ISP 205, Section 3, Spring 1997

Quiz #2

Tuesday, March 25, 1997

						    Name: ________________________



						    Student Number: ______________
1. (10 points) Choose a star from the accompanying HR diagram and write down its name. Sketch its internal structure. Show where energy is being generated (and write down the process). Label the regions of different composition with their primary element(s).

If you selected the easiest star, the Sun, a simple version of Figure 16-12 was satisfactory, or the diagram from the Outline.
The composition information, hydrogen and helium in the core and a hydrogen envelope, needed to be added.
Also, the process of nuclear fusion is H->He in the core.
Using the made-up word "fussion" is unacceptable, as we don't know if you mean fission or fusion. These are different processes!

In the future, the simpler stellar structure sketches in Chapters 18 rather than Figure 16-12 will be sufficient.

Since we permitted you to select a red giant, and some students did, this question was beyond the advertised range of the quiz, Chapters 11-16. Therefore, we are making the entire quiz worth only 34+34=68 points. Any student who scored more than 34 points gets extra credit for those additional points.

2. (6 points) Look at the locations of Aldebaran, Antares, Procyon and Vega in the accompanying HR diagram. Which one typically emits the highest energy photons?

(a) Aldebaran
(b) Antares
(c) Procyon
(d) Vega
 (e) There is not enough information to decide.

This is based on being able to read an HRD, combined with knowing Wien's Law.

3. (9 points) Apply the balance conditions that determine the structure of a star to explain what would happen if the rate of nuclear reactions in the core of a star were to increase. Circle the correct choice in each triplet in the paragraph below.

If the rate of nuclear reactions in the core of a star were to increase, then the temperature in the core would (decrease) (remain unchanged) (increase). As a result the pressure in the core would (decrease) (remain unchanged) (increase). Then the pressure will be (less than) (the same as) (greater than) the gravity. So the core of the star will (contract) (not change) (expand). As a result the temperature in the core will (decrease) (remain unchanged) (increase), and also the insulating ability of the star will (decrease) (remain unchanged) (increase). The first of these effects will make the rate of energy generation in the core (decrease) (remain unchanged) (increase) as well as make the presure in the core (decrease) (remain unchanged) (increase), and the second of these effects will make the luminosity of the star (decrease) (remain unchanged) (increase). As a result, the star will come into balance again.

4. (8 points) The direct method of detemining the masses of stars (other than the Sun) is to apply Kepler's 3rd Law to systems of binary or dual stars.

5. (6 points) Which of the following is NOT a test of models of stars?

(a) Comparing observations of neutrinos from the Sun with prediction of Solar models.
(b) Comparing observations of planets around other stars with predictions of stellar models.
 (c) Comparing the observed relation between the luminosity and mass of a star with predictions of stellar models.
(d) Comparing the observed oscillations of the Sun (helioseismology) with predictions of solar models.
(e) All of these are tests of stellar models.

Hertzsprung-Russell Diagram.

Visions of the Universe
Beth Hufnagel's home page, email: hufnage4@pilot.msu.edu
Bob Stein's home page , email: steinr@pilot.msu.edu