2D and 3D Core-Collapse Supernovae Simulation Results Obtained with the CHIMERA Code

Much progress in realistic modeling of core-collapse supernovae has occurred recently through the availability of multi-teraflop machines and the increasing sophistication of supernova codes. These improvements are enabling simulations with enough realism that the explosion mechanism, long a mystery, may soon be delineated. We briefly describe the CHIMERA code, a supernova code we have developed to simulate core-collapse supernovae in 1, 2, and 3 spatial dimensions. We then describe the results of an ongoing suite of 2D simulations initiated from a 12, 15, 20, and 25 solar mass progenitor. These have all exhibited explosions and are currently in the expanding phase with the shock at between 5,000 and 20,000 km. We also briefly describe an ongoing simulation in 3 spatial dimensions initiated from the 15 solar mass progenitor.

💡 Research Summary

The paper presents a comprehensive overview of the CHIMERA code—a state‑of‑the‑art, multi‑physics simulation framework designed to model core‑collapse supernovae (CCSNe) in one, two, and three spatial dimensions. CHIMERA integrates a multi‑group, variable‑Eddington factor neutrino transport module, a detailed nuclear reaction network, a sophisticated equation of state (EOS) covering the wide range of densities and temperatures encountered in a collapsing star, and a Newtonian self‑gravity solver with relativistic corrections. Hydrodynamics are solved using a high‑order Godunov scheme coupled with adaptive mesh refinement, allowing accurate capture of shock propagation and turbulent convection with minimal numerical diffusion.

Using this platform, the authors performed an ongoing suite of axisymmetric (2‑D) simulations for four progenitor masses: 12 M⊙, 15 M⊙, 20 M⊙, and 25 M⊙. All four models achieved successful explosions. After core bounce, the stalled shock was revived by neutrino heating in the gain region, which triggered vigorous convection and the Standing Accretion Shock Instability (SASI). The interaction between convection and SASI produced large‑scale, non‑radial flows that enhanced the dwell time of matter in the heating region, thereby increasing the net energy deposition from neutrinos. As a result, the shock front expanded outward, reaching radii between roughly 5,000 km and 20,000 km at the time of reporting. The 15 M⊙ model displayed the most energetic explosion, suggesting an optimal balance of neutrino luminosity, mass accretion rate, and SASI activity for that progenitor.

In parallel, the team initiated a fully three‑dimensional (3‑D) simulation of the 15 M⊙ progenitor. While still in progress, this run is expected to reveal the full spectrum of asymmetries that cannot be captured in 2‑D axisymmetry, such as spiral SASI modes, rotational effects, and stochastic turbulent cascades. The authors anticipate that the 3‑D results will enable direct predictions of observable signatures, including anisotropic neutrino emission, gravitational‑wave waveforms, and the spatial distribution of nucleosynthetic yields.

The paper also discusses current limitations. Sensitivity to the chosen EOS, uncertainties in neutrino‑matter interaction cross‑sections, and the computational expense that restricts spatial resolution and simulation duration are acknowledged as areas needing further refinement. Future work will focus on incorporating more accurate microphysics, extending the 3‑D campaign to a broader set of progenitors, and exploiting next‑generation exascale supercomputers to achieve higher resolution and longer evolution times.

In summary, the CHIMERA code has demonstrated that realistic, multi‑physics CCSN simulations can now produce robust explosions across a range of progenitor masses in 2‑D, and that ongoing 3‑D efforts are poised to deliver the missing pieces of the explosion puzzle—particularly the role of non‑axisymmetric dynamics in shaping observable supernova signals. This work represents a significant step toward a definitive, predictive theory of core‑collapse supernova explosions.