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Carbon detonation is a characteristic event of Type 1a Supernova (EDIT: where an accreting white dwarf near the Chandrashankar limit of 1.4 solar masses explodes), an extremely important standard candle for cosmology. An area of active research is designing computer simulations to model supernova spectra and light curves and fit these to ones obtained observationally to better understand the effect of trace elements and characteristics of the explosion (asymmetry, companion star properties, etc) in order to provide better distance estimates to get more accurate constraints on cosmological parameters (Hubble constant, Dark Energy equation of state, etc).

But it would be very interesting (and extremely cool) if there was a way of generating carbon detonations in a laboratory situation in order to study these effects. What sort of temperature/pressure range is necessary to generate a carbon detonation? Would it be in the range of experimental apparati? Or, on the extreme sides of things, a large thermonuclear device?

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2 Answers 2

In stars, carbon-carbon fusion gets going around $5\times10^8\,\text{K}$. From a quick glance at a relevant stellar model I have lying around, it looks like the relevant pressure in the core of a $12M_\odot$ star is on the order of $10^{22}\,\text{dyne.cm}^{-2}$ or $10^{21}\,\text{Pa}$. But the densities are also very large: around $10^6\,\text{g.cm}^{-3}$ and the reaction rate scales with $\rho^2$.

As far as I know, the temperatures and densities achieved in the National Ignition Facility are around $10^8\,\text{K}$ and $10^3\,\text{g.cm}^{-3}$. So while it doesn't seem that the temperatures are that hard to reach, the densities probably are.

Our current knowledge of these reaction is built on detailed calculations and collider experiments with small numbers of particles. These collisions aren't nearly enough to produce energy but we can learn something about the reaction cross-sections based on what happens.

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The trick with colliders is they are often too energetic (per particle), and so comparison with stellar interiors requires a disconcerting amount of extrapolation. –  Chris White Dec 3 '12 at 0:36

I'm finding two differing definitions online

In either case, I think that we can say that the full process is a thermonuclear explosion (and hotter, more energetic one than the wimpy hydrogen/helium ones we use for bombs at that). That is scary bad.

The individual carbon-carbon fusion events can be simulated in a particle physics context with a medium energy ion accelerator, but the resulting data is a long, long way from giving you the full picture of the process you wish to investigate.

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I don't quite trust the first definition given. In all literature I've seen a carbon detonation has refereed to the second definition (an accreting white dwarf near the chandrashankar limit of 1.4 solar masses). I will edit my question to make this clear. I understand it is a thermonuclear process, I am wondering if there is a way to calculate the necessary pressures and a comparison to pressures able to be generated with laboratory experiments or thermonuclear bombs. (Not that I am considering revoking the nuclear testban treaty for the purpose of cosmology :P ) –  Benjamin Horowitz Jun 25 '12 at 18:51

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