General Relativity (GR) is extremely successful on macroscopic scales, yet it predicts unphysical singularities at the centers of black holes. Within the phenomenological model of the Optico-Hydrodynamic Vacuum (OHV), gravity is treated not as metric curvature but as a local gradient of an effective vacuum viscosity etagrav (r) = GM / (r * c²). In the weak-field limit, this dissipation reproduces the standard gravitational redshift Delta E / E approx -GM / (r * c²) observed in Solar-System experiments, without any free factors. We show that the saturation limit of the medium (eta = 1, i. e. , 100% dissipation) triggers a vacuum phase transition (crystallisation), halting collapse at the critical radius rOHV = GM / c² = rS / 2. Although the physical boundary of the Black Star lies at rS / 2, the extreme refractive-index gradient of the viscous vacuum acts as a gravitational super-lens, bending photon trajectories so severely that the observed optical shadow matches the dimensions measured by the Event Horizon Telescope for M87* and Sgr A*. This eliminates the mathematical singularity and produces a macroscopic compact object — the Black Star — with a mass-dependent finite density rhoOHV = 3 * c⁶ / (4 * pi * G³ * M²). Since baryonic matter is itself a saturated phase of the vacuum substrate in the OHV framework, setting rhoOHV = rhoₙucl as a self-consistency requirement analytically predicts a critical mass for black hole formation of Mcrit approx 25. 4 Solar Masses, consistent with the dominant population of stellar-mass black holes detected by LIGO/Virgo. The model further predicts a frequency-dependent dispersion of gravitational redshift in ultra-strong fields, absent in standard GR.
Sergey Yurevich Paygachkin (Tue,) studied this question.