Astronomy 67 - The Solar System - Terrestrial vs Jovian - Part 4

Overview

This lecture discusses the composition and structure of Jovian (gas giant) planets, comparing them to Earth and explaining why they are not considered "mostly solid."

Jovian Planets: Composition and Structure

• Jovian planets are also called gas giants, but this name can be misleading.
• They are not mostly solid, but do contain solid material.
• Each Jovian planet has a dense, rocky core made of rock and metal.
• The rocky core of Jupiter is larger and more massive than Earth itself.
• Despite having more solid material than Earth, Jovian planets have much more gas and liquid above their cores.
• The predominant components of the outer layers are gas and liquid, not solid.

Comparing Interiors: Jovian Planets vs. Earth

• Earth's mass is almost entirely solid or liquid, so it is considered "mostly solid."
• Jovian planets have a significant rocky core, but the immense amount of gas and liquid makes them not "mostly solid."
• The "solid" component is less noticeable due to the sheer abundance of gas and liquid.

Oceans on Earth and Jovian Planets

• Earth's oceans are a tiny, thin surface layer compared to the size of the planet.
• Jupiter's "ocean" (liquid layer) is thousands of times deeper than Earth's oceans.
• The liquid layer in Jovian planets could "cover" multiple Earths stacked atop each other.

Composition of Jovian Oceans

• Jovian planet oceans are not made of water but of hydrogen and helium.
• The hydrogen and helium oceans are composed of liquid forms of these elements, not gases.
• These elements are the most common in the universe and compose both the Sun and Jovian planets.

Key Terms & Definitions

• Jovian Planets (Gas Giants) — Large planets with thick atmospheres of hydrogen and helium and relatively small rocky cores.
• Rocky Core — Dense, central region made of rock and metal inside a planet.
• Hydrogen and Helium Oceans — Deep liquid layers in Jovian planets, made mostly of hydrogen and helium, not water.

Action Items / Next Steps

• Review the structure and composition of Jovian planets.
• Understand the differences between terrestrial and Jovian planets for upcoming discussions or exams.