Astronomy 123
Test 1, 22 October, 2010
Fall 2010
NAME ______________________________________________
There are five (5) equally-weighted multipart questions.
Each question is worth 10 points.
Question 1:
(2 points) a) State the Cosmological Principle,
the Perfect Cosmological Principle,
and the Anthropic Principle.
(2 points) b) Define homogeneity and isotropy. Include a sketch
to illustrate your
explanation.
(6 points) c) Explain how Einstein's consideration of the
Perfect Cosmological Principle
led to the suggestion of a universal repulsive force included in
his model for the Universe as the Cosmological Constant. What caused
Einstein to withdraw his suggestion of a Cosmological Constant?
Question 2:
(2 points) a) In essence, give the basic ideas of the
Big Bang Theory.
(3 points) b) Cite the observations upon which the
Big Bang Theory is based.
(5 points) c) Is the Big Bang Theory considered to be on
secure ground by
cosmologists? Explain why it is of is not considered to be on firm ground.
In particular, point out the reasons why the evidence which supports
the Big Bang
cited in b) offer strong support for the Big Bang theory or why they
do not offer strong support for the Big Bang theory.
Question 3:
(2 points) a) What is a black hole? When was the concept
of a black hole first developed?
(2 points) b) Describe a nonrotating black hole, a
Schwarzschild black hole. Be sure to define the Event Horizon,
singularity, and Schwarzschild Radius
in your description.
(2 points) c) State the Cosmic
Censorship theorem.
(4 points) d) What are the properties of the black hole at the center of the
Milky Way galaxy? Describe how rotating (Kerr) black holes
and nonrotating (Schwarschild) black holes can act as energy engines.
Question 4:
(2 points) a) What is meant by the term Dark Matter?
(6 points) b) Describe two results which indicated the presence of
Dark Matter.
(2 points) c) Roughly, what fraction of the Universe is
Dark Matter? What fraction
of the matter in the Universe is Dark Matter?
Question 5:
(5 points) a) Sketch the Hubble Tuning Fork diagram.
Describe how the general properties
of galaxies vary along the Hubble Tuning Fork diagram
(consider gas and dust, stellar populations,
Pop I and Pop II stars, star formation, flattening, bulges,
and winding of spiral arms).
(2 points) b) Did Hubble consider his Tuning Fork diagram to
represent a galactic evolutionary
sequence? Is it currently believed to be an evolutionary sequence?
(3 points) c) What are the results of collisions
between similar mass disk galaxies, between
galaxies of greatly differing masses?
Are collisions between galaxies likely to be rare
occrences? Present an argument which supports your
answer concering the probability of galaxy collisions.