Homework 3 Solutions
Astro 363
Each part worth 3 points except as noted.
1. Stellar radii and luminosity.
2
4
(a) Recall that L = 4R Tef f , thus R =
4
L /(4 Tef f ).
Stated as a ratio:
R
L
=
R
L
Tef f,
Tef f,
4 1/2
O5: R = 13.4R = 9.3 109 m
B0: R = 6.70R

Homework 10
Astro 363
Due Friday, November 1
1. Two protons approach each other with kinetic energy of 2 keV.
(a) What is the characteristic temperature for a gas where protons have KE of 2 keV?
(For an order of magnitude estimate, ignore numerical factor

Homework 8 Solutions
Astro 363
Each problem worth 3 points except as noted.
1. For a monatomic gas, the ratio of specic heats is = 5/3.
(a) The adiabatic temperature gradient for a monatomic gas is
dT
1
= 1
dr
2 dP T
T dP
=
P dr
5 dr P
We want to compare

Homework 1 Solutions
Astro 363
Each part worth 3 points.
1. The magnitude system.
(a) Two stars dier by a factor of 7.5 in apparent ux, thus:
F1 /F2 = 7.5
The magnitude dierence is:
m = 2.5 log(F1 /F2 )
= 2.2 mag
(b) Star A is 4.20 magnitudes brighter tha

Homework 2 Solutions
Astro 363
Each part worth 3 points.
1. Sirius ( CMa) has V = 1.47, parallax angle of 0 379 and BC = 0.09.
.
(a) d = 1/p = 2.64 pc. 1 pc = 3.26 light years, so d = 8.61 ly. 1 pc = 206265 AU
(because 1 AU subtends an angle of one arcsec

Homework 4 Solutions
Astro 363
Each part worth 3 points except as noted.
1. The gure in the assignment shows the radial velocity curve for a binary pair. The
orbital period is 49.7 days. Use the plot and the binary stars applet on the course
website to an

Homework 5 Solutions
Astro 363
Each problem worth 3 points except as noted.
1. The Sun has R = 6.9 108 m and M = 2 1030 kg.
(a) The Sun is basically spherical, so the volume is V = 4R3 /3. The average
density is thus = M /V = 1.45 g cm3 , only about 3/2 t

Homework 6 Solutions
Astro 363
Each problem worth 3 points except as noted.
1. The bright blue star Merope (23 Tau) is one of the Seven Sisters stars in the nearby
Pleiades star cluster. It has V = 4.16 and a parallax of p = 9.08 mas. It is a B6 star,
so

Homework 7 Solutions
Astro 363
Each problem worth 3 points.
1. The total pressure in a star is the sum of the gas pressure (from ions and electrons)
and the radiation pressure. We will use the fact that the Virial theorem relates the
thermal kinetic energ

Homework 9 Solutions
Astro 363
Each problem worth 3 points except as noted.
1. Each of the fundamental forces has a characteristic range over which interactions can
occur. A force carrier known as a virtual particle is created (apparently from nothing!)
a