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L'instrument SYMPA détecte les pulsations de Jupiter

Une équipe de chercheurs français est parvenue, grâce à un appareil d'observation dédié, à détecter les micro-pulsations affectant l'atmosphère de Jupiter, reflets de son activité interne. Leurs résultats sont à paraître dans la revue Astronomy and Astrophysics, acceptés pour publication le 6 juin 2011.
C'est la plus grosse planète du système solaire, représentant quelques 70% de sa masse totale. Des planètes géantes, c'est elle qui a reçu le plus de visites : entre 1973 et 2007, pas moins de huit sondes spatiales l'ont observée. Et les astronomes amateurs se délectent depuis toujours de ses couleurs et de ses motifs derrière leurs télescopes ! Jupiter, pourtant, n'a pas encore lâché tous ses secrets : sa structure interne reste un mystère et les spécialistes ignorent par exemple si elle possède un noyau rocheux.

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Title: Detection of Jovian seismic waves: a new probe of its interior structure
Authors: Patrick Gaulme, François-Xavier Schmider, Jean Gay, Tristan Guillot, Cedric Jacob

Knowledge of Jupiter's deep interior would provide unique constraints on the formation of the Solar System. Measurement of its core mass and global composition would shed light on whether the planet formed by accretion or by direct gravitational collapse. At present, the inner structure of Jupiter is poorly constrained and seismology, which consists of identifying acoustic eigenmodes, offers a way to directly measure its deep sound speed profile, and thus its physical properties. Seismology of Jupiter has been considered since the mid 1970s, but hitherto the various attempts to detect global modes led, at best, to ambiguous results. We report the detection of global modes of Jupiter, based on radial velocity measurements performed with the SYMPA Fourier spectro-imager. The global seismic parameters that we measure include the frequency of maximum amplitude 1213±50 \mu Hz, the mean large frequency spacing between radial harmonics 155.3±2.2 \mu Hz and the mode maximum amplitude 49 (-10/+8) cm/s, all values that are consistent with current models of Jupiter. This result opens the way to the investigation of the inner structure of the Solar System's giant planets based on seismology techniques.

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Title: Detection of Jovian seismic waves: a new probe of its interior structure
Authors: P. Gaulme, F.-X. Schmider, J. Gay, T. Guillot, C. Jacob

No abstract available

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