years ago (the so-called KT event that killed off most 
    dinosaurs) was caused by a giant impact?  Be sure to state what the 
    evidence is and why it points to the impact of an object that didn't 
    originate near or on Earth.

7)  Venus' atmosphere started with lots of water and Carbon Dioxide, but 
    now we find that the atmosphere is dominated by Carbon Dioxide.  State 
    where the water went and why this made the planet hotter.  Why does 
    the presence of "heavy water" (D20) in large amounts on Venus (as opposed 
    to anywhere else in the solar system, like the Earth) confirm this theory?

8)  What are two reasons that Jupiter is so much larger than Mars?  Be sure 
    to be complete in your answer and explain why each effect contributed 
    to Jupiter's large size.

9)  We have never set foot on ground outside the orbit of the Moon, yet 
    we claim to understand events that happen millions and billions of 
    light years away.  What two basic assumptions do we need to make to 
    support this wild claim?

10)  The latitude of Dushanbe, Tadzhik S. S. R. (in the former Soviet Union) 
     is 38 degrees North.  The diagram below represents the local horizon 
     at Dushanbe.  Draw in the location of the North Celestial Pole and 
     the Celestial Equator, labelling the altitude of each off of the horizon.

[diagram not included in ASCII version]

11)  The sidereal day, the time the Earth takes to rotate once with respect 
     to the fixed background of stars, is about 4 minutes shorter than 
     the solar day.  What do we mean by a "solar day" and why is it longer 
     than the sidereal day?  Draw a diagram and give a brief explanation.

12)  Why does the angular size of the Moon (not just the lit part) change 
     over the course of a month?  Draw a bird's eye view of the Moon's 
     orbit, and label points where the angular size is smallest and largest.  

13)  Explain with a few sentences or a diagram why there are not lunar 
     eclipses every month.  Also, show or state what conditions are necessary 
     in order to produce a lunar eclipse.

14)  What is the declination of the Sun on the vernal equinox?  At what 
     latitude on the Earth would the Sun be directly overhead on the 
     vernal equinox?

15)  Look at the following two sketches of the view of the sky from the 
     cities of Wellington and Bujumbura.  Labelled on the sketches are the 
     paths of the Sun on June 22, March 21 and December 22.  Also labelled 
     are the positions of the North and South Celestial Poles.  Which 
     city lies further North and why?

[diagram not included in ASCII version]