Bibcode
Sainz Dalda, A.; Doressoundiram, A.; Cremonese, G.; López Ariste, A.; Fulle, M.; Leblanc, F.; Gelly, B.
Bibliographical reference
Astronomy and Astrophysics, Volume 482, Issue 1, 2008, pp.293-298
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4
2008
Journal
Citations
12
Refereed citations
11
Description
Comet McNaught C/2006 P1 was the brightest comet of the last forty years
when reaching its perihelion at an heliocentric distance of 0.17Â
AU. Two days before this perihelion, at an heliocentric distance of
0.2Â AU, Themis, a French-Italian solar telescope in the Canary
Islands, Spain, observed the Comet sodium emission of McNaught. The
measured maximum sodium brightness of the D2Â emission line peaked
at 900Â Mega-Rayleigh. The spatial distribution of the sodium
emission with respect to the nucleus of the comet is in agreement with
previous observations. It displays a clear sunward-tailward asymmetry
that suggests a dichotomy of the sodium sources between a source close
to the nucleus and an extended source most probably corresponding to the
dust tail. The spatial distribution along the slit of the width and
speed of the Doppler Na distribution also suggests such a
dichotomy. The sodium ejection rate inferred from this observation
agrees with the value of the ejection rate extrapolated from comet
Hale-Bopp, taking into account the heliocentric distance of comet
McNaught and its significantly larger dust release. If we suppose a
similar concentration of sodium atoms in both comets, this observation
suggests that the sodium ejection rate from comets McNaught and
Hale-Bopp is proportional to the solar flux. Therefore the most probable
ejection mechanisms are photo-sputtering, solar wind sputtering, or
cometary ion sputtering, and not thermal desorption.
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