The Solar System for Kids: 40 Facts and a Scale Model You Can Make

The solar system for kids, in one sentence: it is our Sun and everything that travels around it, including eight planets, five dwarf planets, hundreds of moons and thousands of asteroids and comets. Below are 40 facts checked against NASA, a table of the planets for kids, and a scale model you can build in a park with a 20 cm ball and some beads.

Use this guide alongside our free solar system worksheets for labelling and ordering the planets, then test what your child remembers with the online solar system quiz.

Every number here comes from NASA’s Solar System Facts pages or the NASA Planetary Fact Sheet. Moon counts change as astronomers confirm new ones, so any guide like this one can go out of date; we give the figure NASA listed when we checked.

The solar system for kids: the planets at a glance

Start with the planets. The four inner planets are small and rocky. The four outer planets are giants: Jupiter and Saturn are gas giants, and Uranus and Neptune are ice giants. A handy way to remember the order is “Many Very Excited Monkeys Jump Swiftly Under Nets”.

An AU (astronomical unit) is the average distance from the Sun to Earth: about 150 million km, or 93 million miles. Neptune is about 30 AU away, so it is roughly 30 times farther from the Sun than we are.

40 solar system facts for kids

These solar system facts for kids are grouped so you can read one planet a day, and each one fits on a fact card.

The solar system as a whole

1. Our solar system has one star, eight planets, five officially recognised dwarf planets, hundreds of moons and thousands of comets and asteroids.
2. It formed about 4.6 billion years ago from a huge cloud of gas and dust.
3. The Sun holds 99.8% of all the mass in the solar system. Everything else, including all the planets, shares the last 0.2%.
4. We live in the Milky Way galaxy, in a small arm called the Orion Arm. The solar system takes about 230 million years to travel once around the centre of the galaxy.
5. In 2006 the International Astronomical Union decided a planet must orbit the Sun, be nearly round and have “cleared the neighbourhood” around its orbit. That left eight planets.

The Sun

6. The Sun is a star: a yellow dwarf made mostly of hydrogen and helium.
7. About 1.3 million Earths could fit inside it.
8. Its surface is about 5,500 °C, and its core reaches about 15 million °C.
9. Sunlight takes about 8 minutes and 20 seconds to reach Earth.
10. The nearest star after the Sun, Proxima Centauri, is 4.24 light-years away.

Mercury and Venus

11. Mercury is the smallest planet and the closest to the Sun. It is only a little larger than our Moon.
12. Mercury is the fastest planet, going round the Sun every 88 Earth days.
13. Mercury has no air to hold in heat, so days reach 430 °C and nights drop to −180 °C.
14. Venus, not Mercury, is the hottest planet: about 467 °C, hot enough to melt lead, because its thick atmosphere traps heat.
15. Venus spins backwards compared with Earth, so there the Sun would rise in the west and set in the east.
16. One spin of Venus takes 243 Earth days, which is longer than its year of 225 Earth days.
17. After the Sun and the Moon, Venus is the brightest natural object in our sky.

Earth and the Moon

18. Earth is the only place we know of with living things.
19. Earth is tilted by 23.4 degrees. This tilt, not our distance from the Sun, gives us the seasons.
20. A year is about 365.25 days, so every four years we add a leap day.
21. The Moon is about 384,400 km away: you could line up about 30 Earths in the gap.
22. The Moon is drifting away from Earth by about an inch (2.5 cm) a year.
23. The Moon is the only place beyond Earth that people have visited. Apollo astronauts brought back 382 kg of Moon rock and soil.

Mars

24. Mars looks red because iron minerals in its dusty soil have rusted.
25. Mars has Olympus Mons, the largest volcano in the solar system. It is more than 40 km (25 miles) tall.
26. Mars has two small, potato-shaped moons called Phobos and Deimos.
27. Mars spins once every 24.6 hours, close to an Earth day, but a Mars year lasts 687 Earth days.

Jupiter and Saturn

28. Jupiter is the largest planet. It is 11 times wider than Earth, and about 1,000 Earths could fit inside it.
29. Jupiter’s Great Red Spot is a storm bigger than Earth that has lasted for hundreds of years.
30. NASA lists 115 officially recognised moons of Jupiter.
31. Jupiter’s moon Ganymede is the largest moon in the solar system. It is even bigger than the planet Mercury.
32. Galileo first saw Jupiter’s four biggest moons in 1610 with an early telescope.
33. Saturn is the only planet whose average density is lower than water’s.
34. Saturn had 274 confirmed moons in March 2025, more than any other planet.
35. Saturn’s moon Titan has lakes of liquid methane, and its moon Enceladus sprays jets of water into space.

Uranus, Neptune and Pluto

36. Uranus is tilted by almost 98 degrees, so it spins on its side and rolls around the Sun like a ball.
37. Uranus was the first planet found with a telescope, by William Herschel in 1781. It has 13 faint rings and 28 known moons.
38. Neptune was the first planet found by maths: astronomers predicted where it should be, and Johann Galle spotted it in 1846. It is the only planet you cannot see without a telescope.
39. Neptune is the windiest planet: its winds blow at more than 2,000 km/h, nine times stronger than Earth’s.
40. Pluto became a dwarf planet in 2006. NASA’s New Horizons flew past it in July 2015 and photographed its famous heart-shaped region. It has five known moons.

The solar system for kids: how big is it really?

Most posters squash the planets together and draw them far too large. They have to: if the Sun were the size of a 20 cm ball, Earth would be a 1.8 mm speck 21.5 metres away, and Neptune would be 649 metres away. That surprise is the best reason to build a scale model of the solar system yourself.

The Sun is about 109 times wider than Earth, and Jupiter about 11 times wider. Even at this small scale, the nearest star would be about 5,800 km from your Sun ball.

Make a scale model of the solar system in a park

This solar system model for kids uses one scale for both sizes and distances: 1 to 6.96 billion. The Sun is a 20 cm ball, so 1 mm in the model stands for 6,957 km in space. We worked out every number with a short Python script, using NASA’s diameters and average distances.

You need: a 20 cm ball, modelling clay or beads, a millimetre ruler, 9 labelled cards and a tape measure. Neptune needs about 650 metres of path, so use a long park path, a beach or a quiet track.

Stick each tiny planet to a labelled card. Earth’s Moon is a 0.5 mm speck 5.5 cm from Earth.

How to build a solar system model for kids, step by step

1. Roll the planets to size, measuring against the ruler, and fix each one to a labelled card.
2. Put the Sun ball at the start of your path.
3. Measure or pace out each distance from the Sun (all distances in the table start at the Sun). Big adult strides are roughly a metre each.
4. Leave a planet card at each stop. Look back at the Sun from Jupiter, and again from Neptune.
5. Talk about it. Walk it once and the solar system for kids stops being a flat poster.

Living in the US? Multiply metres by about 3.3 to get feet, or use our unit converter. Children can practise reading millimetres first with our measuring length worksheets.

Smaller space? The 1 AU = 1 m garden model

Short of space? A garden or school corridor still fits the solar system for kids: use 1 metre for each AU. Neptune is then 30.2 m from the Sun. Here the Sun is a 9 mm bead and the planets are too small to see, so use labelled cards.

How we calculated the scale model (a maths example)

Here is the maths behind our scale model. The scale factor is the model Sun divided by the real Sun: 200 mm ÷ 1,391,400 km. Multiply any real size or distance by it. For Earth, 12,756 km × 200 ÷ 1,391,400 = 1.83 mm. Earth’s distance, 149.6 million km, gives 21,500 mm, or 21.5 m. Checking the other rows is a good ratio lesson for Grades 6 to 8.

Teaching the solar system by age: what to focus on

Pitch the solar system for kids at the right level for each age group.

This topic works best as something they do, not just read. For younger children, play space bingo or the space hangman game to learn the names. Older children can draw the garden model on printable graph paper with 1 square for each AU; our guide to graph paper sizes explains which grid fits.

Common myths and mistakes to avoid

These myths turn up in almost every solar system for kids lesson.

• “Mercury is the hottest planet.” It is closest, but Venus is hotter because of its thick atmosphere.
• “Summer happens when Earth is closer to the Sun.” Seasons come from Earth’s 23.4° tilt.
• “The Sun is not a star.” It is a star, just much closer than the others.
• Quoting old moon counts. Check NASA’s current figure.

Worksheets and games for extra practice

Print the solar system worksheets for labelling, ordering and fact-matching, and then try the online planets quiz. For more topics, see our science worksheets.

Related guides and printables

• Science trivia for kids with answers
• Life cycles for kids
• How to improve concentration in kids
• Converting units worksheets for metres, centimetres and millimetres
• Isometric paper for drawing 3D rockets

Sources

Every fact in this guide was checked against these sources. Planet facts: NASA Science, Solar System Facts and the individual Sun, planet, Moon and Pluto fact pages (checked October 2026). Diameters, average distances and orbit lengths used in our scale model: NASA Planetary Fact Sheet (NSSDCA, updated March 2025). Definition of a planet: IAU 2006 General Assembly resolution votes.

Frequently asked questions

6 quick answers

What is the solar system for kids, in simple words?

It is the Sun and everything that travels around it: eight planets, five dwarf planets such as Pluto, hundreds of moons, and thousands of asteroids and comets.

What are the 8 planets for kids to learn, in order from the Sun?

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. A memory sentence such as “Many Very Excited Monkeys Jump Swiftly Under Nets” helps.

Why is Pluto not a planet anymore?

In 2006 the International Astronomical Union said a planet must clear the area around its orbit. Pluto shares its zone with many other icy objects, so it became a dwarf planet.

How do you make a scale model of the solar system for kids?

With a 20 cm ball as the Sun, Earth is a 1.8 mm bead 21.5 m away and Neptune is a 7 mm bead 649 m away. For a garden, use 1 m for each AU and labelled cards.

Which planet is the hottest, and which is the coldest?

Venus is the hottest, at about 467 °C. On NASA’s Planetary Fact Sheet, Neptune has the lowest average temperature of the eight planets, about −200 °C, just below Uranus at about −195 °C.

What age is best for teaching the solar system for kids?

Children aged 4 to 6 can learn about the Sun, the Moon and day and night. From about 6 they can learn the planets in order, and from 8 they can build a scale model.