  We study the conditions required to produce self-sustained detonations in
turbulent, carbon-oxygen degenerate plasma at low densities.
  We perform a series of three-dimensional hydrodynamic simulations of
turbulence driven with various degrees of compressibility. The average
conditions in the simulations are representative of models of merging binary
white dwarfs.
  We find that material with very short ignition times is abundant in the case
that turbulence is driven compressively. This material forms contiguous
structures that persist over many ignition times, and that we identify as
prospective detonation kernels. Detailed analysis of prospective kernels
reveals that these objects are centrally-condensed and their shape is
characterized by low curvature, supportive of self-sustained detonations. The
key characteristic of the newly proposed detonation mechanism is thus high
degree of compressibility of turbulent drive.
  The simulated detonation kernels have sizes notably smaller than the spatial
resolution of any white dwarf merger simulation performed to date. The
resolution required to resolve kernels is 0.1 km. Our results indicate a high
probability of detonations in such well-resolved simulations of carbon-oxygen
white dwarf mergers. These simulations will likely produce detonations in
systems of lower total mass, thus broadening the population of white dwarf
binaries capable of producing Type Ia supernovae. Consequently, we expect a
downward revision of the lower limit of the total merger mass that is capable
of producing a prompt detonation.
  We review application of the new detonation mechanism to various explosion
scenarios of single, Chandrasekhar-mass white dwarfs.
