The Planets

The Earth's solar system is made up of the sun and the bodies that orbit around it.

These bodies include eight planets and more than 70 known moons, asteroids, comets and meteoroids, as well as interplanetary dust and gases.

There were nine planets, but Pluto is no longer officially a planet. It has been re-classified as a 'dwarf planet' because it behaves differently from the other eight planets. The eight planets are always the same distance away from the sun, unlike Pluto, which has varied distances.

Imagine a stick going through the Earth from pole to pole. This is the axis. Each planet rotates, or spins, around its axis. The time it takes to complete one rotation is one day. Each planet also orbits the sun, that is, it follows a set path to go around the sun. The time a planet takes to complete one orbit is called a year.

Information about the Planets in their order from the sun

 Planet  Diameter
(kms)
Kms from
the sun
Time to orbit sun 1 Rotation
(length of a day)
 No of Moons 
Mercury 4,850 58,000,000  88 days 58 days,
16 hours
 
NOTES:
Dry, extremely hot. Surface full of craters. To astronomers in Ancient Greece this planet was known as Apollo when seen in the morning, and Hermes when seen in the evening. The planet was later named Mercury after the Roman messenger God. The American spacecraft, Mariner 10, flew by the planet three times in 1974 and 1975. About 45 percent of the surface has been mapped.

 Planet  Diameter
(kms)
Kms from
the sun
Time to orbit sun 1 Rotation
(length of a day)
 No of Moons 
 Venus  12,100 108,000,000 225 days 243 days
 
NOTES: Surrounded by orange clouds of poisonous gas the planet is a burning desert environment. Ancient Greek astronomers called this planet Hesperus when it was seen in the morning, and Phosphorus when seen in the evening. The Romans named it Venus after the goddess of love.

 Planet  Diameter
(kms)
Kms from
the sun
Time to orbit sun 1 Rotation
(length of a day)
 No of Moons 
Earth 12,750 150,000,000 365 days  23 hours, 56 minutes 1
 
NOTES:
The only known inhabited planet, believed to be about 4000 million years old.

 Planet  Diameter
(kms)
Kms from
the sun
Time to orbit sun 1 Rotation
(length of a day)
 No of Moons 
Mars  6,880  228,000,000  687 days 24 hours, 37 minutes 2
 

NOTES: Known as the Red Planet, surface is a cold desert. Has no oceans. Has same land area as Earth. Mars is named after the Roman god of war. Its two moons are named after the horses, said to pull the god's chariot, Phobos and Deimos.

 Planet  Diameter
(kms)
Kms from
the sun
Time to orbit sun 1 Rotation
(length of a day)
 No of Moons 
Jupiter 143,000 778,000,000 12 years 9 hours, 50 minutes 67

 

NOTES: Largest planet in our solar system. Consists of gas & liquid. Has a ring around it too dark to be seen from Earth. Astronomers in Ancient Rome named the planet after the ruler of all Roman gods. Jupiter's rings were discovered by the Voyager-1 space probe in 1979. The four largest moons are Io, Europa, Ganymede and Callisto.

 Planet  Diameter
(kms)
Kms from
the sun
Time to orbit sun 1 Rotation
(length of a day)
 No of Moons 
 Saturn 120,000 1,425,000,000  30 years 10 hours, 14 minutes   62
 

NOTES: Saturn has 18 named satellites plus 12 recently discovered and as yet unnamed ones. The largest of its satellites (moons) is called Titan.Tethys (named after a Greek sea goddess) and Dione (a daughter of Zeus) Mimas, and Enceladus (son of the god Titan) are the names of four of Saturn's other moons. The planet was named in the 6th century after the Roman god of agriculture. First observed with a telescope by Galileo in 1610.

Go here for a quiz (with answers) about Saturn

 Planet  Diameter
(kms)
Kms from
the sun
Time to orbit sun 1 Rotation
(length of a day)
 No of Moons 
Uranus 51,000 2,687,000,000 84 years 20 hours ( approx) 27

 NOTES: Surrounded by clouds of blue green gas. Has 10 rings made up of dust particles. Tilts at angle, probably because of comet crashing into it. The rings adjusted their orbit and travel over and under instead of around equator. This planet was discovered by Sir william Herschell in 1781. The first of the rings were discovered in 1977.

 Planet  Diameter
(kms)
Kms from
the sun
Time to orbit sun 1 Rotation
(length of a day)
 No of Moons 
 Neptune  50,000 4,495,000,000 165 years  21 hours (approx)  13

NOTES
:  Powder blue colour, has 5 rings and at least 8 moons. Ancient astronomers calculated that there must be a planet exisiting in that place and the Romans named it after their god of the sea. It wasn't actually discovered until 1846. Voyager 2, an unmanned robot space probe photographed the five rings surrounding Neptune in 1989.


UPDATE August 2006: On August 24, 2006, the International Astronomical Union (IAU) redefined the term "planet". Because Pluto is smaller than some of the moons in our solar system and because it has an unusual orbit it is no longer recognised as one of the planets in the solar system
 Planet  Diameter
(kms)
Kms from
the sun
Time to orbit sun 1 Rotation
(length of a day)
 No of Moons 
  Pluto  2,500 5,890,000,000 248 years 6 days, 9 hours  5

 
NOTES: Smaller than Earth's moon. Astronomer Percival Lowell predicted its existence in 1916. Systematic searching followed and it was finally found by American amateur astronomer Clyde Tombaugh in 1930. The astonomical sign for the planet is made up of Lowell's initials, and so the planet was named Pluto.

Two of Pluto's moons were discovered by the Hubble Space Telescope in May 2005.


Want to remember the names and the order of the planets?
This mnemonic device is one way to help you remember the names of the planets in order from the Sun.
It uses the first letters of the planet names in a phrase.
My Very Excellent Mother Just Served Us Nachos :
Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune

For another kidcyber page about planets go here

Go here to read more about the planets:
http://www.dustbunny.com/afk/planets/
http://www.manatee.k12.fl.us/sites/elementary/samoset/psgk3ex.htm


If you use any part of this in your own work, acknowledge this source in your bibliography like this:
Thomas, R. & Sydenham, S. Planets [Online] www.kidcyber.com.au (2005)

updated May 2013 © www.kidcyber.com.au

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