Structure and Composition of the Solar System

A set of question-and-answer flashcards covering the formation, structure, and key regions of the solar system as discussed in the lecture notes.

Around how many years ago did the solar system form?

Approximately 4.5 billion years ago.

What collapsing material gave rise to the solar system?

A cloud of interstellar gas and dust.

In which spiral arm of the Milky Way is our solar system located?

The Orion Arm.

What are the two main categories of planets in our solar system?

Terrestrial planets and Jovian planets.

Which planets are classified as terrestrial planets?

Mercury, Venus, Earth, and Mars.

Give two key characteristics shared by terrestrial planets.

They have rocky, solid surfaces and lack ring systems (they also possess few or no moons and are relatively small and dense).

Where are the Jovian planets located relative to the asteroid belt?

Beyond the asteroid belt.

What two sub-groups make up the Jovian planets?

Gas giants and ice giants.

Which planets are considered gas giants?

Jupiter and Saturn.

Which planets are considered ice giants?

Uranus and Neptune.

How do ice giants differ compositionally from gas giants?

Ice giants contain hydrogen, helium, and larger amounts of water, methane, and ammonia, while gas giants are mostly hydrogen and helium.

Where is the asteroid belt located, and what does it contain?

Between Mars and Jupiter; it contains rocky debris that never formed into a planet.

What is the Kuiper Belt and why is it important?

A region beyond Neptune filled with icy bodies and dwarf planets; it is the source of many short-period comets.

Describe the Oort Cloud.

A hypothetical spherical shell of icy objects surrounding the solar system, thought to be the source of long-period comets and marking the Sun’s gravitational boundary.

Define an astronomical unit (AU).

The average Earth–Sun distance, about 93 million miles (150 million kilometers).

What is the heliosphere?

A vast protective bubble created by the solar wind that surrounds the solar system and shields it from much interstellar radiation.

What is the termination shock and at roughly what distance does it occur?

The region where the solar wind slows abruptly due to interstellar pressure, occurring around 80–100 AU from the Sun.