  M87 has been monitored with a cadence of 5 days over a 9 month-long span
through the near-ultraviolet (NUV:F275W) and optical (F606W) filters of the
Wide Field Camera 3 (WFC3) of the $\textit{Hubble Space Telescope}$. This
unprecedented dataset yields the NUV and optical light and color curves of 94
M87 novae, characterizing the outburst and decline properties of the largest
extragalactic nova dataset in the literature (after M31 and M81). We test and
confirm nova modelers' prediction that recurrent novae cannot erupt more
frequently that once every 45 days; show that there are zero rapidly recurring
novae in the central $\sim$ 1/3 of M87 with recurrence times $ < $ 130 days;
demonstrate that novae closely follow the K-band light of M87 to within a few
arcsec of the galaxy nucleus; show that nova NUV light curves are as
heterogeneous as their optical counterparts, and usually peak 5 to 30 days
after visible light maximum; determine our observations' annual detection
completeness to be 71 - 77\%; and measure the rate Rnova of nova eruptions in
M87 as $352_{-37}^{+37}$/yr. The corresponding luminosity-specific classical
nova rate for this galaxy is $7.91_{-1.20}^{+1.20}/yr/10^{10}L_\odot,_{K}$.
These rates confirm that ground-based observations of extragalactic novae miss
most faint, fast novae and those near the centers of galaxies. An annual M87
nova rate of 300 or more seems inescapable. A luminosity-specific nova rate of
$\sim$ $7 - 10/yr/10^{10}L_\odot,_{K}$ in ${\it all}$ types of galaxies is
indicated by the data available in 2023.
