Astronomy 93 - Jupiter & Saturn - Part 1 - Interiors

Overview

This lecture covers the Jovian planets, focusing on the internal structures and magnetic fields of Jupiter and Saturn, and explains the differences in their physical properties and phenomena such as aurora.

Jovian Planets Overview

• Jovian planets are Jupiter, Saturn, Uranus, and Neptune; today focuses on Jupiter and Saturn.
• Jupiter and Saturn are grouped together due to their similar compositions and structures.

Internal Structure of Jupiter and Saturn

• Both planets have four main layers: a rocky core, liquid metallic hydrogen and helium, liquid hydrogen and helium, and a gaseous hydrogen and helium atmosphere.
• The rocky core is larger than Earth and composed of materials similar to Earth, but is entirely solid due to high pressure.
• Hydrogen and helium are the dominant elements throughout all layers except the core.
• “Liquid metallic hydrogen” refers to hydrogen under extreme pressure that can conduct electricity; add “liquid” and “and helium” to the traditional layer names.
• Jupiter's immense gravity compresses more hydrogen into the metallic state than Saturn.
• Saturn has all the same layers, but has less liquid metallic hydrogen, indicating lower gravity.

Magnetic Fields of Jupiter and Saturn

• Earth’s magnetic field is generated by liquid iron in its core.
• Jupiter and Saturn lack a liquid iron core, but have strong magnetic fields produced by their liquid metallic hydrogen.
• Both planets have much stronger magnetic fields than Earth due to large amounts of conductive material.
• Jupiter has the strongest planetary magnetic field in the solar system; Saturn’s is the second strongest.

Aurora on Jupiter and Saturn

• Magnetic fields and atmospheres create auroras at the poles of Jupiter and Saturn, similar to Earth’s northern lights.
• Auroras on Jupiter and Saturn appear neon blue, unlike Earth’s, due to differences in atmospheric gases (hydrogen and helium vs. nitrogen and oxygen).

Key Terms & Definitions

• Jovian planets — gas giants composed mostly of hydrogen and helium (Jupiter, Saturn, Uranus, Neptune).
• Rocky core — central, solid region of a planet made of dense rock and metal.
• Liquid metallic hydrogen — hydrogen compressed to a state where it conducts electricity like a metal.
• Magnetic field — a region around a planet where magnetic forces are generated by conductive liquid layers.
• Aurora — light display at a planet’s poles caused by solar wind interacting with the magnetic field and atmosphere.

Action Items / Next Steps

• Review diagrams of planetary interiors, focusing on the layers of Jupiter and Saturn.
• Prepare for next lecture on Uranus and Neptune.