Jupiter’s innards are full of the remains of baby planets that the gas giant gobbled up as it expanded into the behemoth we see today, scientists have found. The results come from the first clear look at the chemistry beneath the planet’s murky outer atmosphere.
Despite being the largest planet in the solar system, Jupiter has revealed very little about its inner workings. Telescopes have captured thousands of images of it swirling vortex clouds in the gas giant’s upper atmosphere, but these Van Gogh-like storms also act as a barrier, blocking our view of what lies below.
“Jupiter was one of the first planets to form in ours solar systemlead researcher Yamila Miguel, an astrophysicist at Leiden University in the Netherlands, told Live Science in the first few million years after the solar system took shape about 4.5 billion years ago. However, we know almost nothing specific about how it formed, she added.
Related: “Baby Jupiter” was discovered in formation around a star 500 light-years away
In the new study, researchers were finally able to peer past Jupiter’s opaque cloud cover using gravitational data collected by NASA’s Juno spacecraft. This data allowed the team to map the rocky material at the giant planet’s core, which revealed a surprisingly high abundance of heavy elements. The chemical composition suggests that Jupiter has been engulfing baby planets, or planetesimals, to fuel its expansive growth.
Growing gas giant
Jupiter may be mostly a ball of swirling gas today, but it began life accumulating rocky material just like every other planet in the solar system. Like those of the planet heaviness As more rock was pulled in, the rock core became so dense that it began sucking in large amounts of gas from great distances—mainly hydrogen and helium, released from the Sun‘s birth – to form its enormous gas-filled atmosphere.
There are two competing theories as to how Jupiter managed to collect its initial rock material. One theory has it that Jupiter has accumulated billions of smaller space rocks that astronomers refer to as pebbles (although these rocks are likely more like boulders than true pebbles in size).
The opposite theory, supported by the new study’s findings, says Jupiter’s core formed through the absorption of many planetesimals – large space rocks stretching several miles that, if left undisturbed, could potentially serve as seeds for smaller ones rocky planets could have served as Earth or Mars might evolve.
So far, however, it has not been possible to say with certainty which of these theories is correct. “Since we can’t directly observe the formation of Jupiter, we need to put the pieces together with the information we have today,” Miguel said. “And that’s no easy task.”
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exploration of the planet
To settle the debate, researchers needed to create an image of Jupiter’s interior. “Here on Earth, we use seismographs to study the interior of the planet based on earthquakes,” Miguel said. But Jupiter doesn’t have a surface to attach such devices to, and Jupiter’s core likely won’t see much tectonic activity anyway, she added.
Instead, the researchers built computer models of Jupiter’s innards by combining data collected mostly from Juno and some data from its predecessor, Galileo. The probes measured the planet’s gravitational field at various points in its orbit. The data showed that rock material accumulated by Jupiter has a high concentration of heavy elements, which form dense solids and therefore have a stronger gravitational pull than the gaseous atmosphere. This data allowed the team to map slight fluctuations in the planet’s gravity, which helped them see where the rocky material is located within the planet.
“Juno provided very accurate gravitational data that helped us constrain the distribution of material inside Jupiter,” said Miguel. “It’s very unique data that we can only get from a spacecraft orbiting the planet.”
The researcher’s models showed that there is an equivalent of 11 to 30 Earth masses of heavy elements in Jupiter (3% to 9% of Jupiter’s mass), which is much more than expected.
Pebbles vs Planetesimals
The new models point to a planetesimal engulfing origin for Jupiter because pebble accretion theory can’t explain such a high concentration of heavy elements, Miguel said. If Jupiter originally formed from pebbles, the eventual start of the gas accretion process once the planet was large enough would have ended the rocky accretion phase immediately. This is because the growing layer of gas would have created a pressure barrier that would have prevented more pebbles from being pulled into the planet, Miguel explained. This shortened rocky accretion phase would likely have given Jupiter a much reduced heavy metal abundance, or metallicity, than the researchers calculated.
However, planetesimals could also have smoldered on Jupiter’s core after the start of the gas accretion phase; Because the gravitational pull on the rocks would have been greater than the gas pressure. This simultaneous accretion of rocky material and gas, suggested by the planetesimal theory, is the only explanation for the high concentrations of heavy elements in Jupiter, the researchers said.
The study also revealed another interesting finding: Jupiter’s interior does not mix well with its upper atmosphere, contrary to scientists’ expectations. The new model of Jupiter’s interior shows that the heavy elements the planet absorbed have largely stayed near its core and lower atmosphere. Researchers had hypothesized that convection was churning Jupiter’s atmosphere so that hotter gas near the planet’s core would rise into the outer atmosphere before cooling and falling back down; If this were the case, the heavy elements would be mixed more evenly in the atmosphere.
However, it’s possible that certain regions of Jupiter have a small convection effect, and more research is needed to determine exactly what’s going on in the gas giant’s atmosphere, Miguel said.
The researchers’ findings could also change the formation histories for other planets in the solar system. “Jupiter was the most influential planet in the formation of the solar system,” said Miguel. Its gravitational pull helped shape the size and orbits of its cosmic neighbors, and so determining how it formed has important implications for other planets, she added. The results also point to a possible planetesimal origin for the other gas giants in the solar system: Saturn, Uranus and Neptune.
Other gaseous worlds in other star systems may also have formed by devouring planetesimals rather than pebbles, meaning they may also have higher metallicity than their appearance suggests. It is therefore important that we find these new worlds that are being searched for with the help of NASA James Webb Telescopewe don’t judge them by their cloudy covers, the researchers said.
The study was published online June 8 in the journal astronomy and astrophysics (opens in new tab).
Originally published on Live Science.
https://www.livescience.com/jupiter-ate-baby-planets-while-growing Baby Jupiter got so big by eating other baby planets