Jupiter Sheds Light on a Strange Planet Outside Our Solar System

 

           

Scientists have unlocked evidence that Jupiter's core has been dissolving, and the implications reach far outside of our solar system. This new data may help to explain a puzzling discovery of a strange planet outside of our solar system.  The new planet, CoRoT-20b, was announced in February, and its discoverers searched for a suitable explanation for its unusual density. Using conventional models, the astronomers calculated that the core would have to make up over half of the planet. For comparison, Jupiter's core only represents about between 3-15 percent of the planet’s total mass.

"It's a really important piece of the puzzle of trying to figure out what's going on inside giant planets," said Jonathan Fortney, a planetary scientist at the University of California Santa Cruz who was not affiliated with the research.

Conventional planetary formation theory has modeled Jupiter as a set of neat layers with a gassy outer envelope surrounding a rocky core consisting of heavier elements. But increasing evidence has indicated that the insides of gas giants like Jupiter are a messy mixture of elements without strictly defined borders.

This new research on a melting Jovian core bolsters a mixing model of gas giant planets and would provide another avenue for heavier elements to flow throughout the planet.

"People have been working on the assumption that these planets are layered because it's easier to work on this assumption," said Hugh Wilson, a planetary scientist at the University of California Berkeley and a coauthor of the new research appearing in Physical Review Letters. Although scientists had previously toyed with the idea of melting cores in large planets, nobody sat down and did the necessary calculations, said Wilson.

Scientists have to rely on calculations of Jupiter's core environment because the conditions there are far too extreme to recreate on Earth. Wilson and his UC-Berkeley colleague Burkhard Militzer used a computer program to simulate temperatures exceeding 7,000 degrees Celsius and pressures reaching 40 million times the air pressure found on Earth at sea level.

Those conditions are thought to be underestimates of the actual conditions inside Jupiter’s core. Nonetheless, the authors found that magnesium oxide -- an important compound likely found in Jupiter's core -- would liquefy and begin drifting into Jupiter's fluid upper envelope under these relatively tame conditions.

Researchers believe that similarly-sized gas giant exoplanets -- planets found outside of our solar system -- probably have similar internal structures to Jupiter. Consequently, scientists were baffled earlier this year when they found a planet with approximately the same volume as Jupiter yet four to five times more mass.

CoRoT-20b's core presented a huge problem for traditional assumptions surrounding planet formation. "It's much easier to explain the composition of this planet under a model where you have a mixed interior," said Wilson.

Even the team that discovered the planet noted that a mixing model could allow for a more palatable planet density. Wilson's simulations not only add credence to the mixing model of giant planets but also suggest that this specific exoplanet's core is probably melting just like Jupiter's.This melting may help explain why the exoplanet's heavy elements are likely stirred up and distributed throughout its volume, said Wilson.

Santa Cruz's Fortney agrees that most of the exoplanet's heavy elements likely reside in the outer envelope. Nonetheless, he expects other factors played a larger role in how the planet's interior became mixed: "It's more of a planet formation issue."

Several other events, such as two gas giants colliding together, might explain the ultra-high density of this new planet, Wilson admits. Certain processes may also limit the effectiveness of the melting and mixing process.

Liquefied parts of a gas giant's core may have trouble reaching the outer envelope due to double diffusive convection -- a process commonly found in Earth's oceans. When salty water accumulates at the bottom of the ocean, its density keeps it from mixing thoroughly with the upper layers. In a similar fashion, the heavy elements in Jupiter's core may have trouble gaining enough energy to move upward and outward.

Scientists don't know how much this hindrance will affect potential mixing inside Jupiter, and many other questions remain to be answered about the melting process.

"The next question is, 'How efficient is this process?'" said Fortney.

Researchers will have more tools to answer this question once NASA's Juno probe reaches Jupiter in 2016. With the spacecraft's instruments carefully analyzing Jupiter's composition, Wilson believes that there will be signatures of mixing and core erosion.

 

          

The Daily Galaxy via Inside Science News Service

Image courtesy of NASA/JPL

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Comments

[Matthew]

It seems with each new discovery the universe dares to challenge our limited understanding of it.

[Ez]

"People have been working on the assumption that these planets are layered because it's easier to work on this assumption"

we seem to fail at the whole 'understanding' thing:)

[SnowballSolarSystem]

True enough, we've failed at the understanding thing, perhaps because our model of the early solar system is flawed.

The cores of CoRoT-20b like Jupiter and Earth etc. may be gradually oxidizing, driving their internal heat engines which would explain another planetary mystery.

But why would the planets have originally formed chemically-reduced cores that have been unwinding ever since? Perhaps because our sun originally formed as a close binary pair that merged in a luminous red nova (LRN) at 4.568 Ga, chemically reducing the planets and creating the short-lived radionuclides of the early solar system (since multiple stars are more common than solitary stars).

In the brief red giant phase of the LRN, the sun would have swallowed the planets causing volatile depletions, including depletions of volatile oxygen. The volatile depletion of oxygen would have chemically-reduced metal oxides to their metallic elements, resulting in sinking plumes of high-density metallic iron forming the chemically-reduced metallic-iron cores of the terrestrial planets and maybe the outer planets as well. The terrestrial planets lost their volatiles in the red giant phase resulting in the 'planetary volatility trend', but Jupiter may have expanded its girth by sucking in solar plasma during the red giant phase. But the solar plasma was highly ionized which would have had the short-term effect of chemically reducing the outer layers of the gas giant, also creating sinking plumes of metallic elements similar to what happened in the terrestrial planets. Then the reverse process of reoxidizing the core from the more-highly oxidized outer layers is in continuance to the present day.

http://hillscloud.wordpress.com

[Space Posters]

Our understanding of how planets work and evolve was based on our own solar system, now as we discover more and more planets outside our system we are learning that was a wrong assumption to make.

[Jupiter]

Gas giant, that great red spot on jupiter is just amazing.
http://solarsystemwiki.org/jupiter/