Astronomy 106 Quiz 8

1. Draw a diagram showing the parallax angle for (1) one of the closest stars (2) a star whose parallax can just barely be measured and (2) a star which shows no parallax

2. List everything you can think of which might make a star appear to be displaced from its plotted position on a star map.

3. What is the distance in parsecs and light years to a star whose parallax angle is .25”

4. What is the difference between brightness (apparent magnitude) and luminosity (absolute magnitude) of a star?

In the following be sure to include anything you can think of which might influence the answer, not just the obvious factors. Don’t worry about whether it is “right” or “wrong”

5. Suppose all stars are at the same distance from us, as was assumed in many ancient models of the celestial sphere. In this case, what factors might determine their how bright they appear to us?

6. Now suppose that all stars are at different distances. Again, what factors might influence how bright they appear to us?

7. Can you think of a way that the stars could be actually be at different distances, but that this difference not affect their relative brightness? In other words consider any two stars. Call them “A” and “B”. In the hypothetical universe under consideration here, if star “A” appears to be brighter than star “B”, you can always be certain that star “A” is more luminous (has a greater intrinsic brightness) than star “B”, even though they may be at different distances from us. How could this be possible?