Computational Astrophysics

The stalled blast wave (in blue) encompassing the turbulent region external to a newly-born neutron star just before the onset of a supernova explosion. The scale is ~200 kilometers on a side.
"The Overarching Framework of Core-Collapse Supernova Explosions as Revealed by 3D Fornax Simulations," (Adam Burrows, David Radice, David Vartanyan, Hiroki Nagakura, M. Aaron Skinner, & Joshua C. Dolence), MNRAS, 491, 2715-2735, 2020 (arXiv:1909.04152) doi.org/10.1093/mnras/stz3223
A still of the bubble and plume structures that define the core-collapse explosion debris. The colors reflect different degrees of neutron-richness which translate into an anisotropic element distribution. The tracers are representative matter streams associated with the blast. The scale is a few thousand kilometers only ~1 second after the onset of the supernova blast in the core of a massive star.
"A Systematic Study of Proto-Neutron Star Convection in Three-Dimensional Core-Collapse Supernova Simulations," (H. Nagakura, A. Burrows, D. Radice, & D. Vartanyan), MNRAS, 492, 576, 2020 (arXiv:1912.07615). %% doi = {10.1093/mnras/staa261}
A still of the bubble and plume structures that define the core-collapse explosion debris, highlighting both the debris field and the shock wave. The colors reflect different degrees of neutron-richness which translate into an anisotropic element distribution. The tracers are representative matter streams associated with the blast. The scale is a few thousand kilometers only ~1 second after the onset of the supernova blast in the core of a massive star.
"On the Origin of Pulsar and Magnetar Magnetic Fields," (Christopher J. White, Adam Burrows, Matthew S.B. Coleman, and David Vartanyan), Ap.J., 926, 111, 2022, arXiv:2111.01814 (doi.org/10.3847/1538-4357/ac4507).
Volume rendering of the current density in the entire domain at a stage when turbulence is fully developed. Myriad of current sheets is evident in the plane perpendicular to the mean magnetic field Bz0. Source
Volume rendering of the current density in the entire domain at a stage when turbulence is fully developed. Myriad of current sheets is evident in the plane perpendicular to the mean magnetic field Bz0. Source
Kelvin-Helmoltz instability simulation in two space dimensions using a fourth-order finite element method. These images show a zoom sequence with progressively more details. This novel numerical method, called Spectral Difference with a posteriori limiting, was developed in our Department by David Velasco and Romain Teyssier. It works at any arbitrary high-order (up to ten in practice) and runs on GPUs. Source

Computation has become an essential tool in theoretical astrophysics modeling, and Princeton is a world leader in the development and application of numerical methods in astrophysics.

Researchers at Princeton use scientific computation to study an enormous range of physical processes. At the largest scales, N-body, hydrodynamic, and radiative transfer methods are used to study cosmological structure formation, galaxy formation, and the epoch of reionization (R. Cen, E. Quataert, R. Teyssier). At the smallest scales, particle-in-cell (PIC) methods are used to follow particle acceleration, kinetic turbulence, and microscale instabilities in dilute astrophysical plasmas (M. Kunz, A. Spitkovsky, E. Ostriker, E. Quataert). In between, a wide variety of numerical methods are used to understand core-collapse supernova explosions (A. Burrows), accretion onto compact objects (A. Burrows, A. Spitkovsky, E. Quataert, J. Stone), gravitational fragmentation of turbulent molecular clouds and star formation (E. Ostriker, J. Stone, R. Teyssier), protostellar accretion disks and winds (M. Kunz, E. Ostriker, J. Stone), the interaction of stellar feedback in the form of radiation and cosmic rays with interstellar gas (E. Ostriker, J. Stone, R. Teyssier), the solar wind (M. Kunz), and the light scattering properties of interstellar dust grains (B. Draine), just to name a few.

Astrophysicists at Princeton do not merely run public domain codes, but rather they are leading efforts to develop, implement, and test new state-of-the-art algorithms in many areas. Important methods developed at Princeton include adaptive particle-mesh codes for collisionless dark matter (R. Teyssier), hydrodynamic and radiative transfer codes to study planet atmospheres (A. Burrows) and reionization (R. Teyssier), a variety of grid-based MHD and radiation hydrodynamic codes to study everything from the star-forming interstellar medium (E. Ostriker, J. Stone, R. Teyssier) to compact-object accretion disks (J. Stone) to supernovae (A. Burrows), and PIC and gyrokinetic codes to study plasma dynamics (G. Hammett, M. Kunz, A. Spitkovsky). Members of the department are collaborating in various projects led by F. Pretorius in the Princeton Physics department to develop codes to simulate dynamical spacetimes and black-hole mergers. The department is leading the international effort in developing open source community codes such as RAMSES and ATHENA.

The department benefits from close ties with the Program in Applied and Computational Mathematics and the Princeton Institute for Computational Science and Engineering (PICSciE), which houses one of the most powerful collections of high-performance computing systems at any university in the country. These systems are freely available for use by any on-campus researcher, and some of our graduate students have used several million cpu hours per year for their thesis work. Members of the department also have access to emerging petascale systems at DOE, NASA and NSF national supercomputing centers. Students at Princeton receive a solid education in numerical analysis and software engineering through courses offered in the department, and in collaboration with PICSciE. A certificate in scientific computation is offered through the graduate school.

Evolution of the emission measure in a radiation hydrodynamic simulation of a cluster-forming giant molecular cloud, computed using adaptive ray tracing methods. Regions of high emission measure mark the surfaces where gas is being photo ionized by the UV radiation from the star cluster particles (with positions marked); the dense molecular gas in the cloud is photo-evaporated and dispersed rapidly as soon as luminous stars form, quenching future star formation. From Kim, Kim, & Ostriker (2018) Source
Three-dimensional visualization of the heliospheric termination shock (HTS) and heliopause (HP) surfaces. a,b, Surfaces of the HTS and HP as viewed from outside the front/ upwind direction (a) and the port side (b). Surfaces are derived from data sky maps smoothed and interpolated to a 2° × 2° resolution grid using Kriging interpolation. Only pixels within 54° of the 255° meridian line are shown. Arrows in the direction of Voyager 1 (top grey), Voyager 2 (bottom grey) and local interstellar medium (LISM) inflow directions (red) are also shown.

Zirnstein, E. J., Shrestha, B. L., McComas, D. J., Dayeh, M. A., Heerikhuisen, J., Reisenfeld, D. B., Sokół, J. M., Swaczyna, P., Oblique and rippled heliosphere structures from the Interstellar Boundary Explorer, NatAs, doi:10.1038/s41550-022-01798-6, 2022. Source
Volume rendering of a supernova explosion from a rapidly rotating, highly magnetized stellar core with its magnetic field slightly misaligned from its spin axis. The colors indicate specific entropy, where red is high entropy. These jetted explosions known as MHD or magneto-rotational supernovae are suggested sites of heavy element (e.g. gold, platinum) nucleosynthesis through a process known as the r-process. 3D general-relativistic MHD simulations with dynamical spacetime evolution, like the one used to produce this image, are necessary to determine the relative contribution of this type of event to abundances of heavy elements in the universe. Source
Star-forming rings produced in the nuclear regions of spiral galaxies. Results shown intercompare results for different time-varying bar-driven inflows. From Moon, Kim, Kim, & Ostriker (2022) Source