Download Homework, November 16, 2006 AST110-6

Homework, November 16, 2006
AST110-6
Due Date: Tuesday, November 28, 2006
1. Chapter 12, Problem 23 to 28 [60pt]. Homes to Civilization? We do not yet know
how many stars have Earth-like planets, nor do we know the likelihood that such
planets might harbor advanced civilizations like our own. However, some stars can
probably be ruled out as candidates for advanced civilizations. For example, given
that it took a few billion years for humans to evolve on Earth, it seems unlikely that
advanced life would have had time to evolve around a star that is only a few million
years old. For each of the following stars, decide whether you think it is possible that
it could harbor an advanced civilization. Explain your reasoning in one or two
paragraphs.
a.
b.
c.
d.
e.
f.
A 10 Msun hydrogen-burning star.
A 10 Msun brown dwarf.
A 1.5 Msun hydrogen-burning star.
A 1.5 Msun red giant.
A 1 Msun helium-burning star.
A red supergiant.
2. Chapter 12, Review Question 6 [20 pt]. Briefly explain the changes that the Sun will
go through after it exhausts its core hydrogen. Be sure to explain both the changes
occurring in the Sun’s core and the changes visible from outside the Sun. What do we
mean by the stages we call hydrogen shell burning, helium burning, and double-shell
burning?
3. The following table lists the spectral type and luminosity of 10 stars (A to J)
[20pt].
a. Place the stars in the attached H-R diagram template according to their
spectral type and luminosity. Label the stars clearly, like the Star S (the
Sun) shown in the figure.
b. List the stars that are likely to be main-sequence stars,
c. supergiant or giants, and
d. white dwarfs.
Problem 3 continues in page 2.
Star
A
B
C
D
E
F
G
H
I
J
S
Spectral Type
G2
F5
A1
A2
K2
A0
B1
B1
M1
M4
G2
Luminosity (Solar Units)
1.6
7.4
26.0
0.002
0.37
60.0
100,000
23,000
38,000
0.005
1.0