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Io, the closest Galileo's Medicean Moon: Changes in its Sodium Cloud Caused by Jupiter Eclipse

Published online by Cambridge University Press:  03 November 2010

Cesare Grava ,
Nicholas M. Schneider  and
Cesare Barbieri
Cesare Grava
Affiliation:
Department of Astronomy, Padova University, Vicolo dell' Osservatorio, 3, 35122 Padova, Italy email: [email protected], [email protected]
Nicholas M. Schneider
Affiliation:
LASP, University of Colorado Campus Box 392, Boulder, Colorado 80309-0392515, USA email: [email protected]
Cesare Barbieri
Affiliation:
Department of Astronomy, Padova University, Vicolo dell' Osservatorio, 3, 35122 Padova, Italy email: [email protected], [email protected]
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Abstract

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We report results of a study of true temporal variations in Io's sodium cloud before and after eclipse by Jupiter. The eclipse geometry is important because there is a hypothesis that the atmosphere partially condenses when the satellite enters the Jupiter's shadow, preventing sodium from being released to the cloud in the hours immediately after the reappearance. The challenge lies in disentangling true variations in sodium content from the changing strength of resonant scattering due Io's changing Doppler shift in the solar sodium absorption line. We undertook some observing runs at Telescopio Nazionale Galileo (TNG) at La Palma Canary Island with the high resolution spectrograph SARG in order to observe Io entering into Jupiter's shadow and coming out from it. The particular configuration chosen for the observations allowed us to observe Io far enough from Jupiter and to disentangle line-of-sight effects looking perpendicularly at the sodium cloud. We will present results which took advantage of a very careful reduction strategy. We remove the dependence from γ-factor, which is the fraction of solar light available for resonant scattering, in order to remove the dependence on the radial velocity of Io with respect to the Sun.

This work has been supported by NSF's Planetary Astronomy Program, INAF/TNG and the Department of Astronomy and Cisas of University of Padova, through a contract by the Italian Space Agency ASI.

Keywords

Planets and satellites: Io
Type
Poster Papers
Information
Proceedings of the International Astronomical Union , Volume 6 , Symposium S269: Galileo's Medicean Moons: their impact on 400 years of discovery , January 2010 , pp. 224 - 228
Copyright
Copyright © International Astronomical Union 2010

References

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