The Planets - Educational Astronomy Posters
for educational teaching resources in the science and social studies classrooms, homeschoolers.

A planet is generally understood to be a large object in orbit around a star, there is no scientific definition of “planet”. The ancient astronomers (observers of stars) noted how some lights moved in relation to other lights and named them “planets”- the Greek word for “wanderer”.

In this 1990 portrait gallery of the planets in the Solar System, from images made during two decades by various spacecraft from Earth, each planet appears to scale and the colors have been process for the most realistic appearance. The four giant outer gaseous planets dwarf our water-clad Earth and its three terrestrial siblings. Standing in for Pluto is an image of Meptune's moon Triton, thought to resemble the tiny planet.

1 Sun + 8 Planets + 1 Dwarf Planet + 57 Moons + 10,000 Asteroids + 100 Billion Comets

On December 16, 1999, the announcement of the first extrasolar planet to be discovered visually, 55 light years from Earth, was made. It was variously named “Tau Boo,” “Planet 2000,” or the “Millennium Planet.” It orbits close to the star Tau Bootis and is a Jupiter-like gas giant 1000 times more massive the Earth. One side of the planet always faces its star, which is somewhat more massive than our Sun. The temperature of the planet may reach 1700 C, and the planet may exhibit intense storms as its atmosphere streams from the hot day side to the cold night side. The planet may also exhibit intense aurorae and host a volcanic moon.

Uranus is the seventh planet from the sun. It is the third largest planet in the solar system.

Facts about Uranus
• Distance from the sun: 1.8 billion miles
• Diameter: 31,763 miles
• Length of year: 84 Earth years
• Rotation period/length of “day”: 17 hours, 14 minutes
• Temperature: Minus 335º Fahrenheit (average)
• Atmosphere: Hydrogen, helium, methane and small amounts of other gases
• Number of moons: 21

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Uranus, named after the ancient Greek deity of the sky, is the fourth most massive planet in the solar system.

Because it is so dim, ancient astronomers didn't recognize Uranus as a planet; it was Sir William Herschel and his sister Caroline that made Uranus the first planet discovered using a telescope in 1781.

• Uranus with 5 Moons poster

Neptune, the eighth planet from the sun, cannot be seen from Earth without a telescope.

Facts about Neptune
• Distance from the sun: 2.8 billion miles
• Diameter: 30,800 miles
• Length of year: 165 Earth years
• Rotation period/length of “day”: 16 hours and 7 minutes
• Temperature: Minus 353º Fahrenheit (average)
• Atmosphere: Hydrogen, helium, and water
• Number of moons: 13

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Neptune is the fourth largest planet by diameter in the Solar System, and the third largest by mass – Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus.

While Galileo observed Neptune in 1612, he thought it was a fixed star, so it was by astronomer Le Verrier's calculations that Neptune became the first planet discovered by mathematical prediction, 9-23-1846.

The planet Neptune is named after the Roman god of the sea and its astronomical symbol is a stylized version of Poseidon's Trident. Poseidon is the Greek name for the god of the sea; a trident, or three teeth, is three pronged spear, similar to a fisherman's ‘gig’ in the US.

Pluto, from its discovery in 1930 by astronomer Clyde W. Tombaugh until 2006, was considered the ninth planet in the Solar System. Now Pluto is classified as a dwarf planet, the largest object in the region called the Kuiper belt.

The name Pluto comes from the Roman god of the underworld, the Greek's called both their god of the underworld and the underworld, Hades. Pluto's moon Charon is named for the ferryman who carried souls of the newly deceased across the River Styx that divided the world of the living from the world of the dead.

Facts about Pluto
• Distance from the sun: 3.6 billion miles
• Diameter: 1,485 miles
• Length of year: 248 Earth years
• Rotation period/length of “day”: 6 Earth Days
• Temperature: Minus 375º Fahrenheit
• Atmosphere: Methane
• Number of moons: 1

FYI - Mickey Mouse's dog was named Pluto in honor of the discovery of the planet.

The Moon

• more moon posters