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Table of Contents Enchanted Learning
All About Astronomy
Site Index
Our Solar System Stars Glossary Printables, Worksheets, and Activities
The Sun The Planets The Moon Asteroids Kuiper Belt Comets Meteors Astronomers

Your weight on the Planets The Planets Your age on the Planets
Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune pluto

The Planets (plus the Dwarf Planet Pluto)

Our solar system consists of the sun, eight planets, moons, many dwarf planets (or plutoids), an asteroid belt, comets, meteors, and others. The sun is the center of our solar system; the planets, their moons, a belt of asteroids, comets, and other rocks and gas orbit the sun.

The eight planets that orbit the sun are (in order from the sun): Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Another large body is Pluto, now classified as a dwarf planet or plutoid. A belt of asteroids (minor planets made of rock and metal) lies between Mars and Jupiter. These objects all orbit the sun in roughly circular orbits that lie in the same plane, the ecliptic (Pluto is an exception; it has an elliptical orbit tilted over 17° from the ecliptic).

Easy ways to remember the order of the planets (plus Pluto) are the mnemonics: "My Very Excellent Mother Just Sent Us Nine Pizzas" and "My Very Easy Method Just Simplifies Us Naming Planets" The first letter of each of these words represents a planet - in the correct order.

The largest planet is Jupiter. It is followed by Saturn, Uranus, Neptune, Earth, Venus, Mars, Mercury, and finally, tiny Pluto (the largest of the dwarf planets). Jupiter is so big that all the other planets could fit inside it.

The Inner Planets vs. the Outer Planets
The inner planets (those planets that orbit close to the sun) are quite different from the outer planets (those planets that orbit far from the sun).
Temperatures on the Planets
Generally, the farther from the Sun, the cooler the planet. Differences occur when the greenhouse effect warms a planet (like Venus) surrounded by a thick atmosphere.

Density of the Planets
The outer, gaseous planets are much less dense than the inner, rocky planets.

The Earth is the densest planet. Saturn is the least dense planet; it would float on water.

The Mass of the Planets
Jupiter is by far the most massive planet; Saturn trails it. Uranus, Neptune, Earth, Venus, Mars, and Pluto are orders of magnitude less massive.

Gravitational Forces on the Planets
The planet with the strongest gravitational attraction at its surface is Jupiter. Although Saturn, Uranus, and Neptune are also very massive planets, their gravitational forces are about the same as Earth. This is because the gravitational force a planet exerts upon an object at the planet's surface is proportional to its mass and to the inverse of the planet's radius squared.

A Day on Each of the Planets
A day is the length of time that it takes a planet to rotate on its axis (360°). A day on Earth takes almost 24 hours.

The planet with the longest day is Venus; a day on Venus takes 243 Earth days. (A day on Venus is longer than its year; a year on Venus takes only 224.7 Earth days).

The planet with the shortest day is Jupiter; a day on Jupiter only takes 9.8 Earth hours! When you observe Jupiter from Earth, you can see some of its features change.

The Average Orbital Speed of the Planets
As the planets orbit the Sun, they travel at different speeds. Each planet speeds up when it is nearer the Sun and travels more slowly when it is far from the Sun (this is Kepler's Second Law of Planetary Motion).

The Planets in Our Solar System
Planet (or Dwarf Planet) Distance from the Sun
(Astronomical Units
Period of Revolution Around the Sun
(1 planetary year)
Period of Rotation
(1 planetary day)
Apparent size
from Earth
Range or Average)
Number of Moons
Mercury 0.39 AU, 36 million miles
57.9 million km
87.96 Earth days 58.7 Earth days 3.3 x 1023 3,031 miles
4,878 km
5-13 arc seconds 100-700 K
mean=452 K
Venus 0.723 AU
67.2 million miles
108.2 million km
224.68 Earth days 243 Earth days 4.87 x 1024 7,521 miles
12,104 km
10-64 arc seconds 726 K 0
Earth 1 AU
93 million miles
149.6 million km
365.26 days 24 hours 5.98 x 1024 7,926 miles
12,756 km
Not Applicable 260-310 K 1
Mars 1.524 AU
141.6 million miles
227.9 million km
686.98 Earth days 24.6 Earth hours
=1.026 Earth days
6.42 x 1023 4,222 miles
6,787 km
4-25 arc seconds 150-310 K 2
Jupiter 5.203 AU
483.6 million miles
778.3 million km
11.862 Earth years 9.84 Earth hours 1.90 x 1027 88,729 miles
142,796 km
31-48 arc seconds 120 K
(cloud tops)
67 (18 named plus many smaller ones)
Saturn 9.539 AU
886.7 million miles
1,427.0 million km
29.456 Earth years 10.2 Earth hours 5.69 x 1026 74,600 miles
120,660 km
15-21 arc seconds
excluding rings
88 K 62 (30 unnamed)
Uranus 19.18 AU
1,784.0 million miles
2,871.0 million km
84.07 Earth years 17.9 Earth hours 8.68 x 1025 32,600 miles
51,118 km
3-4 arc seconds 59 K 27 (6 unnamed)
Neptune 30.06 AU
2,794.4 million miles
4,497.1 million km
164.81 Earth years 19.1 Earth hours 1.02 x 1026 30,200 miles
48,600 km
2.5 arc seconds 48 K 13
Pluto (a dwarf planet) 39.53 AU
3,674.5 million miles
5,913 million km
247.7 years 6.39 Earth days 1.29 x 1022 1,413 miles
2,274 km
0.04 arc seconds 37 K 4
Planet (or Dwarf Planet) Distance from the Sun
(Astronomical Units
Period of Revolution Around the Sun
(1 planetary year)
Period of Rotation
(1 planetary day)
Apparent size
from Earth
Range or Average)
Number of Moons

Another Planet?
In 2005, a large object beyond Pluto was observed in the Kuiper belt.

A few astronomers think that there might be another planet or companion star orbiting the Sun far beyond the orbit of Pluto. This distant planet/companion star may or may not exist. The hypothesized origin of this hypothetical object is that a celestial object, perhaps a hard-to-detect cool, brown dwarf star (called Nemesis), was captured by the Sun's gravitational field. This planet is hypothesized to exist because of the unexplained clumping of some long-period comet's orbits. The orbits of these far-reaching comets seem to be affected by the gravitational pull of a distant, Sun-orbiting object.

Planet Activities and Quizzes
Planet Coloring pages

An interactive puzzle on the Solar System.

Find It!, a quiz on the planets.

A fill-in-the-blank (cloze) activity on the Solar System - or go to the answers.

Solar System Model to make.

Solar System calendar to print out and color.

Solar System Crafts

How to write a report on a planet - plus a rubric.


Astronomy: K-3 Theme Page

Activities, quizzes, books to print, and printouts.

The Planets
A Book With Tabs

An activity book on the Solar System to print for fluent readers. The book contains information, pictures, and questions to answer.

The Solar System Book

A simple printable coloring book about the Solar System to print (for early readers). Pages on the Solar System, the sun, Mercury, Venus, the Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.
Solar System Coloring Book

Color and learn about our Solar System, the Sun, the planets, asteroids, comets, and our moon.

Solar System Diagram

Label the Sun and planets.

Earth's Atmosphere

Label the atmospheric layers of the Earth.

Earth Diagram

Label the inside of the Earth.

Celsius Bar Graph Questions #2:
Printable Worksheet

A printable activity worksheet in which the student reads a bar graph of the average temperatures of the planets to answer questions, for example, "On average, is it warmer on Jupiter or Mars?" Or go to the answers. Go to a pdf version of the worksheet.

Moon Phases Diagram

Label the phases of the waxing and waning moon.

Lunar Eclipse Diagram

Label the lunar eclipse.

Planet-Sun Orbital Diagram

Label the aphelion (farthest point in orbit) and perihelion (closest point in orbit) of a planet in orbit.
Alphabetical Order

Put 10 Planet Words in Alphabetical Order - Worksheet

Put 10 planet words in alphabetical order. The words are: Earth, Jupiter, Mars, Mercury, moon, Neptune, Pluto, Saturn, Uranus, Venus. Go to the answers.
Planets to label

The Planets in English
A Label Me! Printout

Label the Solar System in English.
Planets to label

The Planets in French
A Label Me! Printout

Label the Solar System in French.
Planets to label

The Planets in German
A Label Me! Printout

Label the Solar System in German.
Planets to label

The Planets in Italian
A Label Me! Printout

Label the Solar System in Italian.
Planets to label

The Planets in Portuguese

Label the planets in Portuguese.
Planets to label

The Planets in Spanish
A Label Me! Printout

Label the Solar System in Spanish.

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