  We report on 224 photometric measurements of Nereid, a small outer satellite
of Neptune. Our photometry covers 64 nights from 1987 to 1997 and is primarily
in the V-band; we also have 20 measurements in the U, B, R, and I bands. (1)
Nereid displays large-amplitude brightness variations with a total amplitude of
1.83 mag on time scales ranging from a few hours to roughly a year. (2) The
amplitude as well as the time scale of variation changes greatly from year to
year. (3) Nereid's variability is caused by high contrast albedo features along
with rotational modulation. (4) The changing amplitudes and time scales
demonstrate that the direction and magnitude of Nereid's rotational angular
momentum vector is not constant. (5) Such changes are predicted to arise from
chaotic rotation during every periapse passage provided that Nereid is more
than about 1% nonspherical and is spinning slowly. The match between prediction
and observation could be taken as strong evidence for chaotic rotation of
Nereid. However, the intranight variability cannot be readily explained by
chaotic rotation. (6) The colors of Nereid are U-V=0.84+-0.05, B-V=0.71+-0.04,
V-R=0.44+-0.03, V-I=0.72+-0.05, and V-K=1.6. (7) Nereid is likely either an
inner moon of Neptune kicked to its current orbit or a captured Kuiper Belt
Object or centaur, with the latter possibility being strongly preferred.
