Astronomy 101 Final Exam -- Summer 1993

	There are 16 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 
16 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)  Use words and a diagram to show how the position of the North Celestial 
    Pole changes with your latitude.  At a latitude of 60 degrees North, 
    sketch briefly (just a few lines will do) the lines of sight to the 
    North Celestial Pole and Celestial Equator, giving angles of each line 
    from the horizon.

2)  Use a diagram to help explain why the maximum altitude of the Sun on the 
    date of the equinox is higher the closer you are to the Earth's 
    equator.  How does this affect shadows (i.e. what happens to your 
    shadow the closer you are to the equator)?

3)  Sketch a rough graph of the continuous spectrum (intensity plotted vs. 
    wavelength) for a blue star and a red star.  Note on your graph where 
    the visible region of the spectrum lies.  Why do some intrinsically 
    blue stars appear red when viewed through the interstellar medium?

4)  What was the source of the water on Mars (as well as the other inner 
    planets)?  Describe the process by which Mars went from a state of 
    having lots of water (much like the Earth) to having almost none 
    today.  The chief component of the Martian atmosphere today is Carbon 
    Dioxide.  Why is this still around in the atmosphere whereas the water 
    is not?

5)  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.

6)  What evidence do we have that other stars might have already formed (or 
    are currently forming) companion planets?  State what the actual 
    evidence is and why that evidence indicates the presence of planets.

7)  Use the principle of Hydrostatic Equilibrium to explain why the 
    temperature of the Sun decreases as you move within the Sun further 
    from the core.  Why is this trend reversed in the corona?

8)  Describe the physical processes that result in the upper and lower 
    limits to main sequence stellar masses (not stellar remnants, like 
    white dwarfs, etc).

9)  Why do stellar cores have to get hotter in order to fuse heavier 
    elements?  Where do the cores get the extra heat energy they need in 
    order to start fusing Helium, and what happens to the star once Helium 
    fusion starts?

10)  Where is most of the gas and dust in a spiral galaxy found?  Why does 
     this tend to make that part of the galaxy much brighter than 
     everything else?

11)  Why do spiral galaxies tend to have younger stars?  Which type of 
     galaxy (spiral or elliptical) appears bluer, and why do young stars 
     have anything to do with this? 

12)  Use dimensional analysis to show how we can find the age of the 
     Universe simply by knowing how fast something is moving away from us 
     (in km/sec) and how far that thing is away from us (in km).  How does 
     Hubble's constant relate to the age of the Universe?

13)  What does each of the following four basic observations of cosmology 
     tell us about the Universe?  
	The Copernican Principle:
	Hubble's Law:
	Olbers' Paradox:
	Cosmic Background Radiation:

14)  The Cosmic Background Explorer (COBE) discovered small fluctuations in 
     the microwave background radiation.  Why was this such a big discovery 
     (what did it explain)?

15)  Suppose the visible matter in the Universe makes up 1% of the mass 
     necessary for us to have the "critical density."  How does the 
     question of the existence of dark matter affect whether the Universe 
     is "open," "flat" or "closed?"  Also, why do most cosmologists favor a 
     "flat" Universe?

16)  What two reasons prevented all the Hydrogen in the Universe from being 
     fused into Helium during the first three minutes?  How has the 
     composition of the Universe changed since then (not numbers, just 
     trends)?