Astro 465 Assignment 2
Due: 10 am Oct 3, 2016, in CCIS 2-107 or CCIS 4-285
(10pt) 2.1 Consider the constant density model:
(a) (7pt) Show how the virial theorem works for this constant density sphere, if we had to chosen to consider only
the part of the s
Astro 465: Stellar Astrophysics II
"I conceive that the chief aim of the physicist in discussing a theoretical problem is to
obtain insight - to see which of the numerous factors are particularly concerned in any
effect and how
The dynamical timescale dyn
We see on HRD that some stages of stellar evolution are very fast (like RG stage), so may
be there HE is not applicable? Lets assume that a start is not in HE. How fast then do
changes to the structure of a star occur?
The gravitational field
) gravity is the driving force behind stellar evolution.
In the general, non-spherical case, the gravitational potential is the solution of the Poisson equation
r2 ' = 4G
Another form (integral represen
Stellar dimensionless analysis
Homology, OR Homologous stars.
Consider a sequence of simple spherical stellar models in complete equilbrium where
one model is related to any of the others by a simple change in scale. Assume that the
models all have t
The virial theorem
The virial theorem is the most important consequence of selfgravitating bodies in hydrostatic equilibrium. The virial theorem connects two important energy reservoirs of a star
the gravitational potential energy of the star and sta
Solutions to HW 2
2.1 (constant density model)
(a) Consider equation for the potential energy, but integrate it only to radius r:
3 GM 2 5
The total kinetic energy is
3 dm = 12
For a constant
m ASSfnment 5'- Sold-cons
L \Iercfj 44w. «cutaway: relm+i0ns or 44% lower mam Sega-1mg
L 20 XLSS'Tl-I'L
R 20.1: X0. ml:
L 0 2-1.! X-sw MS-llv
Te * i x Mm:
USCAS +ke. dCMensroml analjsss approack +19 4kg S-lellar
ASSlahmt 1 - goLu-I-"ons
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" ~ 3
m = a , LAM-:wLo m.
M" L" whim 3222
.___. Giana )(mh.
Lo Mo La
a, xponeWJrsL -?-
I'dLi) .-.- Comsk exp(5.zxw 1g)
0 (MC-Hm inlLlaQ Candt'o
Mean molecular weight
Assume gas is composed by neutral atoms, ions, electrons with charge neutrality satisfied.
We would like to calculate the mean weight per particle in units of mu
Ions: denote with i each nuclear isotopic species.
Zi nuclear char