Part II Assumptions & Discussion: T = [(absorptivity/emissivity)*(Energy flux/sigma)*(a/A)]^(1/4) where: Emissivity = energy ratio emitted at a temperature = compositional property. Absorptivity = energy fraction absorbed at a temperature = compositional property.
Temperature is proportional to absorptivity but proportional to the inverse of emissivity, i.e. T^(4)=k*(absorptivity/emissivity). The useful form of this law is called the Stephan-Boltzmann Law: Energy = sigma*T^4 (S-B law constant, sigma = 5.67*10^-8*Wm^-2*K^-4) That the integrated energy radiated from a black booty is proportional to the fourth power of the temperature. This "law" is useful to convert the energy hitting an object into the temperature and is really the scientific key to address your question approximately. Kirchoff's (other) Law: For a body in radiative equilibrium energy absorption = energy emission. So we consider the very plausible scenario that the meteoroid's position in orbit doesn't alter radically (it doesn't travel near light speed!) Solar energy is mainly provided for absorption in the UV-Visible range. Energy is emitted in the IR range (vibrational energy, the meteoroid doesn't emit much light energy:-). Meteoroide is spherical in shape (OK not generality, so could vary maybe 50% either way for example when a planar shaped meteoroid had verrry low rotational energy w/r to the Sun) ABSORPTIVITY = CC = 0.8, OC = 0.65, Fe-Ni = 0.80, "ideal" = 1 EMISSIVITY = CC = 0.88, OC = 0.85, weathered Fe-Ni = 0.28, "ideal" = 1 Assumed constant emissivities, but actually they vary, for example, decreasing somewhat (and then only by a square root) as the AU's increase for Iron, and a lot for Nickel, though I expect the "weathered" surface might somewhat mitigate this. The temperature of a meteoroid in space will of course depend on the latitude, depth, it's cross sectional exposure vs. overall mass distribution and distance to the Sun, just like any other non-radioactive cooled body whether in orbit or passing through. Proximamente: More Assumptions & Discussion ______________________________________________ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
