The Theory of Nothing

What's inside Jupiter?

What's inside Jupiter?

Everyone knows that Jupiter is the largest planet in the solar system. It may be large but its mass is one thousandth that of the Sun. Jupiter's equatorial radius is 71,483 kilometers or 11,209 Earths. Its polar radius is 66,854 kilometers, which means that it has an oblate shape because of its rapid rotational period (just under 10 hours). Jupiter is 2.5 times the mass of all of the other planets in the solar system combined. Yeah, that's big. It's large enough to have 67 moons orbiting it.

Jupiter is considered a gas giant, which means that it's composed of mostly gas and liquid. One could think of Jupiter as a dwarf star that never made it to ignition because it's not big enough. Jupiter's atmosphere has roughly 75% hydrogen and 24% helium so it's like a star. Much like stars, Jupiter's atmosphere has trace amounts of stuff like carbon, ethane, benzene, neon, oxygen, phosphorus and sulfur. The other gas giants like Saturn have a similar atmospheric composition but Uranus and Neptune have much less hydrogen and helium in their atmospheres.

Gas giants are not nearly as dense as rocky planets. Saturn has a density less than that of water and would actually float on water, if one could find an ocean large enough to hold it. Their massive gravity is because of their immense sizes.

The big question is: what's inside Jupiter? This is a question that astronomers have been trying to answer for a long time. As you could imagine, this is a difficult question to answer because of the fact that it's nearly impossible to send a probe deep into the atmosphere of Jupiter. A probe was sent down into Jupiter's atmosphere on December 7, 1995. It penetrated 150 kilometers and lasted for nearly 58 minutes before being crushed. Since Jupiter's atmosphere is over 5000 kilometers thick, this was only a tiny prick of what's really down there.

Jupiter has a 50-kilometer deep cloud layer. The clouds consist of ammonia crystals and other compounds of ammonia. Everyone is familiar with the Great Red Spot, which is a humongous cyclone (actually it's anticyclonic because it rotates counter clockwise) storm that has been raging for centuries. Two or three Earths could fit into it. There are many other smaller storms in Jupiter's turbulent atmosphere.

From various planetary probes, scientists have formulated a theory as to what's inside Jupiter. As one goes down through the 50 kilometer cloud layer and gets rained on with liquid helium and neon, one gets to a more liquid hydrogen layer that extends for hundreds of kilometers before one runs into a metallic hydrogen layer that extends down for two or three thousand kilometers. This metallic hydrogen layer extends out about 78% of the radius of the planet and covers the core.

What the heck is metallic hydrogen? This is a phase of hydrogen in which it becomes an electrical conductor. The pressure and temperature (67 C) to achieve this phase of hydrogen is very high, on the order of 3.5 million pounds per square inch. Metallic hydrogen is thought to be liquid rather than solid, but this not well understood.

It's thought that rain droplets of liquid helium and neon fall down through this massive layer of metallic hydrogen. I'm not sure how that works.

The internal core of Jupiter is thought to be composed of ice and rock. It's hard to imagine what that would look like under the intense pressure that exists there. One thing we do know is that Jupiter has a huge magnetosphere that's as strong as Earth's. This is thought to be due to eddy currents consisting of conducting material. It's probably caused by the rotation of metallic hydrogen directly above the core. Rotation of molten iron above the solid core is what causes Earth's magnetosphere.

Another problem with understanding Jupiter's core is the fact that the temperature increases rapidly as one goes down through the planet's atmosphere and outer core. At the metallic hydrogen layer it's believed to be 10,000 K and at the core boundary it could be as high as 30,000 K. The pressure at this point is outrageously high. No known probe material could exist under these conditions.

As you can see from this, the true nature of what's inside Jupiter is not well known. Most of it is based on theories. Maybe someday, we'll know for sure, but for now, I think it's best to consider Jupiter as a mysterious and beautiful object in the sky.

Thanks for reading.