Astronomy 101 -- Study questions for the final exam

	- This list includes many questions from the mid-term study sheet
	- as well as new ones from the second half of the course.

	- You'll need to bring only a pencil to the mid-term on Thursday,
	- August 19.

	- These study questions are intended to cover everything that we
	- have covered in the course.  If you know the answers to them well,
	- then you should have no problem at all with the exam, which will
	- be entirely short answer format.

*** Questions from the first half ***

Why can't science ever give us absolutely certain knowledge about the world?

How does the position in the sky of the North Celestial Pole change
  with your latitude?  Be able to explain with a diagram.

What is the difference between the sidereal day and the solar day?  Be
  able to draw a diagram explaining this.

Draw a diagram depicting the four major phases of the Moon (the positions
  of the Earth, Moon and Sun included with labels).

Draw a diagram explaining why the Moon appears to pass very close to all
  of the planets in the sky during its orbit.

Draw a diagram explaining why eclipses don't occur at every new moon.

Know the difference between lunar and solar eclipses (diagrams again).

On what days of the year does the Sun's path in the sky during the day
  seem to follow the Celestial Equator?  Be able to explain with a diagram.

Explain why the maximum altitude of the Sun (see hw #2) on, say, the
  summer solstice, is different for different latitudes.

Be able to explain why shadows are shorter and days are longer in 
  the summer months with...that's right!...a diagram!

I hate to ask you to memorize things, but this is pretty major, so:  Be
  sure you know Kepler's three laws of planetary motion (not the full-blown
  descriptions...just a brief phrase explaining each).

What is it about gravity that causes tides?  Also, be sure you know how
  the strength of gravity varies with distance.

Know how wavelength, frequency and Energy of light are related.

How can we tell from looking at a spectrum with four or five absorption
  lines in it what atoms are in the absorbing material?

How can we know what the temperature of a star is just by knowing
  how many (what fraction) of the atoms are excited or ionized?

What is the difference between an absorption and emission and continuous
  spectrum?  What kind of set-up do you need to have to see each type?

Be able to sketch a rough graph of the continuous spectrum (intensity
  plotted vs. wavelength) for a very hot and relatively cool body.

How does the Doppler shift cause redshifting or blueshifting?  How can
  we use this to determine velocities of things? 

Why are the densest planets the closest to the Sun?

Describe the current best theory that explains the origin of Earth's Moon.
  How does this theory explain why the Moon is not "dense enough"?  What
  other evidence leads us to believe this theory is right?

What is some of the evidence that leads us to believe a giant cometary
  or asteroid impact resulted in the extinction of the dinosaurs?

The Earth and Venus started off with roughly the same atmospheric composition,
  but Venus is radically different from the Earth.  Describe the 
  process that led to the current conditions on Venus.  What is one 
  piece of evidence that helps confirm this theory?

Mars also started out with an atmosphere with composition similar to
  the Earth's.  What do we think happened to the water?  What about the
  other light elements?  What is left of the Martian atmosphere?

Why are the Jovians so big?

Why can't we directly image (or see) planets like Jupiter orbiting other stars?

What would be the most noticeable effect a Jupiter-sized planet would
  have on the star it is orbiting (the effect we would be most likely to see)?

What evidence do we have that other stars might have already formed (or
  are currently forming) companion planets?

*** Questions from the second half ***

Describe how the process of hydrostatic equilibrium keeps stars stable
  over the course of their lifetimes.

Where does the Sun's energy come from?  How does this energy get out of
  the core of the star, and how does it change in the process of leaving
  the star (what is the final form)?

What does nuclear energy generation only occur in the central regions of
  stars?  How does this serve to limit the main sequence lifetime (Hydrogen
  burning lifetime) of a star?

What is the definition of a black hole?  Where is the boundary defined to be?

Why is the corona so hot?

Why do massive stars have shorter lifetimes than less massive stars?  Be
  sure to mention _what_ causes the shorter lifetimes as well as _why_
  this happens in stars.

Why are there upper and lower limits to stellar masses?

Why do stellar cores have to get hotter and hotter to fuse heavier elements?

Sketch the process of a supernova, starting with the onset of iron fusion
  in the core of the star.  What is the structure of the star at this time?

How do we know that virtually all the Uranium in the Universe came from
  supernovae?

Draw a diagram explaining how we see neutron stars appear to "pulse."

Draw a diagram showing how we use parallax to determine the distance to
  other nearby stars.  Why doesn't this work for more distant objects?

Use a graph to show why stars have different colors depending on their
  temperatures.

Why is the sky blue and the sun red at sunset?

Where is most of the gas and dust in the disk of the galaxy found, and why
  does this tend to make that part of the disk unusually bright?

What is it about the rotation pattern of the galaxy that leads us to 
  believe dark matter exists beyond the visible edge?  Use a graph to help.

How has the interstellar medium change over time?  How do we know what
  the initial composition was?

Why are elliptical galaxies redder (i.e. what is it about their histories
  that make them appear redder today) than spirals?

How do we know that quasars are extremely (intrinsically) bright?

What is Hubble's Law, and how can we determine the age of the Universe
  from Hubble's constant (use dimensional analysis)?

Why is the night sky dark?

Know each of the four basic observations of cosmology and what each tells
  us about the Universe:
	- The Copernican Principle (i.e. tells us U is homogeneous & isotropic)
	- Hubble's Law
	- Olbers' Paradox
	- Cosmic Background Radiation

How did the Cosmic Background Radiation originate, and why is it sometimes
  called the Microwave Background (use a graph to demonstrate)?

Give a rough chronology of what happened in the early Universe.  I won't ask
  you to know times, but I will want you to know the order of events.

What is so great about the fact that the Cosmic Background Explorer (COBE)
  measured small variations in the background radiation?

If the Universe had an edge, what principle would this violate and why?

How does the overall density of the Universe determine whether it is "open"
  or "closed?"  What is the critical density?

If the density of the Universe today is greater than the critical density,
  what do we think will happen to the Universe eventually?

Why is dark matter so crucial in determining the density of the Universe?

Why didn't all the Hydrogen in the Universe get fused into Helium or even
  heavier elements during the era of nucleosynthesis (two reasons)?

Why is the theory of inflation taken seriously?

In order to look for possible signals from Extra-Terrestrial Intelligence,
  what part of the spectrum do we observe and why?