Jupiter consists almost exclusively of hydrogen and helium. The amounts of each correspond closely to the theoretical quantities in the original solar nebula.
But it also contains other heavier elements, which astronomers call metals. Although metals are a small part of Jupiter, their presence and distribution tell astronomers a lot.
According to a new study, Jupiter’s metal content and distribution means that the planet ate many rocky planetesimals in its youth.
Ever since NASA’s spacecraft Juno reached Jupiter in July 2016 and began collecting detailed data, it has changed our understanding of Jupiter’s formation and evolution.
The process measures Jupiter’s gravitational field and tells scientists more about the planet’s composition.
When Jupiter was formed, it began by collecting rocky material. A period of rapid gas growth from the solar nebula followed, and after many millions of years, Jupiter became the giant it is today.
But there is an important question regarding the initial period of rocky growth. Did it accredit larger masses of rocks as planetesimals? Or did it create pebble-sized material? Depending on the answer, Jupiter was formed on different time scales.
A new study intended to answer that question. It’s called “Jupiter’s inhomogeneous envelope inhomogeneous envelope“and it is published in the journal Astronomy and astrophysics. The lead author is Yamila Miguel, assistant professor of astrophysics at Leiden Observatory and the Dutch Institute for Space Research.
We’re getting used to wonderful images of Jupiter thanks to the Juno spacecraft JunoCam. But what we see is just deep skin. All these enchanting images of the clouds and storms are just the thin 50 kilometers (31 miles) outermost layer of the planet’s atmosphere.
The key to Jupiter’s formation and evolution lies deep buried in the planet’s atmosphere, which is tens of thousands of kilometers deep.
It is widely accepted that Jupiter is the oldest planet in the solar system. But researchers want to know how long it took to form. The paper’s authors wanted to investigate the metals in the planet’s atmosphere using Juno’s Gravity Science experiments.
The presence and distribution of pebbles in the planet’s atmosphere plays a central role in understanding Jupiter’s formation, and the Gravity Science experiment measured the scattering of rocks in the atmosphere.
Prior to Juno and its Gravity Science experiments, there were no exact data on Jupiter’s gravitational harmonics.
The researchers found that Jupiter’s atmosphere is not as homogeneous as previously thought. More metals are found near the center of the planet than in the other layers. In total, the metals give between 11 and 30 soil masses.
With data in hand, the team constructed models of Jupiter’s internal dynamics. “In this paper, we gather the most comprehensive and versatile collection of Jupiter’s interior models to date and use it to study the distribution of heavy elements in the planet’s envelope,” they write.
The team created two sets of models. The first set is 3-layer models and the second is dilute core models.
“There are two mechanisms for a gas giant like Jupiter to acquire metals during its formation: by accumulating small rocks or larger planetesimals.” sa lead author Miguel.
“We know that when a baby planet is large enough, it begins to push out pebbles. The richness of metals inside Jupiter that we now see is impossible to achieve before then. So we can exclude the scenario with only pebbles as solids during Jupiter’s formation. Planet decimals are too big to be blocked, so they must have played a role. “
The amount of metals in Jupiter’s interior decreases with distance from the center. This means a lack of convection in the planet’s deep atmosphere, which scientists thought was present.
“Previously we thought that Jupiter has convection, like boiling water, which makes it completely mixed,” sa Miguel. “But our findings show otherwise.”
“We strongly show that the amount of heavy elements is not homogeneous in Jupiter’s envelope,” the authors write in their newspaper. “Our results suggest that Jupiter continued to accumulate heavy elements in large quantities as its hydrogen-helium shell grew, contrary to predictions based on the rock insulation mass in its simplest incarnation, and instead favored planetesimal-based or more complex hybrid models.”
The authors also conclude that Jupiter did not mix with convection after its formation, even when it was still young and warm.
The team the results also extend to the study of gaseous exoplanets and try to determine their metallicity. “Our result … provides a base example for exoplanets: a non-homogeneous envelope means that the observed metallicity is a lower limit of the planet’s bulk metallicity.”
In Jupiter’s case, there was no way to determine its metallicity at a distance. Only when Juno came could researchers measure metallicity indirectly. “Therefore, metallicities derived from distant atmospheric observations in exoplanets may not represent the bulk metallicity of the planet.”
When the James Webb Space Telescope starts scientific activity, one of its tasks is to measure exoplanet atmospheres and determine their composition. As this work shows, the data provided by Webb may not capture what is happening in the deeper layers of giant gas planets.
#study #suggests #young #Jupiter #devoured #planetesimals