PES 106 – General Astronomy II – Exam #3 Study Guide
The Milky Way Galaxy; Galaxies
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Galaxies Overview
What are the 3 fundamental astronomic structures?
What are the basic structural elements of our galaxy?
What are two theories of galactic formation?
How are distance and age related to each other?
About how old do we think our galaxy is?
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The Milky Way Galaxy
What does the Greek “galactos” mean?
How did H. Shapley estimate the size of our galaxy?
Where is Sol located within our galaxy?
What are the approximate dimensions of our galaxy (in kilo-parsecs)?
Why do we suspect that there is unseen matter in our galaxy?
How fast are we moving relative to the center of our galaxy?
How is the density of the Milky Way similar to the density in our solar system? How does it differ?
What is the average mass of a star in our galaxy?
About how many stars are in our galaxy?
What distinguishes Population I and II stars?
Where are Pop. I and Pop. II stars generally found in our galaxy?
What would we expect the characteristics of a Pop. III to be?
What are the types of star groups called?
What characterizes an association?
What characterizes an open cluster?
What characterizes a globular cluster?
About what percentage of interstellar matter is gas (as opposed to dust)?
What are the dominant gases found in interstellar matter?
Where does the dust come from?
What effects from this dust on visible light can we observe?
What is the zone of avoidance?
What is a dark nebula? What is a reflection nebula?
What is an emission nebula, or HII region?
In what ways can we observe interstellar gas?
Spiral arms of galaxies are made of what?
What are the two models of spiral arm formation?
How are galactic mass and rotation speed (tightness of the wind of the spiral) related?
What types of stars within globular clusters are used to measure galactic size?
What relatively stationary objects can we use to measure Sol’s absolute speed?
X-ray, IR, radio emissions from the very center of the galaxy indicate what lies there?
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PES 106 – General Astronomy II – Exam #3 Study Guide
The Milky Way Galaxy; Galaxies
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Galaxies
What are the two major catalogs used to organize and name galaxies?
What are the three main types of galactic shapes?
What are the two sub-types of spiral galaxies?
Elliptical galaxies are composed primarily of which Population type of stars?
Spiral galaxies are composed primarily of which Population type of stars?
Which types of galaxies have the most dust and gas, and are therefore most likely the youngest?
Far-away (old) galaxies are typically smaller than modern galaxies.
What is a likely explanation of the formation of large galaxies like the Milky Way?
What is galactic cannibalism?
What is a “star burst galaxy”?
How are distances to galaxies measured?
What are some “standard candles” used for distance measurements to galaxies?
More distant galaxies tend to have a greater redshift to their spectra.
What is a gravitational lens?
What are the three types of active galaxies?
What characterizes a radio galaxy?
What characterizes a Seyfert galaxy?
What characterizes a quasar?
What characterizes a poor cluster of galaxies?
What characterizes a rich cluster of galaxies?
Unusually fast relative speed of galaxies to each other indicates the presence of what type of unseen
intergalactic matter (probably in a halo around galaxies)?
What are some examples of groups of galactic super-clusters?
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