  The basic features of nucleus-acoustic (NA) envelope bright and dark
solitons, which exist in degenerate quantum plasmas, have been theoretically
investigated by deriving the nonlinear Schr\"odinger (NLS) equation. The
reductive perturbation method, which is valid for a small but finite amplitude
limit, is employed. It is found that the bright envelope solitons are
modulationally unstable, whereas the dark ones are stable. It is also observed
that the fundamental properties (viz. Modulational instability (MI) growth
rate, width and energy concentration of NA waves, etc.) of NA unstable bright
envelope solitons are significantly modified by constituent particles number
density. The implications of our results obtained from our present
investigation in astrophysical compact objects like white dwarfs and neutron
stars are briefly discussed.
