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50 free Kuiper Belt trivia questions with answers — science & nature quiz, new questions added Aug 2026.
This Kuiper Belt trivia quiz covers the ring of icy bodies beyond Neptune, twenty times wider than the asteroid belt and home to Pluto and most of the Solar System's dwarf planets. The easy questions handle the basics: where the belt starts and ends, what its objects are made of, which Dutch astronomer it is named after, the spacecraft that flew through it, and why Pluto was demoted in 2006. From there it moves through the discovery story, from Kenneth Edgeworth's 1943 paper and Julio Fernández's comet belt to the five-year search by David Jewitt and Jane Luu that turned up 1992 QB1. The harder half is for astronomy fans: plutinos and twotinos, cubewanos and the cold classical belt, the Kuiper cliff nobody can explain, Neptune's migration and the Nice model, Triton's retrograde capture, Haumea's rings and collisional family, Quaoar's impossible rings, Sedna's 11,400-year orbit, the snowman shape of Arrokoth and the mysterious clustering that hints at Planet Nine. If you enjoyed our Pluto or Solar System quizzes, this is the deep dive on the region beyond the planets. Every answer was checked against the encyclopaedia entries for the Kuiper belt, its major objects, New Horizons and the astronomers named before publishing.
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Q 01The Kuiper Belt extends from Neptune's orbit at 30 AU out to roughly how far from the Sun?
About 50 AU
Its inner edge is Neptune's orbit, and the whole thing is about twenty times as wide as the asteroid belt.
Q 02Compared with the asteroid belt, roughly how much wider is the Kuiper Belt?
20 times
It is also somewhere between 20 and 200 times as massive.
Q 03Unlike rocky asteroids, most Kuiper Belt objects are composed largely of what?
Frozen ices like methane and water
At the belt's temperature of only about 50 K, compounds that would be gases nearer the Sun stay frozen solid.
Q 04The belt is named after which Dutch astronomer, who speculated about such a disc in 1951?
Gerard Kuiper
He is often called the father of modern planetary science, and had eyesight sharp enough to see magnitude 7.5 stars unaided.
Q 05Which Irish army officer and amateur astronomer proposed a disc of bodies beyond Neptune in the 1930s and 1940s, giving the belt its alternative name?
Kenneth Edgeworth
He argued the outer solar nebula was too thinly spread to form planets, so it condensed into 'a very large number of comparatively small bodies'.
Q 06According to David Jewitt, which Uruguayan astronomer 'most nearly deserves the credit' for predicting the belt with his 1980 comet-belt paper?
Julio Fernández
He calculated that for every short-period comet the Oort cloud sent inward, 600 would have to be flung into interstellar space.
Q 07Ironically, Kuiper's own 1951 idea assumed what about Pluto that would have meant no belt exists today?
It was massive enough to scatter them all away
Astronomers then thought Pluto was roughly Earth-mass; Charon's discovery in 1978 showed it was only 0.2% of that.
Q 08Which two astronomers announced the first modern Kuiper Belt object, 1992 QB1, after a five-year search?
David Jewitt and Jane Luu
Jewitt had told his graduate student, 'If we don't, nobody will'; the pair later shared the 2012 Kavli Prize.
Q 09What name did 1992 QB1 finally receive in 2018?
Albion
Its discoverers wanted 'Smiley', but that was taken by an asteroid, so it was named for the primeval man of William Blake's mythology.
Q 10Classical Kuiper Belt objects are nicknamed 'cubewanos' after what?
The QB1 in 1992 QB1's designation
IAU rules say classical objects must be named for mythological beings associated with creation.
Q 11Jane Luu, co-discoverer of the first Kuiper Belt object, came to the United States in 1975 as a refugee from which country?
Vietnam
She graduated as her high school's valedictorian and studied physics at Stanford before joining Jewitt at MIT.
Q 12Which device, used to spot moving objects between paired photographs, did both Pluto's discoverer and the Kuiper Belt searchers rely on?
A blink comparator
Examining one pair of plates took Jewitt and Luu about eight hours until CCDs let them blink images on a computer screen.
Q 13Roughly how many Kuiper Belt objects at least 100 km across are thought to exist?
Over 100,000
Q 21A 2014 estimate put the total mass of the Kuiper Belt at roughly how many Earth masses?
About 0.02
That small mass puzzles modellers, because building objects over 100 km across by collisions needs far more material.
Q 22Which popular account of giant-planet migration, named after a French city, reproduces much of the belt's structure?
The Nice model
In it, a Jupiter-Saturn 1:2 resonance flings Uranus and Neptune outward through the primordial disc, ejecting 99% of the belt's original population.
Q 23Which large moon of Neptune is thought to be a captured Kuiper Belt object, the only big moon with a retrograde orbit?
Triton
Over a thousand were actually found in the twenty years after 1992 QB1.
Q 14Which region, not the Kuiper Belt proper, is now thought to be the true source of short-period comets?
The scattered disc
Neptune's outward migration 4.5 billion years ago left it as a dynamically active zone whose objects it can still disturb.
Q 15How much more distant than the Kuiper Belt is the hypothesised Oort cloud thought to be?
About a thousand times
Unlike the belt, the Oort cloud is believed to be mostly spherical and is the source of long-period comets.
Q 16Kuiper Belt objects that share Pluto's 2:3 orbital resonance with Neptune are known as what?
Plutinos
About 200 are known; IAU rules say all of them must be named for underworld deities.
Q 17What is the nickname for objects in the sparsely populated 1:2 resonance with Neptune at about 47.7 AU?
Twotinos
They complete half an orbit for every one of Neptune's.
Q 18What is the 'Kuiper cliff'?
A sharp falloff in objects beyond about 48 AU
Models predicted large objects should double beyond 50 AU; the falloff is real, unexplained, and one suggested cause is an unseen planet.
Q 19Overall, the Kuiper Belt is described as more resembling what shape than a belt?
A torus or doughnut
Its main concentration extends up to ten degrees outside the ecliptic plane, with a more diffuse spread further out.
Q 20The 'dynamically cold' and 'dynamically hot' populations of the classical belt are named by analogy to what?
Particles in a gas
The cold group has near-circular, low-inclination orbits, is redder and brighter, and has more binaries; the hot group is inclined by up to 30 degrees.
It is only 14% larger than Pluto and its surface is made of similar ices; it may have been captured while part of a binary.
Q 24Which of Saturn's moons, like Neptune's largest moon, may have originated in the Kuiper Belt?
Phoebe
Both are listed as possible immigrants from the region in the belt's encyclopaedia entry.
Q 25Pluto was discovered in 1930 by which astronomer, making it the first known Kuiper Belt object?
Clyde Tombaugh
He was 23 when the Lowell Observatory director gave him the job of hunting Planet X.
Q 26In what year did the International Astronomical Union redefine 'planet' and reclassify Pluto as a dwarf planet?
2006
The new rule that a planet must have 'cleared the neighbourhood around its orbit' was the sticking point, since Pluto shares its orbit with many sizeable bodies.
Q 27How many known moons does Pluto have?
Five
Charon is over half Pluto's diameter, so the pair's centre of mass lies outside either body and they are sometimes called a binary.
Q 28How long does sunlight take to reach Pluto at its average distance of 39.5 AU?
About 5.5 hours
Its eccentric orbit swings between 30 and 49 AU, sometimes bringing it closer to the Sun than Neptune.
Q 29Which object beyond the belt, discovered in 2005 and 27% more massive than Pluto, forced the IAU to define what a planet is?
Eris
NASA initially called it the tenth planet; a 2010 stellar occultation showed it is actually slightly smaller than Pluto by volume.
Q 30Eris is named after the Greco-Roman goddess of what?
Strife and discord
Its moon Dysnomia is named for the daimon of lawlessness, and the pair were long the most distant known natural objects in the Solar System.