We present the first three-dimensional general relativistic magnetohydrodynamic simulation of sustained accretion onto a horizonless singularity in which matter reaches the central object rather than being accumulated outside of it or expelled in outflows. We consider a Joshi-Malafarina-Narayan (JMN-1) spacetime, a well-motivated black hole mimicker that arises from gravitational collapse with anisotropic pressure in general relativity, and adopt a compactness parameter for which the central singularity is null. We find that the system evolves into a sustained magnetically arrested disk state. For parameters appropriate to the low-luminosity active galactic nucleus M87*, we obtain an accretion rate of ∼(3.0±0.5)×10−6M˙Edd, in full agreement with estimates based on black hole models and, in particular, comparable to that of our reference Schwarzschild black hole simulation. Synthetic ray-traced images at 230GHz, computed using polarized general relativistic radiative transfer, are broadly consistent with the Event Horizon Telescope observations of M87*. We identify a key observational discriminant between a black hole and JMN-1: the presence of detectable brightness inside of the ``observable" shadow of JMN-1. This emission originates very close to the central singularity, in a region that would be hidden behind the event horizon in a black hole spacetime. Although this signature is beyond the reach of current observations, it falls within the projected imaging dynamic range of next-generation radio interferometric instruments, offering a robust test of the black hole paradigm.
@article{arxiv.2604.15430,
title = {GRMHD accretion beyond the black hole paradigm: Light from within the shadow},
author = {Saurabh and Maciek Wielgus and Parth Bambhaniya and Elisabete M. de Gouveia Dal Pino and Andrei P. Lobanov and Pankaj S. Joshi},
journal= {arXiv preprint arXiv:2604.15430},
year = {2026}
}