Solar System Planets Flashcards: Key Facts
36 cards · free to study, print and copy
Solar System Planets Flashcards: Key Facts
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About this deck
This deck asks short questions about the solar system and gives a concise answer on the back. It covers the order of the planets, their sizes and notable features, a few famous moons, dwarf planets and the main regions such as the asteroid belt and Kuiper Belt.
It is written for elementary and middle school science, and works as a refresher for adults. Figures are rounded to the level usually taught in school.
Numbers like moon counts change as astronomers confirm new discoveries, so the deck focuses on facts that stay stable.
Study tips
- Learn the planet order first with a sentence like "My Very Educated Mother Just Served Us Nachos."
- Group the planets: four rocky inner planets, two gas giants, two ice giants.
- Link each planet to one vivid feature: Mars is red, Jupiter has the Great Red Spot, Uranus spins on its side.
- Draw the solar system from memory after studying and check the order against the deck.
All 36 cards
| Front | Back |
|---|---|
| Order of the planets from the Sun | Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune |
| How many planets are in the solar system? | 8 |
| What kind of star is the Sun? | A yellow dwarf (G-type main-sequence star) |
| Closest planet to the Sun | Mercury |
| Smallest planet | Mercury |
| Hottest planet | Venus, because its thick CO₂ atmosphere traps heat |
| Planet that spins backward compared with most others | Venus (Uranus is also tilted onto its side) |
| Only planet known to support life | Earth |
| Earth's natural satellite | The Moon |
| Why Mars looks red | Iron oxide (rust) in its surface dust and rocks |
| Tallest volcano in the solar system | Olympus Mons, on Mars |
| Mars's two moons | Phobos and Deimos |
| Largest planet | Jupiter |
| Jupiter's Great Red Spot | A giant storm larger than Earth |
| Jupiter's four large Galilean moons | Io, Europa, Ganymede, Callisto |
| Largest moon in the solar system | Ganymede (Jupiter) |
| Planet best known for its bright rings | Saturn (Jupiter, Uranus and Neptune have fainter rings) |
| Saturn's largest moon, with a thick atmosphere | Titan |
| Planet that rotates on its side | Uranus, tilted about 98° |
| Farthest planet from the Sun | Neptune |
| Planet with the fastest winds | Neptune |
| Inner (terrestrial) planets | Mercury, Venus, Earth, Mars: small, rocky |
| Gas giants | Jupiter and Saturn: mostly hydrogen and helium |
| Ice giants | Uranus and Neptune: water, ammonia and methane ices under H/He atmospheres |
| Asteroid belt | Region of rocky bodies between Mars and Jupiter |
| Largest object in the asteroid belt | Ceres, a dwarf planet |
| Kuiper Belt | Icy region beyond Neptune; home to Pluto and many small bodies |
| Five officially recognized dwarf planets | Ceres, Pluto, Haumea, Makemake, Eris |
| Year Pluto was reclassified as a dwarf planet | 2006 |
| Astronomical unit (AU) | Average Earth–Sun distance, about 150 million km (93 million miles) |
| How long sunlight takes to reach Earth | About 8 minutes 20 seconds |
| Comet | Icy body that grows a glowing coma and tail near the Sun |
| Meteor vs. meteorite | A meteor is the streak of light in the sky; a meteorite is a piece that reaches the ground |
| Length of one Earth year | About 365.25 days |
| Planet with the longest day (one rotation) | Venus, about 243 Earth days |
| Planet with the shortest day | Jupiter, about 10 hours |
Frequently asked questions
›Why is Pluto not a planet anymore?
In 2006 the International Astronomical Union defined a planet as a body that has cleared its orbit of other objects. Pluto has not, so it was reclassified as a dwarf planet.
›Which planet has the most moons?
Saturn has the most confirmed moons as of recent counts, ahead of Jupiter. The totals keep changing as new small moons are confirmed.
›Why is Venus hotter than Mercury?
Venus has a thick carbon dioxide atmosphere that traps heat. Mercury has almost no atmosphere, so heat escapes.
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