14 Questions
What characteristic do terrestrial planets have in common?
High densities
Which of the following is a characteristic of asteroids?
Primitive, unevolved material
What is the primary location of comets in our solar system?
The Kuiper Belt and the Oort Cloud
What suggests a high degree of order in our solar system?
The uniform ages of the components of the solar system
What is the suggested explanation for the formation of our solar system?
A single formation event 4.6 billion years ago
What has evolved over time in the solar system?
The atmospheric composition and interior structure of the planets
What is the age of the solar system, according to planetary scientists?
4.6 billion years
What is a characteristic of the planets' orbits in our solar system?
They are nearly circular
What is the direction of the planets' orbits around the Sun?
Counterclockwise as viewed from above Earth's north pole
Which of the following planets does not rotate on its axis in the same direction as the Sun's rotation?
Venus
What is the direction of most moons' orbits around their parent planet?
The same as the parent planet's rotation
What is a characteristic of our planetary system?
It is highly differentiated
Which of the following is not a characteristic of the planets in our solar system?
The planets are all identical in size and composition
What is an exception to the alignment of the planets' orbits with the Sun's equator?
Mercury
Study Notes
The Age of the Solar System
- The solar system is approximately 4.6 billion years old, based on the ages of the oldest meteorites and Earth and lunar rocks.
Key Features of the Solar System
- The planets are relatively isolated in space, with no bunching together.
- The orbits of the planets are nearly circular, with exceptions being Mercury and Pluto.
- The orbits of the planets all lie in nearly the same plane, with a few degrees of variation.
- The direction of planetary orbits and the Sun's rotation are the same, with a counterclockwise motion as viewed from above Earth's north pole.
Planetary Rotation and Moon Orbits
- Most planets rotate on their axis in the same direction as the Sun's rotation.
- Three planets (Venus, Uranus, and Pluto) do not share this property.
- Most known moons revolve about their parent planet in the same direction as the planet's rotation, except for Neptune's moon Triton.
Planetary Differentiation
- The solar system is highly differentiated, with terrestrial planets having high densities, moderate atmospheres, slow rotation rates, and few or no moons.
- Jovian planets have low densities, thick atmospheres, rapid rotation rates, and many moons.
Asteroids and Comets
- Asteroids are very old, exhibiting a range of properties not characteristic of terrestrial or jovian planets or their moons.
- Asteroids share similar bulk orbital properties with the planets but appear to be made of primitive, unevolved material.
- Comets are primitive, icy fragments that do not necessarily orbit in the ecliptic plane, primarily residing in the Kuiper Belt and the Oort Cloud.
Learn about the origins of our planetary system, from the age of the solar system to the nine known facts that shape our understanding of its architecture.
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