Physics 110: Homework Questions

(Handout #4)

Homework #7 Due 25 Mar Deadline 29 Mar

7.1

Why do most visual binaries have long orbital periods (greater than a few years)? Why are there few spectroscopic binaries in which the stars are separated by more than 10 AU?

7.2

In an eclipsing binary system, star A is brighter, larger, and cooler than its companion, star B. What can be said about the depths of the minima when each of the stars is eclipsed? Would the optical spectrum of the binary system change as a function of time and, if so, how?

7.3

Suppose the less massive star (star 2) in Figure 21.14 (Fix p. 489) expands until it fills its Roche lobe. Describe what will happen as the star continues to expand.

7.4

What does mass exchange have to do with the occurrence of a type Ia supernova? Why does mass exchange result in such a different outcome for the accreting white dwarf in a nova versus a type Ia supernova?

7.5

What is the basic origin of the energy emitted by accretion disks in binary systems?

Homework #8 Due 1 Apr Deadline 5 Apr

8.1

Why are the HII regions around O stars generally larger than those around B stars? Why wouldn't you expect to detect strong 21 cm emission from an HII region?

8.2

What was the principal reason that the measurements of Herschel and Kapteyn did not reveal the correct shape and size of the Galaxy?

8.3

Why do astronomers believe that most of the mass of the Milky Way is not visible? Describe the observational evidence that supports this remarkable claim.

8.4

How have the spiral arms of the Milky Way been revealed? Give the arguments in favor of a ``wave-like'' origin for the spiral structure.

8.5

Describe the evidence that there is a massive black hole in the center of the Galaxy.

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