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Photon excitation of sodium emission in Comets


We consider the possibility of the excitation of sodium resonance emission in cometary matter under solar radiation at a heliocentric distance of 5 AU, as was observed when a fragment of Comet Shoemaker-Levy 9 plunged into Jupiter. When the sodium emission is calculated, the multiple scattering in the cometary cloud is taken into account. We use a non-LTE radiative transfer code for a two-level model sodium atom. A comparison of the computed and observed Na I D emission line profiles allows the column density of the sodium atoms for specific times of observations of Comet Shoemaker-Levy 9 to be determined. The observed Na I(D1+D2) line profile was found to agree well with the computed profile for an optically thick sodium cloud. We calculated the column density of the sodium atoms for three comets from the observed intensity of the D2 line emission. We also calculated the D2/D1 intensity ratio for various optical depths of the sodium cloud and various phase angles.

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Translated from Pis'ma v Astronomicheski\(\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{l}\) Zhurnal, Vol. 30, No. 11, 2004, pp. 874–880.

Original Russian Text Copyright © 2004 by Baranovsky, Tarashchuk.

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Baranovsky, E.A., Tarashchuk, V.P. Photon excitation of sodium emission in Comets. Astron. Lett. 30, 797–802 (2004).

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Key words

  • Solar system—planets
  • comets
  • small bodies
  • heliosphere
  • sodium emission
  • radiative transfer
  • light scattering