"Nature," August 2009

"Nature" is a magazine of rather venerable scientific importance.  I don't normally put magazines here as I read too many of them and they are generally not of interest to me again in the future (although there have been exceptions).  This issue is focused on packaging Platonic Solids (a special case in packaging irregular shapes), but the article that has captured my attention is "The Diversity of Type Ia Supernovae From Broken Symmetries" by D. Kasen, F.K. Ropke, and S. E. Woosley.

Started:  April, 2010
Completed: April, 2010
Recommendation: For physics geeks interested in high pressure/density non-laminar gaseous flow only.  Oh, and really, really big explosions.
Recommended By: My wife found this one in a used section of the library and picked it up for me.

Words I looked up:
Reynolds Number - ratio of inertial forces  to viscous forces  is how Wikipedia makes the definition.  In short, this number looks at how the fluid behaves relative to the density of that fluid.  I had forgotten what this number was from early chemistry.
critical Karlovitz Number -  this is from the CFD-online wiki.  In short this looks at the degree of combustion in a turbulent situation with the time it takes for the combustion to occur.  The number becomes "critical" when combustion is on the threshold of being eliminated (or started depending on which side of the burning you originate :) ).
Rayleigh-Taylor instability - Interaction between two fluids where the lighter fluid is pushing the heavier fluid.  As far as I can tell, this pretty much only occurs in stars.


Review:
This article makes the case that use of white dwarf explosions (caused by accretion of mass from a nearby binary) do not necessarily provide the accurate "candle" of distance for which they have historically been used.  In short, the prevailing assumption has been that the explosion has been spherical in nature starting from the center of the star.  Recent research that fails to take into account a lot of variables (such as the spin-rate of the star--there is an effort to handle these variables, although it is clearly inadequate) has demonstrated a 2% error in distance calculations using these stars.  From the description in the article it seems to me that the 2% error serves as a bottom, although the authors clearly state that their calculations can only account for up to a 2% error.

I want to put more thought into this article and read it a few more times, but I think I have something to contribute to this research.  I'd love to play with the simulation they have developed.  The simulation suggests that the consumption of fuel makes the star a huge dipole and I'm guessing that combined with irregularities caused by the accretion disk, this dipole would distort the characteristics of the explosion even more.  My thinking is that there would be huge pools of hydrogen around the equator of the star undergoing spontaneous combustion (and flow into the mantle) as the star starts to consume its own Ni creating a back pressure that gives the star a slight dumbbell shape for Ni and I think that would effect the dipole by creating two exit points for ejecta at the poles with the equator accepting the ejecta and further accelerating the speed of the combustion of the accretion material and probably causing some kind of flow back into the deep interior of the star inhibiting Ni consumption and causing even more dispersed explosion events then contemplated in the article.