16.4  Why does the accretion disk around a neutron star have so much more energy than the accretion disk around a white dwarf even though both stars have approximately the same mass?

A neutron star is much smaller, so the material in the accretion disk can get much closer and go much faster.

16.7  What do we mean by the binding energy of an atomic nucleus?  How does this measurement help us to calculate the energy given off in nuclear fusion reactions?

Binding energy is the energy due to the strong force that holds nuclei together.  Moving up the periodic table to iron, each successive nucleus (except those immediately following helium) has less mass than the sum of the individual nucleons that make it up.  The mass difference is equivalent to the binding energy, so energy is released when nuclei are formed by fusion.

16.8 Explain two important ways that supernovae influence the formation and evolution of new stars.

Supernovae spread the heavy elements they make around the universe.  And their shock waves compress the interstellar medium, initiating the formation of new stars.

16.14  The Moon has a mass equal to 3.74 x 10^-8 M_Sun.  Suppose the Moon suddenly collapsed into a black hole.
             a.  What would be the radius of the event horizon around the black hole Moon?
             b.  What affect would this have on tides raised by the Moon on Earth?  Explain.
             c.  Do you think this event would or would not generate gravity waves?  Explain.

a.  A black hole the size of the Sun would have an event horizon with a radius of 3 km.  So a mass of 3.74 x 10^-8 M_Sun would have an event horizon with a radius of 3 x 10³ m x 3.74 x 10^-8 = 1.1 x 10^-4 m or 0.11 mm.

b.  No affect on tides.  The mass would be the same and its center would be in the same location.

c.  Yes, it would generate gravity waves - a highly compressed object is being created very quickly.