Introduction to Planetary Systems

Astronomers use _____ of the origin of the solar system based on current observations.

• scale drawings
• experimental theories
• models
• their knowledge

Our solar system with 8 known major planets, asteroids & comets may or may not be

• as large as astronomers think it is.
• correct
• as full of gas & dust as other solar systems.
• unique

In science, all _____ can change or become modified with new discoveries.

• theories
• reality
• knowledge
• history

In our solar system, all major planets lie (roughly) in the same ____ & orbit in the same ____.

• plane, direction
• space, direction
• direction, plane
• area, space

The fact that all of the planets orbit in the same direction as the Sun rotates indicates that

• the solar system is 5 billion years old.
• they all formed at about the same time & relative space.
• there is no such thing as retrograde motion.
• Pluto may have formed somewhere else.

Which statement best describes the terrestrial planets?

• no or very few moons; solid surfaces; moderate atmospheres
• many moons; solid surfaces; extreme atmospheres
• no moons; non-solid surfaces; hot atmospheres
• they all orbit pretty close in to the Sun

Why do terrestrial planets have high densities and solid surfaces?

• because they are made of rock
• lighter elements were stripped away by the Sun
• heavier elements were blasted away by the Sun
• no one really knows

Which statement best describes Jovian or gas giant planets?

• few moons; low densities; moderate spin rates
• no moons; thick atmospheres; rapid spin rates
• many moons; thick atmospheres; rapid spin rates
• high densities; many moons; slow spin rates

Why do Jovian planets have relatively low densities?

• their spin rates are fast
• they formed relatively close to the Sun & migrated outward
• because they have many moons to make up for it
• they formed farther from the Sun & kept lighter elements

A ____ is a cloud of gas & dust that has contracted under gravity to form a star & planets.

• nebula region
• hydrogen dust field
• solar nebula
• galaxy