Cool Space Facts for Kids

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Our solar system is part of the Milky Way Galaxy and is an amazing phenomenon. Composed of eight planets, at least three dwarf planets (Pluto recently demoted from planet status), the Sun as its centre and source of power and heat, more than 130 moon satellites of planets and an immense asteroid belt. All of these bodies lie within the interplanetary medium. Distances between our planet, the third rock from the sun, Earth and other celestial bodies are immense. Humans have visited the moon but as of the present time, only monitoring devices have landed on other planets, namely Mars to gather data. Read below many cool space facts for kids that explore the crazy, strange, weird, and bizarre elements of our small section of the universe - our solar system and the planets within it.

Cool Space Facts about the Solar System

  • The Sun and all of the objects that orbit around it due to its immense gravitational pull are part of our solar system and include planets, comets, asteroids, meteoroides and moons.
  • Around 4.6 billion years ago, the solar system was formed.
  • The inner solar system consists of the Sun, Mercury, Venus, the Earth and Mars.
  • Between the orbits of Mars and Jupiter, lies the main asteroid belt.
  • The outer solar system consists of the planets Jupiter Saturn, Uranus and Neptune.
  • Because scientists recently changed their definition what makes a planet, Pluto is now classified as a dwarf planet and is part of the outer solar system.
  • The solar system is composed of mostly empty space as the planets are very tiny compared to the space between them.
  • The orbits of the planets are ellpses with the Sun.
  • All of the planets' orbits, except Mercury are nearly circular.
  • The orbits of the planets are basically in the same plane.
  • The planets all orbit in the same counter-clockwise direction looking down from above the Sun's north pole.
  • All the planets except Venus, Uranus, and the dwarf planet Pluto rotate in the same direction.
  • The terrestrial planets include Mercury, Venus, Earth, and Mars.
  • Terrestrial planets are composed mostly of rock and metal, have high densities, slow rotation, solid surfaces, no rings and few moons.
  • The jovian or gas planets include Jupiter, Saturn, Uranus and Neptune.
  • Gas planets are made up of mostly hydrogen and helium, have low densities, rapid rotation, deep atmospheres, rings and many moons.
  • The small planets with diameters of less than 13000 km include Mercury Venus, Earth, and Mars.
  • The giant planets with diameters greater than 48000 km, also known as gas giants, include Jupiter, Saturn, Uranus and Neptune.
  • Relative to Earth, Mercury and Venus are known as inferior planets because they are closer to the Sun.
  • The inferior planets show phases like our Moon when viewed from Earth.
  • Relative to Earth, the planets Mars, Jupiter, Saturn, Uranus and Neptune are superior planets because they are farther away from the Sun than Earth.
  • These superior planets always appear as full or nearly full and do not exibit phases like our Moon.
  • Mercury, Venus, Mars, Jupiter and Saturn, known as classical planets, have been known since prehistoric times because they are visible to the naked eye without the use of mechanical instruments like the telescope.
  • Modern planets, only discovered more recently with the invention of telescopes include Uranus and Neptune.
  • As of 2008, there are also five dwarf planets: Pluto, Ceres, Eris, Makemake & Haumea.
  • For thousands of years, humans believed that the Earth was the centre of the universe.
  • Astronomers including Nicolaus Copernicus, Galileo Galilei, Johannes Kepler and Isaac Newton developed a new model of our Solar System in which the planets including Earth orbit the Sun. In this heliocentric system, the Sun is the centre of our Solar System.
  • The Sun makes up 99.86 percent of the mass of our Solar System. Thus, the planets and other bodies make up a very tiny percentage of the mass.

This diagram shows the approximate relative sizes of the terrestrial planets, from left to right: Mercury, Venus, Earth and Mars. Distances are not to scale.
This diagram shows the approximate relative sizes of the terrestrial planets, from left to right: Mercury, Venus, Earth and Mars. Distances are not to scale. | Source
Jupiter, Saturn, Uranus, and Neptune are known as the jovian (Jupiter-like) planets because they are all gigantic compared with Earth, and they have a gaseous nature like Jupiter's. The jovian planets are also referred to as the gas giants, although
Jupiter, Saturn, Uranus, and Neptune are known as the jovian (Jupiter-like) planets because they are all gigantic compared with Earth, and they have a gaseous nature like Jupiter's. The jovian planets are also referred to as the gas giants, although | Source
Size of the moons of the Solar System relative to Earth.
Size of the moons of the Solar System relative to Earth. | Source

Space Facts about the Planets and Moons

Mercury:

  • It has a harsh landscape that is barren and rocky with many craters.
  • It has no air or water making it a very cold planet at night because of its inability to trap heat.
  • Its lack of atmosphere means it has very little weather or wind.
  • Because it is so close to the sun, it has extremely high day time temperature.
  • No natural satellites.
  • 57,900,000km from the sun.
  • Has a diameter of 4,878km
  • Its revolution time is 88 days which means its year is 88 days long.
  • Its rotation time is 59 days which means its day is close to the length of its year.
  • During the day, its surface temperature is 430°C while at night it dips to a frigid -170°C.
  • Density: 5.44 g/cm³
  • surface gravity relative to Earth: 0.39

Venus:

  • Harsh landscape of many craters and active volcanoes.
  • Heavy cloud cover consisting of mercury, ferric chloride hydrocarbons and sulphuric acid.
  • Because of the heavy clouds, little light reaches the surface of the planet and any light penetrating the clouds is turned into heat.
  • Atmosphere made up mostly of carbon dioxide.
  • Strong surface winds.
  • Seen in phases from Earth.
  • Sometimes called the Morning star or Evening star.
  • No natural satellites.
  • It is 108,200,000km from the sun.
  • It has a diameter of 12,100km
  • Its revolution time is 225 days which means its year is 225 days long.
  • Its rotation time is 243 days which is the length of its day which means its day is longer than its year.
  • It rotates in a direction opposite to the other planets.
  • It has a surface temperature of 470°C.
  • Density: 5.25 g/cm³
  • Gravity relative to Earth: 0.90

Earth:

  • ¼ of the surface covered by the land.
  • ¾ of the surface covered by water.
  • Atmosphere of mostly nitrogen and oxygen.
  • Supports intelligent life.
  • One natural satellite.
  • It is 149,600,000km from the sun.
  • It is 12,756km in diameter.
  • It has a revolution time of 354¼. (length of year)
  • It has a rotation time of 23.93 hours. (length of day)
  • Its surface temperature averages around 15°C.
  • Density: 5.52 g/cm³.
  • Gravity: 1.0

Mars:

  • Varied surface conditions - deserts, craters, valleys, volcanoes, great dust storms, polar ice caps.
  • It is covered with many volcanoes including the Olympus Mons, the largest volcano in our solar system. It is 21km high and is 600km across the base.
  • It is nicknamed the red planet because it is covered with rust-coloured dust.
  • Thinner atmosphere than Earth made up mostly of carbon dioxide; thus, it cannot trap much heat and is known as the 'cold planet'.
  • It has two natural satellites called Phobos and Deimos which were both discovered in 1877.
  • Distance from sun is 227,900,000km.
  • Diameter of 6,787km.
  • It has a revolution time of 68 days.
  • It has a rotations time of 24¼ hours.
  • Its surface temperature averages around -50°C.
  • Density: 3.95 g/cm³
  • Gravity relative to Earth: 0.38

Jupiter:

  • It has shifting belts of thick, colourful and poisonous gaseous clouds created by the quick spinning of the planet.
  • It has a Great Red Spot which is 38,000km in length and 10,000km in width. This spot is one of the storms raging on the planet. This red spot is a powerful hurricane which has been continual for over 300 years.
  • It has a rocky core slightly bigger than Earth's but weighing 20x more.
  • It has a 1000km deep sea of liquid hydrogen which surrounds its core.
  • It has at least 16 moons four of which are bigger than Pluto.
  • Its four main moons are named the Galilean moons (after Galileo Galilei). Their names are Io, Europa, Ganymede and Callisto.
  • 400 active volcanoes are found on Io.
  • Water may exist exist below the surface of Europa.
  • The largest moon in the solar system is Ganymede.
  • Callisto is similar in size to Mercury but is only 1/3 of its mass.
  • Distance from sun is 778,300,000km.
  • Diameter at equator 142,800km making it the largest planet in our Solar System.
  • It is so large that 1300 Earth's could fit inside it.
  • It has a revolution time of 11.86 years.
  • It has a rotation time of 9.9 hours.
  • Its atmospheric temperature is -130°C.
  • Density: 1.31 g/cm³
  • Gravity relative to Earth: 2.58

Saturn:

  • It is a stormy planet with winds raging at 800kmph.
  • The strong magnetic field traps many energy particles resulting in high radiation levels.
  • It has rings made up of ice particles ranging in size from dust to house size.
  • It is composed of a small rocky core surrounded by liquid gas.
  • Its atmosphere is made up of more hydrogen than helium giving it low density.
  • It has at least 17 moons.
  • Its largest moon is named Titan, that is the only moon known to have a dense atmosphere.
  • It is 1,427,000,000km from the sun.
  • It has a diameter of 120,400km.
  • It has a revolution time of 29.5 years.
  • It has a rotation time of 10.7 hours.
  • It has an atmospheric temperature of -185°C.
  • Density: 0.70 g/cm³
  • Gravity: 1.11

Uranus:

  • Has greenish colour with narrow rings.
  • The atmosphere is mostly hydrogen but it has a significant amount of methane which gives it the greenish colour.
  • It has a thick atmosphere of gases.
  • It rotates on a horizontal axis of about 98° from perpendicular probably due to a collision early in its formation.
  • It was the first planet discovered by telescope.
  • It rotates in a direction opposite to that of the other planets.
  • It has five natural satellites.
  • It is 2,870,000,000km from the sun.
  • It has a revolution time of 84 years.
  • It has a rotation time of about 17.3 hours.
  • It has an atmospheric temperature of -215°C.
  • Density: 1.18 g/cm³
  • Gravity relative to Earth: 1.07

Neptune:

  • Has a greenish colour.
  • It has a thick atmosphere of gases.
  • It has the most violent weather of all the planets.
  • It has freezing winds that blow ten times faster than hurricanes on Earth making it the windiest planet.
  • Neptune is the Roman god of water and this planet is a large, water planet with a blue hydrogen-methane atmosphere and faint rings.
  • It is known as the 'twin' of Uranus.
  • It has two natural satellites.
  • Triton, Neptune's largest moon, is similar in size to Earth’s moon. It was discovered in 1846 and is the seventh largest moon in the Solar System.
  • It is 4,504,000,000km from the sun.
  • It has a diameter of 48,600km.
  • It has a revolution time of 165 years.
  • It has a rotation time of 17.9 hours.
  • It has an atmospheric temperature of -200°C.
  • Density: 1.66 g/cm³
  • Gravity relative to Earth: 1.4

Test Your Solar System Knowledge

Find Your Age on Each Planet

  1. Determine your age in Earth days by multiplying your age by 365.25 (revolution time of Earth).
  2. Determine the revolution time of the planet in days if not given by multiplying the revolution time in years by 365.25.
  3. Divide your age in days by the revolution of the planet in days.

Eg. The age of a ten year old on the planet Mars:

  1. 10 years X 365.25 days/year= 3652.5 days
  2. Revolution time of Mars is 687 days.
  3. Age on Mars: 3652.5 days/year/687 days = 5.3 years

A ten year old boy or girl on Earth would be 5.3 years of age on Mars.

Your Weight in the Solar System

On which planet would your weight be the most appealing?

See results without voting

Find Your Approximate Weight on Each Planet

You can quickly find your weight on any planet by completing the following calculation:

Find your weight in pounds and multiply that number by the relative gravity on each planet.

Example: On Mercury, the gravity relative to Earth is 0.39. To determine the weight of a 150 pound person on Mercury:

Weight on Mercury=150lbs x 0.39 = 58.5lbs

Works Cited

Hipschman, Ron. Your Weight on Other Worlds. 1997.

Kid's Astronomy.com. Astronomy for Kids.

NASA. Solar System Exploration. Our Solar System: Overview. April 18, 2012.

Nine Planets. A Multimedia Tour of the Solar System: one star, eight planets, and more. 1994-2012.

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Comments 12 comments

missolive profile image

missolive 4 years ago from Texas

Wow! This is a lot of neat information! Lots of interesting facts for kids and adults alike. I'll be sure to send this to our science department as a reference for the class. Thank you for compiling this.


Teresa Coppens profile image

Teresa Coppens 4 years ago from Ontario, Canada Author

Thanks Marissa. Glad you enjoyed it and thanks so much for sharing it!


alissaroberts profile image

alissaroberts 4 years ago from Normandy, TN

What an interesting hub! I love that you included how to calculate your age and weight on each planet. In fact, I am considering moving to Mars so I can be young again ;) Fantastic job - voted up!


Teresa Coppens profile image

Teresa Coppens 4 years ago from Ontario, Canada Author

I would be so much younger on Mars too. What a great thought! Glad you enjoyed it Alissa.


Robin profile image

Robin 4 years ago from San Francisco

What an amazing resource for kids (and adults!) I wish I had this Hub when our third grader was studying planets this year. We went to the Planetarium at the San Francisco California Academy of Sciences and it was amazing. It was all about our solar system and a few of your facts were shown - very cool!


Teresa Coppens profile image

Teresa Coppens 4 years ago from Ontario, Canada Author

Thanks Robin, grade 9 Science in Ontario has a Space unit. Most kids I've taught love the material so I had a few resources to draw from. Chances are your kids will be studying Space in more detail later on. Glad you enjoyed the hub. I had fun compiling the facts and it will be easy to update at a later date!


cclitgirl profile image

cclitgirl 4 years ago from Western NC

This hub is fantastic! What a great all-in-one resource and you can even use it as a quick reference with the way this is laid-out. I learned quite a few facts. I didn't know that Mercury and Venus were "inferior" - hehe. Nice!


Teresa Coppens profile image

Teresa Coppens 4 years ago from Ontario, Canada Author

Glad you liked it Cyndi. Mercury and Venus are inferior to earth anyway he he! Thanks for the feedback!


jack 4 years ago

very cool


Teresa Coppens profile image

Teresa Coppens 4 years ago from Ontario, Canada Author

Thanks Jack


mia brown 3 years ago

i really like this web sight and i wish i was you


Teresa Coppens profile image

Teresa Coppens 3 years ago from Ontario, Canada Author

Thank you so much Mia. I'm so glad you enjoyed my hub!

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