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PHYSICS & ASTRONOMY SEMINAR: Four-Layer Models of Jupiter Based on Galileo and Juno Observations
October 4 @ 1:30 pm
Determining the interior structure of planets provides key information necessary to test planet formation theories. The best planets for this kind of research are those in our solar system, such as Jupiter. The interior of stars, including the sun, were mapped using seismology – i.e. the study of pulsations through luminosity variations. However, we do not know if planets such as Jupiter have coherent oscillations that can be observed using photometry or spectroscopy. Therefore, interior models of Jupiter are currently constrained by observations of its exterior. The goal of this research is to establish interior models of Jupiter that agree with data collected by the only two satellites to orbit Jupiter: Galileo and Juno.
Launched in 1986, Galileo released a probe that dove over 150km into the gas giant’s outer atmosphere, collecting important compositional data. The probe established that the true He and heavy element mass fractions of the outer atmosphere were significantly higher than anticipated. This lead to the now traditional, two-, or three-layer interior models of Jupiter: a gaseous envelope and a solid core. The gaseous outer envelope is sometimes split into an inner and outer envelope separated by their differing chemical compositions.
Juno has been collecting gravitational observations of Jupiter. Using Doppler measurements Juno determined the Jovian gravitational moments: inconsistencies in the gravitational field. The high gravitational moments, namely J_4 to J_10 are more sensitive in the outer planet where the high values of He and heavy elements observed by the Galileo probe.
The three-layer models do not agree with both the Galileo compositional and the Juno gravitational constraints simultaneously. Therefore, Debras and Chabrier (2019) have proposed a four-layer model that does agree with both satellites.