PHYS/ENVI 360 Ch. 16-18 Study Guide Dr. MikulaChapter 16• Know the shape and structure of the Milky Way, including the halo, disk, spiral arms, and bulge.• Know the composition of the Milky Way, including interstellar gas and dust, as well as which stars are most common.• Know the differences between Pop I and Pop II stars.• Know the different types of star clusters and their characteristics.• Know what the zone of avoidance is and what it causes in terms of our ability to look into space.• Know the primary differences between HI and HII regions of interstellar gas.• Know the two main hypotheses for star formation in the Milky Way.• Know the basics of how we measure the Milky Way’s mass based on the orbits of stars.• Know what lives at the center of our galaxy.• Understand the 2-stage collapse model of galaxy formation, and how this explains the differ-ences in Pop I and Pop II stars.• Know what happens when two galaxies collide.Chapter 17• Know the name of the galaxy with which the Milky Way will eventually collide.• Know the types of galaxies and their characteristics, including how galaxies might transition between these forms.• Understand Hubble’s Law, what it means about the motion of galaxies, and its limitations.• Understand what causes the “red sequence” and the “blue sequence” of galaxies.• Know the characteristics of active galaxies, including the role of black holes and magnetic fields.• Know what radio galaxies, Seyfert galaxies, and quasars are.• Know what galaxy clusters are, including the name of ours and the major members.• Know what superclusters are, including filaments and voids.• Know how we use rotation curves as evidence for the existence of dark matter.• Know the two main hypotheses of what dark matter actually is.Chapter 18• Know how galaxies are distributed, how they are moving relative to each other (and what causes this motion).• Know the age of the universe and how we determine this.• Know where the “center of the universe” is.• Know what the cosmic horizon is .PHYS/ENVI 360 Ch. 16-18 Study Guide Dr. Mikula• Understand the cosmic microwave background, its origin, how the wavelengths have changed over time, how it was detected, and what the small variations became.• Know how heavier elements than hydrogen were formed in the early universe.• Know the role that anti-matter played in the early universe.• Know the curvature of our universe, and the different options for curvature.• Know what inflation is, what caused it, and how it explains the flatness and horizon problems.• Know about the past and future expansion of the universe, including the role of dark energy.Other• Know how parallax is used to measure distance to stars, as well as the limitations of this ap-proach (how far away can the stars be and still be measured this way?)• Know the name of my
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