# The Planets: Classification, Order, and Distance From the Sun

By Kathy Foust

How far away are the planets from the sun? Learn this and other fast facts!

## Planets in General

There are eight defined planets in the solar system, not including the Sun. Pluto has been determined to be too small to be considered a planet and so is no longer included in the formal list of planets.

How They're Classified

There are a couple of ways to classify planets. One system classifies planets as superior and inferior. Planets with smaller orbits than Earth's orbit are inferior and those with a larger orbit than Earth are called superior. Another system classifies planets as terrestrial (inner) or Jovian (outer). Terrestrial planets have similar physical and chemical characteristics as Earth's. The Jovian planets resemble Jupiter.

If the planets were to be viewed from above the North Pole on Earth, it could be seen that planets revolve counterclockwise around the Sun. A planet's distance from the Sun is measured in astronomical units (AU). An AU is the average distance from the Earth to the Sun. Therefore if a planet is 5 AU from the Sun, it would be five times as far away from the Sun as the Earth is. The formula for the measurements of an exact AU is 1.5 x 108 km or 9.3 x 107 mi. Review the section below for information on particular planets.

## Specific Planet Facts

To remember the names of the planets, use one of these simple sentences; MoVE Me JaSUN. or Mark's Voice Effects Made Jim Sound Under Nets. Use these or other anagrams that you can make up.

Below is information about each planet. Planets are placed in order of closest to the Sun, with Mercury being the closest planet to the Sun and Neptune being the furthest planet from the Sun. All measurements are calculated in relation the Earth. (Earth will always equal 1 in these measurements.)

Planet Distance from Sun Mass Diameter Inferior/Superior Terrestrial/Jovian

Sun 333,000

Mercury 0.387 AU 0.055 .38 Inferior Terrestrial

Venus 0.723 AU 0.81 0.81 Inferior Terrestrial

Earth 1.0 AU 1.0 1.0 Terrestrial

Mars 1.524 AU 0.11 0.53 Superior Terrestrial

Jupiter 5.203 AU 318 11.2 Superior Jovian

Saturn 9.529 AU 94.3 9.46 Superior Jovian

Uranus 19.19 AU 14.54 4.0 Superior Jovian

Neptune 30.06 AU 17.1 3.88 Superior Jovian

To see a planets exact distance from the Sun, use the formula for astronomical units. For instance, figure out the planet Neptune's distance from the sun. The formula is 30.06AU or 30.06(1.5 x 108km) or 30.06(9.3 x 107 mi.)

This study guide will help Physical Science students to understand some of the basic concepts about planets. These concepts will help students to understand some basic points about individual planets as well as general planetary concepts.