Download Oct 06, 2001

Examine the hypothetical stars listed below. Refer to these stars in answering the following
questions.
Distance
Spectral
Luminosity
Star
m
M
Parsecs
Type
Class
A
11.05 15.5
1.3
M5
V
B
0.91
-3.6
80
B1
V
C
-0.3
-0.3
10
K2
III
D
1.79
-6.8
491
O9
I
E
1.26
-6.9
429
A2
I
1. Which of the stars listed above is appears the dimmest?
A
B
C
D
E
2. Which of the stars listed above is the most luminous?
A
B
C
D
E
3. Which of the stars listed above is the hottest?
A
B
C
D
E
4. Which of the stars listed above is the largest in radius?
A
B
C
D
E
5. Which of the stars listed above is the closest?
A
B
C
D
E
6. Which of the stars listed above is 10 parsecs away?
A
B
C
D
E
7. Which of the stars listed above is a main sequence star?
A
B
C
D
E
8. Which of the two stars D or E is closer?
A
B
C
D
E
The questions below refer to the HR diagram on the next page.
9. Which of the lettered stars on the HR diagram is most like the Sun?
A
B
C
D
E
10. Which of the lettered stars on the HR diagram is least likely to be one of the bright stars you
see at night?
A
B
C
D
E
11. Which of the lettered stars would be a blue supergiant?
A
B
C
D
E
12. Which of the lettered stars on the HR diagram is about 100 times more luminous than the
Sun?
A
B
C
D
E
13. Briefly describe what changes in temperature and radius must occur to Star C to transform it
into Star E?
14. Briefly describe what changes in temperature and radius must occur to Star E to transform it
into Star A?
15. Image that you are the star labeled Star D. Tell me about yourself. Describe your physical
characteristics and any noteworthy features or properties you possess.
16. The original form of the Sun’s luminosity is in deadly gamma rays. Please explain why we
are not harmed by those gamma rays.
NOTE: The HR diagram the questions above refer to is NOT shown.
17. The HR Diagrams for two open clusters are shown below. Please identify which Open
Cluster is the oldest and justify your choice using your knowledge of stellar evolution.
Open Cluster M 67
Open Cluster NGC 6530
8
5
7
10
9
V
V
12
11
14
13
16
15
18
-0.5
0
0.5
B-V
1
1.5
2
2.5
17
-1
0
1 B-V
2
3
4
18. There are reported to be about 6,000 stars visible to the naked eye. How many of those stars
would you expect to be part of a multiple star system?
Answer
Essay Questions
19. The Sun has a limited lifetime. In the space below, please justify this statement by detailing
the process of energy generation in the Sun and describing why the Sun has a limited
lifetime.
20. I have heard it said that the Sun is a “typical” star in the Milky Way galaxy. Please make an
argument below citing specific characteristics of the Sun and the most common types of
stars in the Milky Way galaxy to either support or refute this statement.
Answer all questions on the exam in the provided spaces. Use the Scantron
answer sheet to record your answers.
Refer to these stars in the table below in answering the following questions. There may be more
than one correct answer to some of the following questions. Choose all that apply.
Spectral
Luminosity
Star
m
M
Type
Class
A
1.29
-5.2
A2
II
B
0.91
-3.6
B1
V
C
11.05 15.5
M5
V
D
1.36
-6.8
O9
I
E
-0.3
-0.3
K2
III
1) Which of the stars listed above is appears the dimmest?
2) Which of the stars listed above is the most luminous?
3) Which of the stars listed above is the hottest?
4) Which of the stars listed above is the largest in radius?
5) Which of the stars listed above is the closest?
6) Which of the stars listed above is 10 parsecs away?
7) Which of the stars listed above is a main sequence star?
8) Which of the two stars D or E is closer?
9) Which of the stars listed above has the longest remaining lifetime?
10) Which of the stars listed above has a spectral type different from its original spectral type?
The HR Diagram at right is provided to assist with answering the following two questions.
Spectral Type
O5
10,000
B5
A5
K5
M5
Red Giants
a
d
1,000
Luminosity (solar units)
F5 G5
-5
b
100
0
10
Main
Sequence
1
e
5
.1
.01
f
12) Which statement is the most correct
.001
about the comparison between a K5
.0001
main sequence star and a B5 main
sequence star?
20,000
10,000
5,000
A) The K5 star is cooler, less
Temperature (K)
luminous, smaller, and will not
live as long as the B5 main sequence star.
B) The K5 star is hotter, less luminous, larger, and will live longer than the B5 main sequence
star.
C) The K5 star is smaller, hotter, more luminous, and will not live as long as the B5 main
sequence star.
D) The K5 star is hotter, more luminous, smaller, and will live longer than the B5 main
sequence star.
E) The K5 star is less luminous, cooler, smaller, and will live longer than the B5 main
sequence star.
10
c
White Dwarfs
This is a” thinking” question: Star A appears brighter than Star B, but Star A actually gives off
less energy than Star B. The apparent magnitude and absolute magnitudes for Star A are m = 1
and M = -2, respectively. Use this information to answer the following two questions.
13) Which of the following are the best possible values for the apparent and absolute magnitudes of
Star B?
A) m = -1 and M = 2
C) m = 3 and M = 2
B) m = -1 and M = -4
D) m = 3 and M = -4
14) Which is the most correct statement about the distance of Star A from Earth?
A) Star A is closer than 10 pc from Earth.
B) Star A is exactly 10 pc from Earth.
C) Star A is farther than 10 pc from Earth.
-------------------------------------------------------------------------------------------------------------------------------
15
Absolute magnitude
11) Which is hotter, a main sequence star
with an absolute magnitude of M= 4
or a white dwarf with a luminosity
100 times smaller than the Sun?
A) the main sequence star
B) the white dwarf
C) They have the same temperature.
D) There is insufficient information
to determine this.
Imagine you are comparing the five stars (A-E, shown below) of different radii and temperatures.
The temperature of each star is indicated by a shade of gray (as shown at right), such that the lighter
the shade of gray, the higher the temperature of the star.
High
Medium
A
B
C
D
E
Low
15) Which of the following is the most correct ranking for the luminosity of these stars from
greatest to least?
A) C > E > A >B > D
B) D > B > A >E > C
C) C > E > B >A > D
D) E > C> A >B > D
E) C = E > A =B > D
16) How does the Sun produce the energy that heats our planet?
A) The gases inside the Sun are burning and producing large amounts of energy.
B) Hydrogen is combined into helium, giving off large amounts of energy.
C) Gas inside the Sun heats up when compressed, giving off large amounts of energy.
D) Heat trapped by magnetic fields in the Sun is released as energy.
E) The core of the Sun has radioactive atoms that give off energy as they decay.
17) If the stars Betelgeuse and Rigel were to have the same luminosity but the temperature of
Betelgeuse is cooler than Rigel, which star has the greater surface area?
A) Betelgeuse
D) There is insufficient information to
B) Rigel
answer this question.
C) They are the same size.
Use the four HR diagrams shown below to answer the following two questions.
Star Pleiades
Cluster A
Star MCluster
B
67
6
8
8
10
10
V
12
V
12
14
14
16
16
18
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
18
2
0
B-V
0.2
Star Cluster
C
M3
0.4
0.6
0.8
1
B-V
1.2
1.4
1.6
1.8
2
Star Cluster
D
M35
8
13
14
10
15
16
12
V
V
17
14
18
19
16
20
21
18
0
22
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0.2
0.4
0.6
0.8
1
1.2
1.4
B-V
B-V
29) Which of the following is the most correct ranking for the age of the star clusters from youngest
to oldest?
A) A<B<C<D
C) C<B<A<D
B) D<C<A<B
D) D<A<B<C
30) Which of the star clusters in the HR diagrams has a large number of stars that are producing
energy by core He-burning?
A) Star Cluster A
C) Star Cluster C
B) Star Cluster B
D) Star Cluster D
32) Proxima Centauri is a main sequence star that appears red when viewed from Earth,
as a result which of the following are true:
A) It is hotter than an O spectral class main sequence star.
B) It is moving toward the Earth.
C) It is moving away from the Earth.
D) It will live longer than a B spectral class main sequence star.
E) It is the same size as a red giant star of the same temperature.