Download The Modern Solar System

Planetary Configurations and Phases
The Modern Solar System
 The planets of the modern solar system are grouped into several different and
sometimes overlapping classifications:
 The planets inside the orbit of the earth are called the Inferior Planets: Mercury and
Venus.
 The planets outside the orbit of the earth are called the Superior Planets: Mars,
Jupiter, Saturn, Uranus, Neptune, and Pluto.
 The planets inside the asteroid belt are termed the Inner Planets (or the Terrestrial
Planets): Mercury, Venus, Earth, and Mars.
 The planets outside the asteroid belt are termed the Outer Planets: Jupiter, Saturn,
Uranus, Neptune, and Pluto.
 The planets sharing the gaseous structure of Jupiter are termed the Gas Giant (or
Jovian) Planets: Jupiter, Saturn, Uranus, and Neptune.
Configurations
 Location of the planet with respect to the celestial
sphere
 Conjunction – when a planet is at the same
longitude along the sun's path (in line with the Sun)
 Opposition – when a planet makes an angle of 1800
from the Sun as viewed from the Earth (opposite
direction from the Sun)
 Quadrature - when a planet makes an angle with the
Sun of 900 when viewed from Earth (right angle with
the Sun)
 Greatest Elongation - the largest separation of the
planet from the Sun in our sky, either to the East, or
to the West
Superior vs. Inferior Planets
 The configurations and phases of the superior and
inferior planets differ because of geometry:
o Superior = orbits are outside that of the Earth
o Inferior = orbits are between the Earth and the
Sun
 The superior planets do not exhibit a full range of
phases; they are always gibbous or full.
 The superior planets can be located at any distance
East (left) or West (right) of the Sun in our sky, unlike
the inferior planets where there is a limiting angle
away from the Sun (greatest elongation).