I’ve always been fascinated by the night sky. When I was a kid, my dad and I would lie on our backyard deck with a telescope, picking out planets and stars. Those memories sparked a lifelong curiosity about our celestial neighbors.
Whether you’re planning a space-themed party, looking for educational activities for kids, or just wanting to test your cosmic knowledge, I’ve put together over 100 planet trivia questions that are out of this world!
From basic solar system facts to mind-blowing cosmic phenomena, these questions will challenge beginners and astronomy buffs alike. I’ve tested these out during family game nights and even used them for my nephew’s science class presentation—they were a huge hit!
Solar System Basics
Let’s start with some fundamental questions about our cosmic neighborhood. I find these are great warm-up questions that anyone can take a shot at answering, regardless of their astronomy knowledge.
- How many planets are in our solar system?
Answer: 8 (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune) - Which planet is closest to the sun?
Answer: Mercury - What is the largest planet in our solar system?
Answer: Jupiter - What keeps planets in orbit around the sun?
Answer: Gravity - What are the four inner planets of our solar system also called?
Answer: Terrestrial planets - What are the four outer planets of our solar system also called?
Answer: Gas giants (though technically Uranus and Neptune are ice giants) - Which planet has the most moons?
Answer: Saturn (currently 83 confirmed moons) - What is the hottest planet in our solar system?
Answer: Venus - What is the main component of the sun?
Answer: Hydrogen - What is the center of our solar system?
Answer: The Sun - What force pulls objects toward the center of the Earth?
Answer: Gravity - What’s the name of the cloud of icy objects beyond Neptune?
Answer: Kuiper Belt - What is the asteroid belt?
Answer: A region between Mars and Jupiter filled with asteroids - In what galaxy is our solar system located?
Answer: Milky Way Galaxy - Approximately how old is our solar system?
Answer: About 4.6 billion years - What is the name of the theory that explains the formation of our solar system?
Answer: Nebular Hypothesis - What term describes the path a planet takes around the sun?
Answer: Orbit - What makes up Saturn’s rings?
Answer: Ice, rock, and dust particles - What is the Great Red Spot?
Answer: A giant storm on Jupiter - What is a light-year?
Answer: The distance light travels in one year (about 5.88 trillion miles)
If you’re looking for more brain-testing questions beyond our solar system, you might enjoy our math trivia questions that explore another type of universal language!
Earth and Moon Trivia
Our home planet and its faithful companion have some fascinating features. My daughter’s science project last year focused on moon phases, and these questions helped her understand our closest celestial neighbor better.
- What percentage of Earth is covered by water?
Answer: About 71% - What is the only natural satellite of Earth?
Answer: The Moon - How long does it take for the Moon to orbit Earth?
Answer: 27.3 days - What causes the tides on Earth?
Answer: The gravitational pull of the Moon (and to a lesser extent, the Sun) - What is the name of Earth’s protective magnetic field?
Answer: Magnetosphere - Which layer of Earth’s atmosphere contains the ozone layer?
Answer: Stratosphere - What is the highest mountain on Earth?
Answer: Mount Everest - What is the deepest point in Earth’s oceans?
Answer: Challenger Deep in the Mariana Trench - How many layers does Earth have?
Answer: Four main layers (inner core, outer core, mantle, and crust) - What phenomenon causes the seasons on Earth?
Answer: Earth’s axial tilt as it orbits the Sun - What is the approximate circumference of Earth at the equator?
Answer: 24,901 miles (40,075 km) - What are the dark areas visible on the Moon called?
Answer: Maria (singular: mare) or “seas” - Who was the first person to walk on the Moon?
Answer: Neil Armstrong - How old is the Moon estimated to be?
Answer: About 4.5 billion years - What is the temperature range on the Moon’s surface?
Answer: From about -280°F (-173°C) at night to 260°F (127°C) during the day - What causes lunar eclipses?
Answer: Earth passing between the Sun and Moon, casting a shadow on the Moon - What is the approximate distance between Earth and the Moon?
Answer: About 238,855 miles (384,400 km) on average - What is regolith?
Answer: The layer of loose, fragmented material covering solid rock on the Moon’s surface - How much does the Moon’s gravity compare to Earth’s?
Answer: About 1/6 of Earth’s gravity - What is the name of the phenomenon where the Moon appears larger when near the horizon?
Answer: Moon illusion
Looking for more ways to spark interesting discussions? Check out our deep topics to talk about that include fascinating philosophical questions about space and existence.
Inner Planets
The four planets closest to the sun each have their own unique characteristics. I remember making a solar system model with my son for his science fair—getting the sizes and distances right was tricky, but we learned so much about these fascinating worlds!
- Why is Mercury difficult to observe from Earth?
Answer: Because it’s so close to the Sun - What planet is often called Earth’s “sister planet” due to similar size?
Answer: Venus - What gives Mars its distinctive reddish appearance?
Answer: Iron oxide (rust) on its surface - Which inner planet has the longest day?
Answer: Venus (a Venusian day is longer than its year) - What is the largest volcano in the solar system?
Answer: Olympus Mons on Mars - Which inner planet has no moons?
Answer: Mercury and Venus - What is the atmospheric pressure on Venus compared to Earth?
Answer: About 90 times greater - What are the two moons of Mars called?
Answer: Phobos and Deimos - What is the surface temperature of Mercury during the day?
Answer: About 800°F (430°C) - What unique feature of Venus’s rotation makes it different from most planets?
Answer: It rotates in the opposite direction (retrograde rotation) - What is the length of a year on Mercury?
Answer: 88 Earth days - What is the main component of Mars’ polar ice caps?
Answer: Water ice and carbon dioxide ice - What famous canyon system on Mars is much larger than Earth’s Grand Canyon?
Answer: Valles Marineris - Which planet has the most similar day length to Earth?
Answer: Mars (24 hours and 37 minutes) - What causes Venus to be so hot despite not being the closest planet to the Sun?
Answer: Runaway greenhouse effect - What is the approximate diameter of Mercury?
Answer: 3,031 miles (4,880 km) - What is a “dust devil” on Mars?
Answer: A whirlwind or tornado-like phenomenon - What color does the sky appear on Mars?
Answer: Pinkish-red during the day, bluish near sunset - What are the “canali” that Italian astronomer Giovanni Schiaparelli observed on Mars?
Answer: What he thought were channels or canals (later proved to be an optical illusion) - Which inner planet has the most eccentric (least circular) orbit?
Answer: Mercury
If you’re looking for more interesting conversation starters for your next gathering, check out our collection of interesting topics to talk about that include space exploration and scientific discoveries.
Outer Planets
The gas and ice giants of our solar system are truly spectacular. I was lucky enough to see Saturn through a professional telescope at an observatory once, and those rings literally took my breath away! These massive worlds hold some of our solar system’s most fascinating secrets.
- How many rings does Saturn have?
Answer: 7 main rings, with thousands of smaller ringlets - What creates the blue color of Neptune?
Answer: Methane in its atmosphere - Which planet has the Great Dark Spot?
Answer: Neptune - What is the main component of Jupiter and Saturn?
Answer: Hydrogen and helium - Which outer planet is known for being tipped on its side?
Answer: Uranus (it rotates at a 98-degree angle to its orbit) - What is the largest moon in the solar system?
Answer: Ganymede (a moon of Jupiter) - Which planet has a moon with methane lakes on its surface?
Answer: Saturn (its moon Titan) - What spacecraft provided most of our detailed images of the outer planets?
Answer: Voyager 1 and Voyager 2 - Which planet has the strongest winds in the solar system?
Answer: Neptune (up to 1,200 mph or 2,000 km/h) - How long is a day on Jupiter?
Answer: About 10 hours - What is the hexagonal cloud pattern at Saturn’s north pole called?
Answer: Saturn’s hexagon - Which planet’s interior might contain a “diamond rain”?
Answer: Neptune and Uranus - What is the approximate temperature at Jupiter’s cloud tops?
Answer: About -230°F (-145°C) - Which of Jupiter’s moons is known for its extreme volcanic activity?
Answer: Io - Which outer planet has only been visited by one spacecraft?
Answer: Uranus (by Voyager 2) - Which planet’s atmosphere contains helium rain?
Answer: Saturn - What is the approximate diameter of Jupiter?
Answer: 86,881 miles (139,820 km) - Which moon of Saturn has geysers of water erupting from its south pole?
Answer: Enceladus - What causes the auroras on Jupiter?
Answer: Interaction between Jupiter’s magnetic field and charged particles from the Sun and its moon Io - What are the dark, narrow rings around Uranus called?
Answer: The Epsilon Ring system
In need of more celestial conversation starters? Our collection of space trivia questions and answers goes beyond planets to explore the wider universe.
Dwarf Planets and Beyond
My fascination with Pluto started when it was still classified as the ninth planet! Its 2006 reclassification sparked some heated debates in our household. The dwarf planets and other objects in our solar system might be small, but they’re packed with intriguing features.
- What is a dwarf planet?
Answer: A celestial body that orbits the Sun, has enough mass to be round, but has not cleared its orbit of other objects - How many recognized dwarf planets are in our solar system?
Answer: Five officially recognized (Pluto, Eris, Haumea, Makemake, and Ceres) - When was Pluto reclassified from a planet to a dwarf planet?
Answer: 2006 - Which dwarf planet is located in the asteroid belt?
Answer: Ceres - What is the largest dwarf planet?
Answer: Either Pluto or Eris (they’re very close in size) - What is the heart-shaped region on Pluto called?
Answer: Tombaugh Regio - Which NASA spacecraft provided the first close-up images of Pluto?
Answer: New Horizons - What is Pluto’s largest moon?
Answer: Charon - What is the hypothetical ninth planet that might exist far beyond Neptune?
Answer: Planet Nine - What is the Oort Cloud?
Answer: A spherical shell of icy objects at the edge of our solar system - What dwarf planet was named after the goddess of discord?
Answer: Eris - Approximately how long does it take Pluto to orbit the Sun?
Answer: 248 Earth years - What is unique about the dwarf planet Haumea’s shape?
Answer: It’s elongated or ellipsoidal rather than spherical - What is the surface temperature on Pluto?
Answer: About -375°F (-225°C) - What is the brightest dwarf planet as seen from Earth?
Answer: Ceres
Need more brain teasers? Try our collection of common sense trivia questions that challenge your everyday knowledge.
Space Exploration Trivia
Our journey to understand planets has led to some incredible missions. I remember staying up late to watch the Mars Curiosity rover landing—what an exciting moment for space exploration! These questions highlight our efforts to study our celestial neighbors.
- What was the first spacecraft to visit Mercury?
Answer: Mariner 10 - Which rovers have successfully operated on Mars?
Answer: Sojourner, Spirit, Opportunity, Curiosity, and Perseverance - What NASA mission orbited Saturn from 2004 to 2017?
Answer: Cassini-Huygens - Which spacecraft is currently studying the Sun up close?
Answer: Parker Solar Probe - What spacecraft made the first flyby of Pluto?
Answer: New Horizons - Which country successfully landed the first spacecraft on the far side of the Moon?
Answer: China (Chang’e 4) - What is the name of NASA’s mission to return samples from Mars?
Answer: Mars Sample Return - Which spacecraft discovered the underground ocean on Jupiter’s moon Europa?
Answer: Galileo - What is the name of NASA’s next-generation space telescope launched in 2021?
Answer: James Webb Space Telescope - Which spacecraft entered orbit around Mercury in 2011?
Answer: MESSENGER - What is the name of the helicopter that flew on Mars?
Answer: Ingenuity - Which space agency operates the Venus Express mission?
Answer: European Space Agency (ESA) - What spacecraft detected water plumes on Saturn’s moon Enceladus?
Answer: Cassini - What was the first spacecraft to visit all four gas giant planets?
Answer: Voyager 2 - Which mission discovered evidence of ancient flowing water on Mars?
Answer: Mars Reconnaissance Orbiter
If space exploration fascinates you, you might also enjoy testing your knowledge about other scientific discoveries with our science riddles collection.
Extreme Planet Facts
During a planetarium visit last year, I learned some facts about our solar system that absolutely blew my mind. These questions highlight the most extreme and unusual aspects of planetary science that never fail to amaze me.
- What planet has the most extreme temperature variations in the solar system?
Answer: Mercury - Which planet has the longest day in our solar system?
Answer: Venus (243 Earth days) - What planet has a day shorter than its year?
Answer: Mercury - Which planet has the most powerful magnetic field?
Answer: Jupiter - What planet has the tallest mountain in the solar system?
Answer: Mars (Olympus Mons) - Which planet has the most violent storms in the solar system?
Answer: Jupiter or Neptune (debated) - What planet has the lowest density in the solar system?
Answer: Saturn (it would float in water if there were a bath big enough) - Which planet has the most eccentric (oval-shaped) orbit?
Answer: Mercury - What planet rotates in the opposite direction to most other planets?
Answer: Venus - Which planet has the most extreme seasons?
Answer: Uranus (due to its extreme axial tilt)
For more mind-bending questions that make you think outside the box, check out our collection of hypothetical questions that spark fascinating discussions.
Why Planet Trivia is Perfect for Everyone
I don’t know about you, but I think planet trivia strikes that perfect balance between entertainment and education. Last summer, I organized a stargazing night for my friends where we quizzed each other on space facts while watching for shooting stars. What made it special wasn’t just learning new things—it was sharing that sense of wonder about our universe.
Planet trivia works brilliantly for family gatherings, classroom activities, or even road trips (we played “name that planet” for hours during our cross-country drive last year!). It sparks curiosity in kids and often leads to fascinating conversations that go way beyond the initial questions.
If you’re looking for more ways to start meaningful conversations, check out our collection of philosophical questions that pair perfectly with stargazing sessions.
Final Thoughts
Phew! We’ve journeyed through the entire solar system with these trivia questions! I hope you’ve learned some fascinating new facts about our cosmic neighborhood. My family has had hours of fun testing each other with these questions, and they’ve sparked some amazing conversations about space, science, and our place in the universe.
Did you know all the answers? Or did some of these planet facts surprise you? I’d love to know which question you found most interesting! For me, it’s always been the fact that Saturn would float in water—something about that giant planet bobbing like a rubber duck just tickles my imagination.
If you’re looking for more ways to engage your mind and spark interesting conversations, don’t miss our collection of would you rather questions that can be just as thought-provoking as contemplating the cosmos.
Keep looking up at the stars and wondering—that’s where all great science begins!