Astr 222 Final Exam Study Questions
Short Answer Questions
The final exam will list NINE short
answer questions; you must pick SEVEN of them to answer. Roughly half of the questions will
cover Cosmology and the other half will cover material from the
Milky Way and Galaxies sections of the course. The
questions below are examples from the Cosmology section of the
course; you should review the study notes for Midterms 1 and 2
for examples from earlier sections.
Each short answer should be a short paragraph or so in
length, and they will be worth 5 points each. Remember, feel free
to include a sketch in your answer if it helps you explain things.
- Describe what was was happening in the Universe at the era of
recombination.
- Sketch how the expansion factor changes with time (i.e., the
R(t) plot) for a Universe with H0=72 km/s/Mpc, OmegaM=2.0, and
OmegaL=0.0. Give two reasons we can easily rule this out as the
correct set of cosmological parameters.
- Explain why matter and dark energy work together to make the
Universe spatially flat, but work against each other to change
the expansion history of the Universe.
- Describe what we mean by hierarchical galaxy formation.
- Describe how studies of distant supernovae have helped
astronomers better understand the expansion history of the
Universe.
Essay Questions
The final exam will have TWO essay
questions; you must answer both, and they will be worth 15 points
each. One will come from the list below, which concentrates on the
Cosmology section of the course. The other will come from the
essay questions lists for Midterm 1 and Midterm 2.
Your essays should be ~ 2-3 blue book pages in length; essays much
shorter than that probably will not be giving enough detailed
explanation to get full credit.
- Describe the early history of the Universe,
starting with inflation and going through recombination.
- Describe (in detail) 3 pieces of evidence for
dark matter in the Universe (using evidence that we have
discussed in class).
- Give plausible values for the cosmological
parameters: age, H0, OmegaM, OmegaL. For each,
describe two pieces of evidence which supports the value
you've given.
- Two cosmological processes --- Big Bang
Nucleosynthesis and the formation of structure in the Universe
--- provide some of our strongest constraints on the nature of
dark matter. Describe these two processes and explain how they
demonstrate that dark matter cannot be baryonic.
- Describe the flatness and smoothness problems,
and explain how inflation fixes these problems.
- Why does large scale structure in the Universe grow
differently under different cosmological models?
Describe/explain the difference in how structure forms both
between cold and hot dark matter cosmologies, as well as in
cold dark matter cosmologies with different values for OmegaM
and OmegaL. Explain how can we constrain the value of OmegaM
using observations of large scale structure.
- Describe how the appearance of a normal spiral
galaxy would change (in terms of apparent magnitude, angular
size, surface brightness, and morphology) if we were to
magically move it to higher and higher redshift and observe it
with Hubble. You don't need to give quantitative numbers, but
describe qualitatively what is happening. How would things be
different if you did the same exercise with an elliptical
galaxy instead?
- Explain what the microwave background is and
how it formed, and explain a few reasons why it is so
important for our understanding of the Universe. Why does it
have a temperature of roughly 3K? Imagine being a cosmologist
roughly 7 billion years ago -- roughly what temperature would
you measure for the microwave background at that time? Explain
your answer.
Calculations
There will be THREE calculation
problems listed on the final; you must complete all three. Each
answer will be worth 5 points. These problems will be similar to
the ones listed below.
- You are observing a galaxy group consisting of
three galaxies. One of them is a spiral galaxy with an
apparent I-band magnitude of 12.3 and an inclination-corrected
(i.e., true) rotation speed of 220 km/s. How far away is the
group? If the other galaxies have apparent I-band magnitudes of 12.5
and 12.0, what is the luminosity (in solar luminosities) of
the brightest galaxy? What is the total luminosity of all the
galaxies combined?
- If you had a telescope that could detect
objects down to mB=22, what is the maximum distance
a galaxy could be at if you wanted to study its globular
clusters (which have a typical luminosity of LB ~
6x105 Lsun)?
- You are studying two galaxies which have both
had Type Ia supernovae in them. The supernova in Galaxy 1 had
a maximum brightness of mB=12, while the one if
Galaxy 2 had a maximum brightness of mB=15.5. How
much further is Galaxy 2 than Galaxy 1? You do not need to
know the absolute maximum magnitude of supernovae Ia to
answer this!
- Show how the Friedman equation (given on the
equation sheet) can be used to derive the mass density of a
flat universe without a cosmological constant. If H0=72
km/s/Mpc,
what
is the density?