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The solar system flash cards

Flash cards on the solar system: the Sun, the eight planets in order with a key fact each, dwarf planets, moons, asteroids, comets, gravity, seasons and Moon phases.

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The cards, front and back

1
Front
What is the solar system?
Back
The Sun and everything held in orbit around it by gravity, including the eight planets, their moons, dwarf planets, asteroids and comets.
2
Front
List the eight planets in order from the Sun.
Back
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
3
Front
What is the Sun?
Back
A star: a huge ball of hot gas, mostly hydrogen and helium, that releases energy by nuclear fusion in its core. It holds almost all of the solar system's mass.
4
Front
Mercury
Back
The smallest planet and the closest to the Sun. It has almost no atmosphere and no moons, so its temperature swings hugely between day and night.
5
Front
Venus
Back
The hottest planet, because its thick carbon dioxide atmosphere traps heat. It spins in the opposite direction to most planets, and very slowly.
6
Front
Earth
Back
The third planet from the Sun and the only place known to support life. It has liquid water on its surface and one natural satellite, the Moon.
7
Front
Mars
Back
A rocky planet that looks red because of iron oxide (rust) in its dust. It has two small moons, Phobos and Deimos, and the tallest known volcano in the solar system, Olympus Mons.
8
Front
Jupiter
Back
The largest planet, a gas giant. Its Great Red Spot is a giant storm that has been observed for well over a century.
9
Front
Saturn
Back
A gas giant famous for its bright rings, which are made of ice and rock. It is less dense than water.
10
Front
Uranus
Back
An ice giant that is tilted so far over that it spins on its side. Methane in its atmosphere makes it look blue-green.
11
Front
Neptune
Back
The farthest planet from the Sun, an ice giant with the strongest winds measured in the solar system.
12
Front
Which planets are rocky and which are giants?
Back
The inner four (Mercury, Venus, Earth, Mars) are small and rocky. The outer four are giants: Jupiter and Saturn are gas giants, and Uranus and Neptune are ice giants.
13
Front
What is a dwarf planet?
Back
A body that orbits the Sun and is round, but has not cleared other objects from its orbit. Pluto was reclassified as a dwarf planet in 2006. Ceres and Eris are others.
14
Front
Where is the asteroid belt?
Back
Between the orbits of Mars and Jupiter. It contains many rocky objects of different sizes.
15
Front
What is the Kuiper belt?
Back
A region of icy objects beyond the orbit of Neptune. Pluto is one of its largest members.
16
Front
What is a comet?
Back
A small body of ice and dust. When its orbit brings it near the Sun, the ice turns to gas and it forms a glowing head and a tail that points away from the Sun.
17
Front
What keeps the planets in orbit?
Back
The gravitational pull of the Sun. Without it, each planet would carry on in a straight line.
18
Front
What causes day and night?
Back
Earth spinning on its axis, about once every 24 hours. The side facing the Sun has day.
19
Front
What causes the seasons?
Back
The tilt of Earth's axis, about 23.5°. As Earth orbits the Sun, each hemisphere leans towards the Sun for part of the year (summer) and away for the other part (winter). It is not caused by changes in distance from the Sun.
20
Front
How long does Earth take to orbit the Sun?
Back
About 365¼ days, which is why a leap year adds an extra day every four years.
21
Front
Why does the Moon have phases?
Back
The Moon is always half lit by the Sun. As it orbits Earth, about once a month, we see different amounts of that lit half.
22
Front
How long does light from the Sun take to reach Earth?
Back
About 8 minutes.

How to use this template

This deck takes you on a tour of the solar system: what it contains, the Sun, all eight planets in order with a memorable fact about each, rocky planets and giants, dwarf planets including Pluto, the asteroid belt, the Kuiper belt and comets, then the Earth and Moon basics that come up in every science course: gravity and orbits, day and night, the seasons, the length of a year and the phases of the Moon. It suits primary and middle school science, Year 5 to Year 9, GCSE and IGCSE physics space topics, high school earth and space science and anyone who loves astronomy. Learn it in Learn mode, test yourself with Test mode, and let spaced repetition do the rest. Print it double-sided for a classroom space quiz.

Tips

Make up your own memory sentence for the order of the planets, with words starting M, V, E, M, J, S, U, N.
Learn one stand-out fact for each planet first, then add a second fact once those are secure.
Explain the seasons to someone else using a ball and a lamp. If you can explain the tilt, you have understood it.
Be careful with numbers of moons for the giant planets: new moons are still being found, so courses often avoid asking for exact counts.
Sort the planets into rocky planets, gas giants and ice giants on paper, then check against the cards.

Make it fit

Add cards on stars, galaxies, the life cycle of a star or the Big Bang if your course includes them.
Add a card for each space mission your class studies.
Make reverse cards with the fact on the front and the planet's name on the back.
For younger learners, keep only the planet cards and the day, night and seasons cards.

Updated October 28, 2026

The cards, front and back

How to use this template

Tips

Make it fit

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