Jupiter Trivia
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50 free Jupiter trivia questions with answers — science & nature quiz, new questions added Aug 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 50 questions with answers and explanations. Play the quiz
Q 01Where does Jupiter rank in distance from the Sun?
Fifth
Jupiter is the fifth planet from the Sun, the first of the giant planets beyond the asteroid belt, after Mercury, Venus, Earth and Mars.
Q 02Jupiter's mass is roughly how many times that of Earth?
318
Jupiter's mass is about 318 times Earth's, nearly 2.5 times that of all the other planets combined, yet under a thousandth of the Sun's.
Q 03Jupiter's diameter is about how many times Earth's?
11
Jupiter's equatorial diameter of about 143,000 km is roughly 11 times Earth's 12,742 km and about a tenth of the Sun's.
Q 04How long does Jupiter take to orbit the Sun?
About 11.9 years
Jupiter takes about 11.9 years to orbit the Sun; Chinese astronomers called it the Year Star and tied the twelve earthly branches to its near-12-year cycle.
Q 05Roughly how long is a day on Jupiter?
About 10 hours
A Jovian day lasts about 10 hours (9 h 56 m), the fastest spin of any planet; the rotation flattens Jupiter into an oblate spheroid about 7% wider at the equator.
Q 06Jupiter's atmosphere is made mostly of which two gases?
Hydrogen and helium
About 76% hydrogen and 24% helium by mass, close to the primordial mix of the solar nebula.
Q 07What is the Great Red Spot?
A giant anticyclonic storm
The Great Red Spot is a giant anticyclonic storm, spinning counterclockwise about once every six Earth days and rising some 8 km above the surrounding cloud tops.
Q 08Since when has the Great Red Spot been continuously observed?
1831
The Great Red Spot has been observed continuously since 1831; earlier sightings by Robert Hooke (1664) and Cassini (1665) are disputed and may have been a different storm.
Q 09In which part of Jupiter does the Great Red Spot sit?
The southern hemisphere
The Great Red Spot sits in Jupiter's southern hemisphere at about 22 degrees south latitude, pinned between the South Equatorial Belt and the South Tropical Zone.
Q 10Roughly how wide was the Great Red Spot in the late 1800s, before it began shrinking?
About 41,000 km
In the late 1800s the Great Red Spot spanned about 41,000 km, over three Earth diameters; by 2015 it had shrunk to roughly 16,500 by 10,940 km.
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 12Which mechanism makes Jupiter radiate more heat than it receives from the Sun?
Kelvin–Helmholtz contraction
Kelvin–Helmholtz contraction drives it: Jupiter slowly contracts under its own gravity, converting gravitational energy into heat, so its interior heat outstrips what it absorbs from the Sun.
Q 13Jupiter's magnetotail stretches out roughly as far as the orbit of which planet?
Saturn
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 22Which icy moon of Jupiter is a prime target in the search for life because of its subsurface ocean?
Europa
Europa hides a salty ocean beneath its icy shell, with Hubble detecting possible water-vapour plumes in the 2010s; NASA launched the Europa Clipper mission in October 2024 to study it.
Q 23The three inner Galilean moons orbit in a 4:2:1 pattern known as what?
A Laplace resonance
The 4:2:1 pattern is a Laplace resonance: each moon receives a gravitational tug at the same point every orbit, keeping their orbits slightly elliptical and their interiors tidally warmed.
Jupiter's magnetotail, the downwind side of the strongest planetary magnetosphere in the Solar System, stretches almost to the orbit of Saturn, hundreds of millions of kilometres away.
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 barycentre with the Sun lies where?
Outside the Sun's surface
Jupiter's barycentre with the Sun lies outside the Sun's surface, about 7% of a solar radius above it, because Jupiter holds over twice the mass of all the other planets combined.
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 first seen in January 1610 through an early telescope, the first moons known to orbit a planet other than Earth; they are the Galilean moons.
Q 19Who gave the four big moons the names that stuck, taken from Zeus's lovers?
Simon Marius
Simon Marius published the names that stuck, drawn from Zeus's lovers, in his 1614 Mundus Iovialis; their discoverer had called them the Medicean Stars after his patrons.
Q 20Which moon of Jupiter is the largest moon in the Solar System, bigger than the planet Mercury?
Ganymede
Ganymede, 5,268 km across, is the largest moon in the Solar System, outsizing Mercury, and the only moon known to generate its own magnetic field.
Q 24Which moon, found by Barnard in 1892, was the last discovered by eye through a telescope?
Amalthea
Amalthea, spotted by E. E. Barnard at Lick Observatory in 1892, was the last moon in the Solar System discovered by direct visual observation; everything since has come from photographs or spacecraft.
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 made the first flyby of Jupiter on 3 December 1973, having already been the first probe to cross the asteroid belt; its signal was last detected in 2003.
Q 28Which was the first spacecraft to orbit Jupiter, arriving in December 1995?
Galileo
Galileo entered orbit on 7 December 1995 and circled Jupiter for nearly eight years, dropping a probe into the atmosphere despite its jammed high-gain antenna; it was deorbited in September 2003.
Q 29For roughly how long did the 1995 atmospheric entry probe transmit from inside Jupiter's atmosphere?
About an hour
The 1995 entry probe parachuted into Jupiter's atmosphere on 7 December and transmitted for about an hour (58 minutes), descending some 150 km before pressure and heat destroyed it.
Q 30NASA's Juno spacecraft arrived at Jupiter on which US holiday in 2016?
July 4
Juno entered orbit on 4 July 2016, Independence Day, after a five-year journey; it returned the first close-up images of Jupiter's poles and found clusters of polar cyclones.