Cremonese, G. and Huebner, W.F. and Rauer, H. and Boice, D.C. (2002) Neutral sodium tails in comets. Advances in Space Research, 29 (8), pp. 1187-1197.
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In the last few years, after a new type of tail composed only of neutral sodium atoms had been discovered in Comet Hale-Bopp, much attention has been given to the release and distribution of sodium in comets. It was not the first time that a sodium tail had been observed in a comet, but the amount af data collected from Comet Hale-Bopp in general and on the sodium emissions in particular is much larger than for any other comet. Several authors tried to identify the sources of the sodium and explain its distribution. However, no clear solution how neutram sodium atoms can be correlated with gas and dust particles has resulted. The presende of a sodium tail superimposed on the dust tail suggests a strong relation of sodium with the dust emitted by the nucleus. Furthermore, analysis of the dust data in the coma and tail provides important insights in the chemical and physical processes relevant to the dust particles. In order to investigate whether release of sodium atoms from a Na-bearing molecule may form an distributed source, we have calculated photodissociation rate coefficients (inverse lifetimes) and excess energies for several Na-bearing molecules. The calculations are based on measured cross sections near the dissociation threshold combined with cross sections at short wavelengths from the separated atom approximation for several Na-bearing molecules in the solar radiation field. Sodium can be used as a tracer of mechanisms working on other elements that are more difficult to observe. Wide interest in the sodium emissions stimulated reanalysis of wide-field images of Comet Hyakutake. It was found that this comet also had a nuetral sodium atom tail, showing that Na tails might be more common than previously thought. Our preliminary conclusion is that the sodium in the fast, narrow tail may also originate from fragmenting dust in the inner coma.
|Title:||Neutral sodium tails in comets|
|Journal or Publication Title:||Advances in Space Research|
|In ISI Web of Science:||Yes|
|Page Range:||pp. 1187-1197|
|HGF - Research field:||Aeronautics, Space and Transport (old)|
|HGF - Program:||Space (old)|
|HGF - Program Themes:||W EW - Erforschung des Weltraums|
|DLR - Research area:||Space|
|DLR - Program:||W EW - Erforschung des Weltraums|
|DLR - Research theme (Project):||UNSPECIFIED|
|Institutes and Institutions:||Institut für Weltraumsensorik und Planetenerkundung|
|Deposited By:||elib DLR-Beauftragter|
|Deposited On:||16 Sep 2005|
|Last Modified:||14 Jan 2010 19:18|
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