Physics 110: Homework Questions

(Handout #2)

Homework #3 Due 11 Feb Deadline 15 Feb

3.1

The temperature of the Sun varies from about 15 million K at the center to 6000 K at the surface. Obviously these different temperatures result in very different conditions for the center, compared to the surface of the Sun. Discuss what effect the different temperatures and conditions of these two regions have on the observed properties of the Sun.

3.2

Discuss the roles of convection and radiation in the transport of energy through the interior of the Sun.

3.3

Why is the study of solar neutrinos important? Give two reasons.

3.4

Astronomers believe that stars form in dense cores of molecular clouds. What techniques do they use to study these regions? During the evolution of a protostar, at a certain point it becomes opaque to infrared radiation. Why does this happen and why is it important?

3.5

Contrast the roles of gravity and angular momentum in the formation of stars. How would the process of star formation be different if (a) gravity were turned off or (b) angular momentum were absent?

Homework #4 Due 18 Feb Deadline 22 Feb

4.1

What do astronomers mean when they talk about the birthline for stars? Are stars like the Sun generally brighter or fainter before they reach the main sequence? Explain why.

4.2

Why is mass loss an important process in star formation? Discuss the role of circumstellar disks in constraining the mass outflow from winds.

4.3

If bipolar jets were being ejected by a young star at a speed of 200 km/s, how long would it take for the star to produce jets that are 5 parsecs long? Suppose these same jets carry away mass at a rate of kg/s. How long would it take for the young star to shed a mass equal to that of the Sun?

4.4

Describe three specific ways in which stars can generate energy. Do your three methods work for stars of all mass ranges? Explain.

4.5

Give estimates of what the Sun's luminosity, surface temperature, and spectral type were when it was years old and when it was years old.

• About this document ...