  Understanding the physics of the deep solar interior, and the more exotic
environs of core-collapse supernovae (CCSN) and binary neutron-star (NS)
mergers, is of keen interest in many avenues of research. To date, this physics
is based largely on simulations via forward integration. While these
simulations provide valuable constraints, it could be insightful to adopt the
"inverse approach" as a point of comparison. Within this paradigm, parameters
of the solar interior are not output based on an assumed model, but rather are
inferred based on real data. We take the specific case of solar electron number
density, which historically is taken as output from the standard solar model.
We show how one may arrive at an independent constraint on that density profile
based on available neutrino flavor data from the Earth-based Borexino
experiment. The inference technique's ability to offer a unique lens on physics
can be extended to other datasets, and to analogous questions for CCSN and NS
mergers, albeit with simulated data.
