Jupiter turns out to be inhomogeneous; metallicity gives clues to origin

Credit: NASA

An international team of astronomers, led by Yamila Miguel (SRON/Leiden Observatory), has discovered that Jupiter’s gaseous envelope does not have a homogeneous distribution. The inner part contains more metals than the outer parts, totaling between 11 and 30 Earth masses, or 3 to 9 percent of Jupiter’s total mass. This is high enough metallicity to conclude that mile-sized bodies – planetesimals – must have played a role in the formation of Jupiter. It will be published on June 8 in Astronomy & Astrophysics.

When NASA’s Juno space mission arrived on Jupiter in 2016, we got a glimpse of the remarkable beauty of the largest planet in our solar system. Besides the famous Great Red Spot, Jupiter turns out to be littered with hurricanes, almost giving it the look and mystique of a Van Gogh painting. The planetary envelope below the thin visible layer is not immediately apparent, however. Yet Juno is able to paint a picture for us by detecting the gravitational pull above different locations on Jupiter. This gives astronomers information about the composition of the interior, which is unlike what we see on the surface.

An international team of astronomers, led by Yamila Miguel (SRON/Leiden Observatory), has now discovered that the gaseous envelope is not as homogeneous and well mixed as previously thought. Instead, it has a higher contraction of metals – elements heavier than hydrogen and helium – towards the center of the planet. To reach their conclusions, the team built a number of theoretical models that adhere to the observational constraints measured by Juno.

The team studied the distribution of metals because it gives them information about the formation of Jupiter. The metals turn out not to be evenly distributed in the envelope, with more in the internal part than in the external parts. The total represents between 11 and 30 earth masses of metals. Miguel: “There are two mechanisms for a gas giant like Jupiter to acquire metals during its formation: through the accretion of small pebbles or larger planetesimals. We know that once a small planet is large enough , it begins to grow pebbles. The richness of metals inside Jupiter that we now see is impossible to realize before then. We can therefore rule out the scenario with only pebbles as solids during Jupiter’s formation. Planetesimals are too big to block, so they had to play a part.

The finding that the inner part of the envelope contains more heavy elements than the outer part means that the abundance decreases outward with a gradient, instead of having homogeneous mixing across the envelope. “Previously, we thought that Jupiter had convection, like boiling water, which made it completely mixed,” explains Miguel. “But our discovery shows differently.”

A Closer Look at Jupiter’s Origin Story

More information:
Y. Miguel et al, Inhomogeneous envelope of Jupiter. arXiv:2203.01866v1 [astro-ph.EP], arxiv.org/abs/2203.01866. Accepted for publication in Astronomy & Astrophysics

Provided by SRON Netherlands Institute for Space Research

Quote: Jupiter turns out to be inhomogeneous; metallicity clues to origin (June 8, 2022) Retrieved June 8, 2022 from https://phys.org/news/2022-05-jupiter-inhomogeneous-metallicity-clues.html

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