The
4 equations of stellar structure
are the basic equations
of hydrostatic
stellar structure.
They must be solved simultaneously on the computer.
But these are just the basic equations for the very basic
stellar structure
of main sequence stars.
They do NOT account for:
stellar rotation,
3-dimensional convection
(they approximate
1-dimensional convection, but
this approxiamtion is a weak point),
stellar magnetic fields,
asteroseismology
(of which a special case is
helioseismology),
starspots
(of which a special case are
sunspots),
stellar activity
(i.e., star of which a special case is
solar activity:
i.e., Sun),
the centrifugal force,
the Coriolis force,
close binary system effects,
leftover star formation effects,
stellar evolution,
post-main-sequence evolution
In fact, writing a
computer code for
solving the
4 equations of stellar structure
with simplified physics ingredients
is a graduate student course project.
It's relatively easy.
Doing state of the art
stellar structure calculations
is, of course, very hard.
The 4 equations of stellar structure
are differential equations
that embody
physical law.
To expand on the last sentence, see the insert below
(local link /
general link: physical_law_solution.html).
Caption: To illustrate the solutions of
differential equations,
see the
animations
showing the
projectile motion
trajectories
for an inclined launch
with NO drag
(black),
Stokes law drag
(blue),
and
Newton drag
(green).
Launch angle = 70° and
in natural units
little g = 1,
launch speed v = 1.25,
and terminal velocity for
both drag types vmax=0.65.
The trajectories are solved for
from differential equations:
simple analytically in the case of
NO drag,
not-so simple analytically in the case of
Stokes law drag,
and by numerical solution in the case of
Newton drag
which has NO exact analytic solution it seems
(Wikipedia:
Projectile Motion: Trajectory of a projectile with Newton drag).
Credit/Permission: ©
User:Greek3,
2020 /
Creative Commons
CC BY-SA 4.0.
Image link: Wikimedia Commons:
File:Inclinedthrow2.gif.
Local file: local link: stellar_structure_4_equations.html.
File: Star file:
stellar_structure_4_equations.html.