G.3 The problem plotting ellipses has had unfixed
errors in it for a long time. Here are two of them.
Much of the code uses the values a and b before it sets them.
x[t_] = a Cos[t];
y[t_] = b Sin[t];
a = 3;
b = 9;
Of course this means the first time it is plotted it may be
wrong. Put the assignments to a and b first.
The question of whether Pluto is inside or outside Neptune's
orbit is tricky. Many people know that Neptune is currently the
outermost planet, and Pluto is inside. However, if you plot the given
ellipses with the sun being in the same focus of each (e.g., both in
the "right" focus, so both ellipses stretch out more to the left),
this does not happen. You have to plot the sun as one's left focus and
the other's right focus.