Download Discussion Activity #10

Name:
_______________________________________
Section: _______________________________________
ASTR100
Nov. 7/9, 2005
Discussion Worksheet #10
For the use of the TA: Was this student present at the beginning of class?
Yes
No
Please choose the best answer. You may refer to any materials you have with you, and you may
work in groups.
1. Suppose two stars are identical except that one is twice as far away from us as the other.
Which statement is true?
A. Both stars have the same luminosity, but the apparent brightness of the closer star is four
times as great as that of the more distant star.
B. Both stars have the same apparent brightness, but the luminosity of the closer star is four
times as great as that of the more distant star.
C. Both stars have the same luminosity, but the apparent brightness of the closer star is twice
as great as that of the more distant star.
D. Both stars have the same luminosity, but the apparent brightness of the more distant star
is four times as great as that of the closer star.
2. Suppose star A has a parallax angle of 1/20 of an arcsecond and star B has a parallax angle of
1/40 of an arcsecond. What can you say about the relative positions of stars A and B?
A.
B.
C.
D.
Star A is farther away
Star B is farther away
They are the same distance away.
Their relative positions cannot be determined.
…continued on other side
3. To answer the following questions, refer to the labels (a) through (e) on the following sketch
of an H-R diagram. [Note that choice (a) refers to the entire main sequence, while (c) and (d)
refer to only small parts of the main sequence. If choices (c) or (d) offer better answers to the
question than (a), use the best choice.]
Which group represents stars that are cool and dim?
Which group represents stars of the largest radii?
Which group represents the most common type of stars?
Which group represents stars with the shortest main-sequence lifetimes?