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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 Inner Planets vs. the Outer Planets

The inner planets are: Mercury, Venus, Earth, and Mars. They are relatively small, composed mostly of rock, and have few or no moons.

The outer planets include: Jupiter, Saturn, Uranus, Neptune, and Pluto (a dwarf planet). They are mostly huge, mostly gaseous, ringed, and have many moons (again, the exception is Pluto, the dwarf planet, which is small, rocky, and has four moons).

Temperatures on the Planets

Density of the Planets

The Mass of the Planets

Gravitational Forces on the Planets

A Day on Each of the Planets

The Average Orbital Speed of the Planets

The Planets in Our Solar System

Planet (or Dwarf Planet) Distance from the Sun

(Astronomical Units

miles

km) Period of Revolution Around the Sun

(1 planetary year) Period of Rotation

(1 planetary day) Mass

(kg) Diameter

(miles

km) Apparent size

from Earth Temperature

(K

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 10 23 3,031 miles

4,878 km 5-13 arc seconds 100-700 K

mean=452 K 0 Venus 0.723 AU

67.2 million miles

108.2 million km 224.68 Earth days 243 Earth days 4.87 x 10 24 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 10 24 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 10 23 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 10 27 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 10 26 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 10 25 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 10 26 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 10 22 1,413 miles

2,274 km 0.04 arc seconds 37 K 4 Planet (or Dwarf Planet) Distance from the Sun

(Astronomical Units

miles

km) Period of Revolution Around the Sun

(1 planetary year) Period of Rotation

(1 planetary day) Mass

(kg) Diameter

(miles

km) Apparent size

from Earth Temperature

(K

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.

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