Review 4
Chapters 22: The Milky way
How do we know that there is gas and dust in interstellar space? How were the size and shape of the Milky Way discovered? What is the shape, form, structure, and various parts of the Milky Way? Where is our sun located in the Milky Way? Why do astronomers think that much of the Milky Way consists of “dark matter”? Why does the galaxy have spiral arms? Is there a massive black hole at the center of the galaxy? What is an HII region and how does it evolve? What is the origin of the 21 cm line and how do we utilize it in astronomy? What are the various types of nebulae in the Milky Way?
Chapter 23:
What are the different kinds of galaxies? How have astronomers determined the distances to galaxies? What makes astronomers think that galaxies contain vast amounts of dark matter? How do we think galaxies formed? Why do nearly all galaxies have redshifted spectra? Why do the red-shifts of galaxies increase with their distances?
A galaxy is moving away from us at a speed of 30,000 km/s . How far is the galaxy away from us?
Hint: Use Hubble’s law: V=H d and take the value of H from the book and the above value for V and solve for d. Make sure that you find d in the correct units. For this you
may need to convert the units of Hubble’s constant H in the right units.
Chapter 24-25:
To what extent are galaxies found in clusters rather than in isolation? What evidence do we have that there is dark matter? How are galaxies and clusters of galaxies distributed in space? Why are there enormous voids in which there are few galaxies?
Chapters 26: What does Hubble’s law tell us about the beginning of the universe? How can we tell how old the universe is? Can space itself be curved? What does that mean? How could we tell? What important events happened early in the history of the universe? How matter was created? What is the recombination period? What is the so-called cosmic microwave background radiation (CMBR) and how it was discovered? What is the meaning of anisotropies in the angular distribution of the CMBR? What will the future of the universe be like and how the various scenarios depend on the curvature of spacetime?
Use a value for Hubble’s constant of 70 km/s/Mpc to calculate the age of the Universe assuming a constant rate of expansion.