Black Hole Accretion

Black hole accretion disks are some of the most extreme environments in the Universe. Though black holes are themselves famously— black — it turns out that matter falling into them can emit enormous amounts of radiation and launch spectacular jets thousands of light years into interstellar space. Some of the basic ideas about black hole accretion have been around for decades, but only in the last few years as simulation techniques and computational resources have matured has it become reasonable to contemplate building ab initio models of these systems. Meanwhile, observational capabilities provide a torrent of data across the electromagnetic spectrum and it may even be feasible to directly image a black hole shadow in the coming decade. These are exciting times!

Go to the Black Holes Page for more information.

Collaborators: Charles Gammie, Hotaka Shiokawa, Monika Mościbrodzka, Alexander Tchekhovskoy, Scott Noble, Ben Ryan

Core-Collapse Supernovae

Core-collapse supernovae mark the deaths of massive stars. These violent events are interesting for a wide variety of reasons: they seed the cosmos with the heavy elements required by life, may regulate the formation of stars, and briefly emit about 1020 times more energy than the sun (mostly in neutrinos)! In the late stages of massive star evolution, a core of heavy nuclei forms that is supported primarily by electron degeneracy pressure. At some point, this core becomes too massive and, with the aid of electron capture, collapses on itself. As the central density surpasses the density of atomic nuclei, the strong nuclear force abruptly halts the collapse and the core rebounds, launching a shock wave into the collapsing stellar material. Much to the dismay of theoretical astrophysicists, it turns out that this shock stalls at a radius of about 200 km due to neutrino losses and the dissociation of heavy nuclei. The central problem in the theory of core-collapse supernovae for decades has been to elucidate the mechanism that revitalizes the shock and leads to stellar explosions like those observed. Unfortunately, the problem is incredibly challenging to solve largely because it inherently involves all four fundamental forces and a wide range of length and time scales.

Collaborators: Adam Burrows, Jeremiah Murphy, Weiqun Zhang, Ann Almgren, Christian Ott, Ernazar Abdikamalov, Jason Nordhaus