The Fuzziness of Giant Planets’ Cores

Giant planets are thought to have cores in their deep interiors, and the division into a heavyelement core and hydrogen–helium envelope is applied in both formation and structure models. We show that the primordial internal structure depends on the planetary growth rate, in particular, the ratio of heavy elements accretion to gas accretion. For a wide range of likely conditions, this ratio is in one-to-one correspondence with the resulting post-accretion profile of heavy elements within the planet. This flux ratio depends sensitively on the assumed solid-surface density in the surrounding nebula. We suggest that giant planets’ cores might not be distinct from the envelope and includes some hydrogen and helium, and the deep interior can have a gradual heavy-element structure. Accordingly, Jupiter’s core may not be well defined. Accurate measurements of Jupiter’s gravitational field by Juno could put constraints on Jupiter’s core mass. However, as we suggest here, the definition of Jupiter’s core is complex, and the core’s physical properties (mass, density) depend on the actual definition of the core and on the planet’s growth history. DOI: https://doi.org/10.3847/2041-8213/aa6d08 Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-143118 Published Version Originally published at: Helled, Ravit; Stevenson, David (2017). The fuzziness of giant planets’ cores. The Astrophysical Journal. Letters, 840(1):4. DOI: https://doi.org/10.3847/2041-8213/aa6d08 The Fuzziness of Giant Planets’ Cores Ravit Helled and David Stevenson 1 Institute for Computational Science, University of Zurich, Zurich, Switzerland 2 School of Geosciences, Tel-Aviv University, Tel Aviv, Israel 3 Division of Geological and Planetary Sciences, Caltech, Pasadena, CA, USA Received 2017 January 30; revised 2017 March 23; accepted 2017 April 4; published 2017 April 26