Jupiter Trivia
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99 free Jupiter trivia questions with answers — science & nature quiz, new questions added Oct 2026.
This Jupiter trivia quiz is about the planet, the biggest thing in the Solar System after the Sun. It covers the numbers that make it a giant: 318 Earth masses, 11 Earth diameters, a ten-hour day that flattens it, a magnetic field that reaches nearly to Saturn, and a barycentre that lies outside the Sun. It then looks at the weather: the shrinking Great Red Spot, ammonia clouds, the polar cyclones Juno found and the Great Cold Spot, plus the metallic hydrogen and slow contraction that keep the planet radiating heat. The moons get their own section: Galileo's discovery and Marius's names, Ganymede bigger than Mercury, volcanic Io, ocean-bearing Europa, the Laplace resonance, Amalthea and the dusty rings. Then exploration and history: Pioneer 10, the Voyagers, the Galileo orbiter and its atmospheric probe, Juno's July 4 arrival, the crash of Comet Shoemaker–Levy 9, Rømer's speed of light, and finally the names, from Babylonian Marduk and the Chinese wood star to Guru, Phaethon, 'jovial' and the thunderbolt of the sky-father. Difficulty runs from easy to expert and is shown on each question, so it suits a classroom, a pub quiz or a space enthusiast. Every answer was checked against a reference page and each question carries its citation. Try our Planets and Solar System quizzes for more.
30 of 99 questions with answers and explanations. Play the quiz
Q 01Where does Jupiter rank in distance from the Sun?
Fifth
Fifth from the Sun, Jupiter is the first planet beyond the asteroid belt, and its gravity sculpts that belt, sweeping clear the empty lanes known as Kirkwood gaps.
Q 02Jupiter's mass is equal to roughly how many Earths?
About 300
About 300: Jupiter outweighs Earth 318 times and holds more than twice the mass of all the other planets combined, yet the Sun is about a thousand times heavier still.
Q 03Roughly how many Earths could fit inside Jupiter?
About 1,000
About 1,000 Earths would fit inside Jupiter, which is 11 times as wide, yet it weighs far less than a thousand Earths because it is made mostly of light gases rather than rock.
Q 04How long does Jupiter take to orbit the Sun?
About 11.9 years
Jupiter takes about 11.9 years to circle the Sun; ancient Chinese astronomers built their cycle of twelve earthly branches on that slow, nearly 12-year march across the sky.
Q 05Roughly how long is a day on Jupiter?
About 10 hours
A day on Jupiter lasts about 10 hours, the shortest of any planet; the spin is fast enough to bulge the planet, making it about 7% wider at the equator than from pole to pole.
Q 06Jupiter's atmosphere is made mostly of which two gases?
Hydrogen and helium
Hydrogen and helium are the same two gases that make up the Sun: Jupiter has the ingredients of a star but never grew massive enough to ignite.
Q 07What is the Great Red Spot?
A giant anticyclonic storm
The Great Red Spot is a giant anticyclonic storm: unlike a hurricane, it whirls around a centre of high pressure, and astronomers have watched it without a break since the 1870s.
Q 08Whose 'Permanent Spot' on Jupiter was long taken for the Great Red Spot?
Cassini
Cassini found his spot in 1665 and it was followed until 1713; the Great Red Spot enters the record only in 1831, and a 2024 study concluded the two were probably different spots.
Q 09In which part of Jupiter does the Great Red Spot sit?
The southern hemisphere
The southern hemisphere holds the spot at about 22 degrees south, penned between an eastward jet stream on its southern edge and a stronger westward one on its northern edge.
Q 10What has Jupiter's Great Red Spot been doing for more than a century?
Shrinking
Shrinking: in the late 1800s the spot was about three Earths wide, by 2004 it was half as long, and it has grown rounder as it narrows.
Q 11Jupiter's clouds are made mainly of crystals of what?
Ammonia
Jupiter's visible clouds are mostly ammonia crystals, with ammonium hydrosulfide below; the orange and brown streaks come from compounds welling up and changing colour in sunlight.
Q 12Why does Jupiter give off more heat than it receives from the Sun?
It is slowly contracting
It is slowly contracting: as Jupiter cools, its own gravity squeezes it and the squeeze heats its interior, a process called the Kelvin–Helmholtz mechanism.
Q 13Jupiter's magnetotail stretches out roughly as far as the orbit of which planet?
Saturn
Saturn's orbit is about where the tail ends: the solar wind stretches Jupiter's magnetic field into a tadpole-shaped tail more than a billion kilometres long.
Q 21Which moon of Jupiter is the most volcanically active body in the Solar System?
Io
Io, with over 400 active volcanoes, is the most volcanically active body in the Solar System; tidal flexing by Jupiter and the neighbouring Galilean moons heats its interior.
Q 22NASA launched a spacecraft in 2024 to study the hidden ocean of which moon of Jupiter?
Europa
Europa's ocean, sealed under an icy shell, may hold twice as much water as all of Earth's seas; Europa Clipper will fly past the moon 49 times to judge whether it could support life.
Q 23Jupiter's three inner large moons circle it in a locked 4:2:1 rhythm, which is an example of what?
An orbital resonance
Q 14What exotic material is thought to make up Jupiter's outer mantle and generate its magnetic field?
Fluid metallic hydrogen
Fluid metallic hydrogen, formed when pressure strips hydrogen's electrons so it conducts like a liquid metal, makes up much of Jupiter's interior and drives its dynamo.
Q 15Jupiter is the only planet whose shared centre of mass with the Sun lies where?
Outside the Sun's surface
Outside the Sun's surface, by about 7% of its radius: Jupiter is massive enough to make the Sun wobble around that point, the kind of wobble astronomers look for to find planets around other stars.
Q 16Where does Jupiter usually rank among the brightest natural objects in the night sky?
Third, after the Moon and Venus
Jupiter is usually the third-brightest natural object in the night sky, after the Moon and Venus; only at a favourable opposition can Mars briefly outshine it.
Q 17Which Galilean moon orbits farthest from Jupiter?
Callisto
Callisto is the outermost Galilean moon, orbiting about 1.88 million km from Jupiter, far enough to escape the tidal heating that shapes the inner three; its ancient surface is saturated with craters.
Q 18Which four moons were discovered by telescope in 1610?
Io, Europa, Ganymede and Callisto
Io, Europa, Ganymede and Callisto were the first moons seen circling another planet, and the sight of bodies orbiting something other than Earth dealt a blow to the old Earth-centred picture of the heavens.
Q 19Which German astronomer, who spotted them independently, gave Jupiter's four big moons the names that stuck?
Simon Marius
Simon Marius published the names in 1614, taking up Kepler's idea of calling them after lovers of Zeus; the name their discoverer chose, the Medicean Stars, never caught on.
Q 20Which moon of Jupiter is the largest moon in the Solar System, bigger than the planet Mercury?
Ganymede
Ganymede, wider than Mercury, is also the only moon known to make its own magnetic field, which gives it auroras of its own.
An orbital resonance: the innermost moon circles Jupiter four times and the next one twice for each orbit of the third, a pattern called a Laplace resonance, and the repeated tugs keep their interiors warm.
Q 24Which moon of Jupiter, found by Edward Barnard in 1892, was the last discovered by eye through a telescope?
Amalthea
Amalthea, spotted by Edward Emerson Barnard in 1892, was the last moon found by an astronomer looking through an eyepiece; every one since has turned up in photographs or digital images.
Q 25What are Jupiter's faint rings mostly made of?
Dust
Jupiter's rings are mostly fine dust, unlike Saturn's icy rings; the main ring is thought to be debris knocked off the small moons Adrastea and Metis by meteoroid impacts.
Q 26Which spacecraft discovered Jupiter's rings, in 1979?
Voyager
Voyager 1 discovered Jupiter's faint ring system in March 1979, photographing it in a long exposure as the probe looked back toward the Sun; Voyager 2 confirmed it that July.
Q 27Which was the first spacecraft to fly past Jupiter, in 1973?
Pioneer 10
Pioneer 10 flew past in December 1973 through radiation stronger than predicted, which triggered false commands and cost some pictures; its readings helped engineers harden the probes that followed.
Q 28How did NASA dispose of its first Jupiter orbiter in 2003, to avoid contaminating a moon?
Plunged it into Jupiter
Plunged it into Jupiter: after eight years in orbit, Galileo was deliberately burned up in the planet's atmosphere to protect one of its own discoveries, a possible ocean under a moon's icy crust.
Q 29For roughly how long did the 1995 atmospheric entry probe transmit from inside Jupiter's atmosphere?
About an hour
About an hour: the probe parachuted into the clouds in December 1995 and sent data for 58 minutes before the rising heat and pressure silenced it.
Q 30NASA's Juno spacecraft arrived at Jupiter on which US holiday in 2016?
July 4
July 4, Independence Day, was still the date in the United States when Juno arrived in 2016: after a five-year flight it fired its main engine for 35 minutes to let Jupiter's gravity capture it.