AS101 Lesson 7

Order of planets from Sun

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune

Asteroid Belt location

Between Mars and Jupiter

Kuiper Belt location

Beyond Neptune

Oort Cloud

Far spherical cloud surrounding solar system; source of long-period comets

Comparative planetology

Studying planets by comparing them to each other

Two planet categories

Terrestrial and Jovian

Terrestrial planets

Mercury, Venus, Earth, Mars

Jovian planets

Jupiter, Saturn, Uranus, Neptune

Terrestrial characteristics

Inner planets, small, rocky, high density, few moons

Jovian characteristics

Outer planets, large, low density, gaseous/icy, many moons, rings

Common orbital direction of planets

Counterclockwise viewed from above north pole of solar system

Planetary orbits

Nearly same plane and mostly nearly circular

Most planetary rotation

Counterclockwise (Venus and Uranus exceptions)

Inner planets moons

Few or none

Outer planets moons

Many

Rings in solar system

All Jovian planets have rings

Asteroids composition

Rocky/metallic bodies

Main asteroid location

Primarily asteroid belt

Largest asteroid/Ceres

Located in asteroid belt (dwarf planet)

Comets composition

Ice mixed with dust and rock (“dirty snowballs”)

Comet sources

Kuiper Belt and Oort Cloud

Short-period comets

Usually from Kuiper Belt

Long-period comets

Usually from Oort Cloud

Comet orbit types

Usually highly elliptical; some one-time open orbits

Coma

Gas/dust cloud around comet nucleus near Sun

Comet tails

Dust tail and ion tail

Direction of comet tail

Always points away from Sun

Meteoroid

Rock in space before entering atmosphere

Meteor

Streak of light when meteoroid enters atmosphere

Meteorite

Object that reaches ground

Age of solar system

About 4.6 billion years

Five planetary characteristics

1 common motion patterns 2 two planet types 3 inner few moons outer many moons 4 asteroids/comets present 5 common age about 4.6 billion yea