Structure of the Jupiter
- Low density (1300 kg/m3) implies that Jupiter is
mostly made of gas.
- Most of the universe is made of H and He, so those are the likely
candidates.
- Spectroscopy (looking at the light) by space probes gives for
the outer layers of Jupiter
- 86% H
- 14% He
- a little CH4, NH3, H2O ...
- Deep inside expect more He, less H because He is heavier.
- Measurement of infrared light emitted by Jupiter shows that
it emits twice as much energy as it gets from sun.
- This means that it is hot inside and is slowly cooling.
- It should be hot, because when the gas was compressed by
gravity it would have been heated.
- Presumably it got hot deep inside Jupiter, but not hot
enough to make it a star.
- The mass of Jupiter is about 0.001 Msun.
- But for nuclear fusion to start, a mass greater than about 0.1 Msun is needed.
- It takes a long time for something so big to cool.
- So deep inside it should be very hot and very dense.
Models give:
- pressure at center roughly 80 million atmospheres.
- temperature at center roughly 25,000 K.
- (cf surface of Sun, about 6000 K)
- Very hot and very dense hydrogen conducts electricity.
(It's "metallic")
- Jupiter has a big magnetic field.
- Recall ingredients for magnetic field (eg. on Earth)
- Heat being transfered from center.
- Fluid layer that transfers the heat by conduction.
- Rotation to bend the fluid motion.
- Fluid is electrical conductor.
- Jupiter fits all of these.
- Also, planetary scientists deduce that Jupiter has a rocky core
based on its observed oblateness.
- This is sensible from the point of view of Jupiter's evolution.
The rocky core could form first, then attract the gas.
![](model.gif)
Model for Jupiter's interior.
Note that there is no "surface of Jupiter."
ASTR 121 Home
Davison E. Soper, Institute of Theoretical Science,
University of Oregon, Eugene OR 97403 USA
soper@bovine.uoregon.edu