AstronomyTeacher

1. Return papers.
2. review responses to exam replacing planet test o/r
3. return h-r diagrams, answer questions, turn in.
4. brightness lab followup-questions - reassign, due friday. If you've already done it, don't redo it.

Brightness vs. distance questions for post-lab and pre-qualifiers:
(This is homework)

1. If a light source is measured with a light probe at a distance of 2 meters and reads 1500 lumens (a brightness unit similar to what our probes report) what will it read at a distance of:
a. 4 meters?
b. 10 meters?
c. 100 meters?
d. 1,000,000 meters?

2. Why is the brightness and distance relationship called the "inverse square law"? What is an "inverse square"?

3. Two stars are observed through a telescope using a CCD camera. The first star (A) is 10 light years away and is known to be identical to star (B). Star B is observed to be 1/25 as bright as star A even though it is identical. How far away is star B?

4.Two stars are observed, and they appear to be the same brightness on a CCD. Star C is magnitude 5, and Star D is magnitude 10.
a. Which one is brighter?
b. How many times brighter is it?
c. How many times farther away is the dim one?

5. Consider two real stars. Kruger 60 B is magnitude +11.3, and Barnard's star is magnitude +9.54.
a. Which one is brighter?
b. What is the magnitude difference?
c. How many times brighter is the bright one?
d. How many times dimmer is the dim one?
e. The parallax of Barnard's star is 0.549. How far away is it in parsecs?
f. How far away is Kruger 60?