Homework 6 Astronomy 117
Due Wednesday, May 13
1. Show that a wind is inevitable for an isothermal atmosphere.
2. Using Cartesian coordinates, show that:
v v =
1 2
|v|
2
+(
v) v
(1)
3. Using standard parameters, nd the ratio of the speed of sound through

Homework 3 Astronomy 117
Due Wednesday, April 22
1. Assume that the opacity in the atmosphere of the Sun is 1.0 cm2 g1 . At optical
depth 2/3, what is the ratio of the energy density in the radiation compared to the energy
density in the gas?
2. We have s

Homework 7 Astronomy 117
Due Wednesday, May 20
1. Assume that the Sun has a coronal temperature of 1.0 106 K at a density of 1010
cm3 . Compute the mass loss rate from the Sun.
2. Assume that the outer boundary of the Solar wind is determined by the locat

Homework 4 Astronomy 117
due Wednesday, April 29
1. Assume a uniform, optically thin, cloud of dust around a star. If this dust scatters
isotropically, how does the surface brightness of the reflection nebulosity scale at angular
offset, ?
2. Consider an

Homework 5 Astronomy 117
Due Wednesday, May 8
1. Assume that the source of photo-ionization of a gas simply ceases. If ne = n(H + ),
then the equation for the time variation of the electron density is:
d ne
= n2
e
dt
(1)
Solve this equation for the bounda

Homework 8 Astronomy 117
Due Wednesday, May 27
1. The Galactic Center has a black hole with a mass of 4 106 M . If this black
hole is immersed within an interstellar medium of density 1024 g cm3 , and if this gas has
a ow velocity past the black hole of 1

Homework 1 Astronomy 117 Spring 2015
due in class Wednesday, April 8
1. The Sun has an apparent visual (0.55 m) magnitude of -26.74. What is its absolute
visual magnitude? If V = 0.0 mag corresponds to 3500 Jy, what is the surface brightness
of the Sun in