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ASTR120
Homework 1 Solutions
Ch. 1, Prob. 20.
The diameter of the Sun is given as 1.4 x 1011 cm, and its distance to Proxima Centauri is 4.2
ly. If we were to model the Sun using a 30 cm ball we can find the scaled distance to Proxima
Centauri by cross

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ASTR120
Homework 2 Solutions
Ch. 2, Prob. 37.
The Sun will pass 19 N on its way up to the Tropic of Cancer 23.5 N and on its way down
toward the equator and Tropic of Capricorn each year. So it will be over head at 19 N
exactly twice a year.
Ch. 3, Prob

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ASTR120
Homework 4 Solutions
Ch. 7, Prob. 24.
1
a. EK
mv2 where m is the mass and v is the velocity. We first need to find the mass of
2
the asteroid from problem 23.
mass
density x volume
V
3
4
4
Assuming a spherical asteroid, m
r3
2500
1 x103
1.0 x 1

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ASTR120
Homework 6 Solutions
Ch. 15, Prob. 42.
The rate of mass loss is 1000 kg s. Io has a mass of 8.932 x 1022 kg and it will lose 10 % of
that mass in its lifetime. So :
Mloss 0.1 MIo 8.932 x 1021 kg
Therefore :
mass loss
8.932 x 1021
8.932 x 1018 s

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ASTR120
Homework 5 Solutions
Ch. 12, Prob. 39.
To determine the angular resolution of the image, we can use the small angle formula :
206265 d
D
In this case, d is the finest detail the image shows and D is the distance the camera is
from the object. So

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ASTR120
Homework 3 Solutions
Ch. 5, Prob. 25.
To find the wavelength of maximum emission for the black hole, we need to use Wien s Law :
0.0029 K m
0.0029 K m
max
2.9 x 10 9 m
2.9 nm
T
106 K
This wavelength is in the X ray range of the electromagnetic s