Astr 222 Midterm Exam 2 Study Questions
Short Answer Questions
(There will be five short answer
questions total on the midterm, worth 5 points each. They will be
similar in style to the ones below.)
- Describe the general properties of starburst
galaxies and explain how these starbursts might be triggered.
- You are studying a galaxy cluster whose
distance you have determined from its redshift, and
you calculate a
mass of 1015 Msun for it. How and why does your
Hubble constant? If the Hubble constant was actually 20%
thought, how would your answer for the mass change?
- Sketch and label what's going on in the inner
regions of an active galactic nucleus.
- Describe Cepheid stars and explain why they
important for studying galactic structure.
- Describe the evidence for a black hole at the center of
galaxy. Roughly how massive is this black hole?
- Describe how the population of galaxies in clusters
appears to have changed over time. Why might these changes
(One of the following essay
questions will be on the
midterm, and be worth 15 points.)
- Describe the Microwave Background: what it is, the physics behind it, and what it tells us about the Universe.
- Describe the unified model for quasars and
active galaxies. How does it
differences between Type I and Type II Seyferts? What
active galaxies does it not explain?
- Describe the Tully-Fisher relationship and the
Fundamental Plane. What quantities are involved, and what types
of galaxies do they describe? What do they tell us about the
mass-to-light ratio of galaxies, and how can they be used to
obtain distances to galaxies?
- Describe three ways for getting the mass of a
galaxy cluster, and what data you would need in each case. Do
these three method give reasonably consistent answers? Why or
- Write down the Friedmann equation, including
all terms. Describe qualitatively what role each term
plays in terms of the structure and evolution of the universe.
- Describe the properties of spiral arms. Explain how
density waves work, and how they solve the winding problem.
Why would star formation occur preferentially in spiral arms?
- Describe several different lines of evidence that
indicate we have a massive black hole at the center of our
- Describe how the merger of two spiral galaxies could
produce an elliptical. Think both about the shapes of galaxies
and how stars orbit inside them. Explain how a galaxy merger
could transform some of the cold gas we see in spiral galaxy
disks into the hot gas in an elliptical galaxy halo.
(There will be two calculation
problems on the exam, worth 5 points each. These are not the
problems, but they will be similar....)
- A distant galaxy cluster has a velocity
km/s and a half-light radius of 120 arcminutes. It has a
velocity of 8000 km/s. How far away is it? Use the virial
that the mass of the cluster is ~ 5Rsigma2/G.
mass of the cluster.
- If you had a telescope that could detect
mB=22, what is the maximum distance a galaxy could
be at if
you wanted to study its globular clusters (which have a
of LB ~ 6x105 Lsun)?
- Use the Friedman equation to calculate the
a flat universe without a cosmological constant. If H0=72
is the density?