Sean Couch

Associate Professor of Physics

About

  • Joined the laboratory in June 2015
  • Theoretical nuclear astrophysics
  • Contact information

Education and training

  • MA, Astrophysics, The University of Texas at Austin, 2008
  • PhD, Astrophysics, The University of Texas at Austin, 2010

Research

My research centers around unraveling the mystery of
how massive stars explode at the end of their lives. Such
core-collapse supernova explosions are responsible for
the production of most of the elements beyond hydrogen
and helium throughout the Universe and play a crucial
role in providing feedback mechanisms to galaxy and
star formation. While supernovae are observed routinely
to occur in galaxies near and far, the physical mechanism
that drives these energetic explosions remains unclear.
My study of the core-collapse supernova mechanism uses
cutting-edge computational methods executed on the
world’s largest supercomputers.

The most promising candidate for the supernova
explosion mechanism is the so-called “delayed neutrino
heating” mechanism. Neutrinos carry away nearly all of
the gravitational binding energy released via the collapse
of the stellar core, about 100 times the energy necessary
to drive robust supernova explosions. The trouble is
that neutrinos have an incredibly tiny cross section for
interaction, making extracting much of this copious
energy extremely difficult. The most sophisticated 1D
simulations have, for decades, shown that the neutrino
mechanism fails in spherical symmetry. The situation
is somewhat more promising in 2D and 3D wherein a
handful of self-consistent explosions have been obtained,
but these explosions tend to be marginal.

Much of my recent work has focused on the role of
turbulence in the supernova mechanism. Turbulence
behind the stalled supernova shock, driven by the neutrino
heating, is extremely strong and violent. This turbulence
exerts an effective pressure on the stalled shock that can
revival the background thermal pressure. This is a huge
effect that is completely missing from 1D calculations! My
collaborators and I showed that 2D and 3D calculations
require much less neutrino heating to reach explosions
precisely because of this turbulent pressure helping
to push the shock out. I am currently investigating the
requirements for accurately modeling turbulence in the
simulations of the supernova mechanism.

Another aspect of my research is understanding how
convection in the cores of supernova progenitor stars
can influence the explosion mechanism. How strong such
convection is in real massive stars was uncertain since
the state-of-the-art in supernova progenitor calculations
is still 1D models. My collaborators and I made the first
steps forward in addressing these issues by carrying out
the world’s first 3D supernova progenitor simulation,
directly calculating the final three minutes in the life of
a massive star all the way to the point of gravitational
core collapse. We showed that the resulting strongly
aspherical progenitor structure was more favorable for
successful CCSN explosion than an otherwise identical 1D
progenitor.

Together with my collaborators around the country, I am
leading a cutting-edge effort to produce the world’s first
and most realistic 3D supernova progenitor models. This
work involves the combination of best-in-class opensource
stellar evolution modeling codes with a 3D nuclear
combustion hydrodynamics code, and the world’s fastest
supercomputers.

Scientific publications