magicjava wrote:Question 1: Does anyone know of any papers that would show whether or not plasma recombining in this way would produce a blackbody curve like the sun is known to produce?
Following in Balfour Stewart's footsteps, Gustav Kirchhoff canonized the essential characteristics of different types of EM radiation in his three laws of spectroscopy.5,6
- A hot solid object produces light with a continuous spectrum (i.e., black-body radiation). (Wilhelm Wien went on to say that the power distribution has a bell curve that depends on the temperature.7)
- A hot tenuous gas produces light with spectral lines at discrete frequencies, and in combinations that depend in a more complex way on the temperature. (Niels Bohr later developed the concept of electron shells, and traced the spectral lines down to the degrees of ionization in the gas, which are a function of temperature.8)
- A hot solid object surrounded by a cool tenuous gas produces black-body radiation, but with gaps at discrete frequencies (which are the same as the emission frequencies of the gas, and likewise depend on the degree of ionization).
More recent research has demonstrated that supercritical fluids, well above their boiling points but under sufficient pressure to still be at or near their liquid densities, produce BB radiation.17
Instead of covalent bonds constraining the motion of atoms, Coulomb forces between closely packed ions do the same thing. So instead of a crystal lattice, it's a Coulomb lattice, so to say. The greater the pressure, the closer the atoms, and the higher the frequency of vibration, even with the same atomic speeds. So Kirchhoff's "4th
law" should have been that a hot, high-pressure plasma does not produce spectral lines (because of a lack of bound electrons), but it does produce BB radiation (from the oscillations of atomic nuclei with short mean free paths).
Since the Sun is comprised of hot, high-pressure plasma, this emerging "4th
law" explains solar BB radiation. Plasma recombination produces only spectral lines, per Kirchhoff's 2nd
5. Kirchhoff, G., 1860: Ueber das Verhältniss zwischen dem Emissionsvermögen und dem Absorptionsvermögen der Körper für Wärme and Licht. Annalen der Physik und Chemie, 109: 275-301
6. Robitaille, P. M., 2003: On the validity of Kirchhoff's law of thermal emission. IEEE Transactions on Plasma Science, 31 (6): 1263-1267
7. Wien, W.; Lummer, O., 1895: Methode zur Prüfung des Strahlungsgesetzes absolut schwarzer Körper. Annalen der Physik, 292 (11): 451-456
8. Bohr, N., 1913: On the Constitution of Atoms and Molecules. Philosophical Magazine, 26: 1-25
17. Tsintsadze, L. N.; Callebaut, D. K.; Tsintsadze, N. L., 1996: Black-body radiation in plasmas. Journal of Plasma Physics, 55: 407-413
magicjava wrote:Question 2: Does anyone know of any papers that estimate how long the sun could burn via recombination before running out of fuel?
Here is what Wikipedians had to say:
Wikipedia wrote:In the early years of the modern scientific era, the source of the Sun's energy was a significant puzzle. Lord Kelvin suggested that the Sun was a gradually cooling liquid body that was radiating an internal store of heat. Kelvin and Hermann von Helmholtz then proposed a gravitational contraction mechanism to explain the energy output. Unfortunately the resulting age estimate was only 20 million years, well short of the time span of at least 300 million years suggested by some geological discoveries of that time. In 1890 Joseph Lockyer, who discovered helium in the solar spectrum, proposed a meteoritic hypothesis for the formation and evolution of the Sun.
153. Thomson, W. (1862). "On the Age of the Sun's Heat". Macmillan's Magazine 5: 388–393.
154. Lockyer, J.N. (1890). The meteoritic hypothesis; a statement of the results of a spectroscopic inquiry into the origin of cosmical systems. Macmillan and Co.