Download Homework, August 29, 2002 AST110-6

Homework, November 9, 2006
AST110-6
Due Date: Thursday, November 16, 2006
1. If nuclear fusion of hydrogen in the core of the Sun were to stop now, what would we
see on the surface of the Sun tomorrow? Why? Will we be able to tell that hydrogen
burning in the core has stopped? How? (20pt)
(Hint: What particles that are generated by the fusion of hydrogen can escape
from the interior of the Sun immediately?)
2. Chapter 11, Review Question 7. What is the defining characteristic of a main-sequence
star? How is surface temperature related to luminosity for main-sequence stars? (20pt)
3. Is this statement sensible? Why, or why not? (20pt)
If the Sun had been born as a high-mass star some 4.6 billion years ago, rather than as
a low mass star, the planet Jupiter would probably have Earth-like conditions today,
while earth would be hot like Venus.
4. Chapter 11, Problem 26. Stellar Data. Consider the following data table for several bright stars.
M v is absolute magnitude, and m v is apparent magnitude. (Hint: Remember that the magnitude
scale runs backward, so that brighter stars have smaller (or more negative) magnitudes.) (40pt)
Star
Mv
mv
Spectral Type
Luminosity Class
Aldebaran
-0.2
+0.9
K5
III
Alpha Centauri A
+4.4
0.0
G2
V
Antares
-4.5
+0.9
M1
I
Canopus
-3.1
-0.7
F0
II
Fomalhaut
+2.0
+1.2
A3
V
Regulus
-0.6
+1.4
B7
V
Sirius
+1.4
-1.4
A1
V
Spica
-3.6
+0.9
B1
V
Answer each of the following questions, including a brief explanation with each answer.
a. Which star appears brightest in our sky?
b. Which star appears faintest in our sky?
c. Which star has the greatest luminosity?
d. Which star has the least luminosity?
e. Which star has the highest surface temperature?
f. Which star has the lowest surface temperature?
g. Which star is most similar to the Sun?
h. Which star is a red supergiant?
i. Which star has the largest radius?
j. Which stars have finished burning hydrogen in their cores?
k. Among the main-sequence stars listed, which one is the most massive?
l. Among the main-sequence stars listed, which one has the longest lifetime?