Neutron Stars Trivia
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49 free Neutron Stars trivia questions with answers — science & nature quiz, new questions added Sep 2026.
This neutron stars trivia quiz covers the collapsed cores of massive stars, the second-densest objects known after black holes. The easy questions handle the basics: what a neutron star is made of, how big it is, the supernova that makes one, why a pulsar pulses, and the famous matchbox and teaspoon comparisons. From there it moves into the discovery story, from Baade and Zwicky's 1933 proposal, less than two years after the neutron itself was found, to the strip-chart signal Jocelyn Bell noticed in 1967 and jokingly labelled LGM-1. The harder half is for astronomy and physics fans: magnetars and the giant flare of 2004, the Crab Pulsar's 33-millisecond period, the Hulse-Taylor binary that proved gravitational waves exist, the 2017 merger GW170817 seen by 70 observatories, the fastest-spinning pulsar in Terzan 5, glitches and starquakes, the Tolman-Oppenheimer-Volkoff limit and the heaviest neutron stars measured. If you enjoyed our black holes or space quizzes, this is the deep dive on the strangest stars in the sky. Every answer was checked against the encyclopaedia entries for neutron stars, pulsars, magnetars and the individual objects named before publishing.
30 of 49 questions with answers and explanations. Play the quiz
Q 01A neutron star is the gravitationally collapsed core of what kind of object?
A massive supergiant
A massive supergiant has a core heavy enough to collapse when its fuel runs out, whereas a star like the Sun simply fades into a white dwarf and never explodes.
Q 02A typical neutron star packs more mass than the Sun into a ball about as wide as what?
A city
A city is the usual comparison: the star is only about 20 kilometres across, and its gravity is strong enough to bend light from its far side into view, so it looks bigger than it really is.
Q 03Which class of objects is the only one denser than neutron stars?
Black holes
Black holes are what a collapsing core becomes when it is too heavy even for packed neutrons to hold up, which leaves a neutron star as the densest object astronomers can observe directly.
Q 04Collisions between neutron stars are thought to forge much of the universe's supply of which element?
Gold
Gold and platinum were among the freshly made heavy elements reported in the glow of the first neutron-star collision ever observed, while carbon, oxygen and iron are forged inside ordinary stars.
Q 05About how many neutron stars are thought to exist in the Milky Way?
Around one billion
Around one billion is the usual estimate, worked out from how many stars have exploded over the galaxy's history, and most of them have long since cooled and gone dark.
Q 06A teaspoon of neutron-star material has a mass roughly 900 times that of which famous structure?
The Great Pyramid of Giza
The Great Pyramid of Giza weighs about six million tonnes, yet a teaspoon outweighs 900 of them because the collapse crushes protons and electrons together into tightly packed neutrons.
Q 07Which pair of astronomers proposed neutron stars in December 1933, less than two years after the neutron was discovered?
Baade and Zwicky
Baade and Zwicky told a meeting of the American Physical Society that an exploding star's core could collapse into a ball of neutrons, 34 years before anyone actually found one.
Q 08Who discovered the neutron in 1932, setting up the idea of neutron stars?
James Chadwick
James Chadwick proved in 1932 that a puzzling radiation others took for gamma rays was really the neutral particle his mentor Ernest Rutherford had predicted years before.
Q 09Jocelyn Bell found the first pulsar as a 'bit of scruff' while reading her radio telescope's output by eye on what?
Paper charts
Paper charts poured off her pen recorders at 96 feet a day and she analysed them all by hand, which is how she spotted a smudge that kept returning from the same patch of sky.
Q 10The first pulsar's discoverers half-jokingly labelled its steady pulses after what?
Little green men
Little green men gave the signal its label, LGM-1, because pulses that steady briefly looked like a beacon from an alien civilisation before a natural cause was found.
Q 11The steadiest pulsars spin so regularly that astronomers compare their timekeeping with what?
Atomic clocks
Atomic clocks are the benchmark, and astronomers now time dozens of these steady pulsars across the sky to catch gravitational waves gently stretching the space in between.
Q 12Which band put a plot of the first pulsar's radio pulses on the cover of its 1979 debut album Unknown Pleasures?
Joy Division
A Joy Division member spotted the stacked pulses in The Cambridge Encyclopaedia of Astronomy, and the plot traces back to Harold Craft's 1970 PhD thesis.
Q 13Which of Bell's colleagues shared the 1974 Nobel Prize in Physics for the discovery of pulsars, while she was left out?
Antony Hewish
Q 21How fast do most magnetars spin, next to ordinary pulsars?
More slowly, once every two to ten seconds
More slowly, once every two to ten seconds, because the colossal magnetic field acts as a brake, carrying off energy and dragging a newborn's rapid spin down within a few thousand years.
Q 22In December 2004 a magnetar's flare from across the galaxy was so bright that its flash bounced off what?
The Moon
The Moon scattered some of the gamma rays back towards a Russian satellite, and for a tenth of a second the blast rivalled a full moon in brightness.
Q 23In 2020 a magnetar in our own galaxy was caught producing which mysterious signal, previously seen only from other galaxies?
Antony Hewish shared the prize with Martin Ryle, and Fred Hoyle protested publicly that Bell, who actually found the signal, had been passed over.
Q 14Jocelyn Bell Burnell gave away her entire $3 million Breakthrough Prize in 2018 to pay for what?
Physics scholarships
Physics scholarships were her choice: the money set up an Institute of Physics fund that helps women, ethnic-minority and refugee students train as research physicists.
Q 15In which part of the UK was pulsar discoverer Bell Burnell born?
Northern Ireland
Northern Ireland was home: she grew up in Lurgan, and staff at the nearby Armagh Observatory encouraged her interest in astronomy when she visited as a girl.
Q 16The explosion that left the Crab Pulsar shone in daylight for weeks in 1054, recorded as a 'guest star' where?
China
China's court astronomers logged the guest star as visible in daylight for 23 days, and their notes on its position let twentieth-century astronomers match it to the Crab Nebula.
Q 17How many times per second does the Crab Pulsar rotate?
About 30
About 30 turns a second, and the spin is slowing by just 38 billionths of a second each day, yet that lost energy is enough to keep the whole Crab Nebula glowing.
Q 18Timing the Crab Pulsar's rapid pulses in 1968 convinced scientists that pulsars were spinning neutron stars rather than what?
Pulsating white dwarfs
Pulsating white dwarfs were the main rival idea, but a star that size cannot throb or spin that quickly without tearing itself apart, which left only something far smaller and denser.
Q 19A magnetar's magnetic field would be lethal from 1,000 kilometres away because it stretches what out of shape?
Atoms
Atoms get squeezed into cigar shapes by a field that strong, and near the star's surface into needles a hundred times longer than wide, so the chemistry that keeps a body alive stops working.
Q 20In 1998 a magnetar flare from 20,000 light-years away made the night-time upper atmosphere behave as if it were what?
Daytime
Daytime conditions returned for five minutes as the gamma rays pushed the electrically charged layer down to its sunlit height, a jolt spotted by Stanford engineers monitoring Navy radio signals to submarines.
Fast radio bursts
Fast radio bursts last only milliseconds and had puzzled astronomers since 2007, so catching one from a magnetar in the Milky Way on 28 April 2020 finally gave them a culprit.
Q 24The fastest-spinning pulsar known rotates roughly how many times every second?
About 700
About 700, or 716 to be exact, which beats the blades of a kitchen blender, and at that rate any star wider than about 30 kilometres would fling its own surface into space.
Q 25Like Jocelyn Bell with the first pulsar, Jason Hessels found a record-fast pulsar in 2004 while he was what?
A graduate student
A graduate student, at McGill in Montreal, which fits a pattern: Bell was one when she spotted the first pulsar, and so was Russell Hulse when he made a find that later won the Nobel Prize.
Q 26Millisecond pulsars are old, yet spin far faster than young ones like the Crab; what spun them up?
Gas from a companion star
Gas from a companion star spills onto the old pulsar and whips it back up to speed, which is why these stars are nicknamed recycled pulsars and are so often found with a partner.
Q 27A 'glitch' in a neutron star is a sudden small change of what kind?
A spin-up
A spin-up of a millionth or less: a glitch interrupts a pulsar's steady slowing, probably when the faster-spinning fluid inside briefly grips the crust and passes on some of its spin.
Q 28In 1974 Hulse and Taylor noticed a pulsar's ticks arriving early, then late, in an eight-hour cycle; what had they found?
The first binary pulsar
The first binary pulsar: its ticks bunched up as it swung toward Earth and spread out as it swung away, betraying an unseen partner that proved to be a second neutron star.
Q 29The Hulse-Taylor pulsar's orbit is slowly shrinking, exactly as predicted by whose theory of gravity?
Albert Einstein
Albert Einstein's general relativity says such a pair must leak energy as gravitational waves, and the orbit duly gets about 75 millionths of a second shorter each year, within half a percent of the forecast.
Q 30Which telescope did Hulse and Taylor use to make their Nobel-winning pulsar discovery in 1974?
The Arecibo 305 m dish
The Arecibo 305 m dish in Puerto Rico was the world's largest for 53 years and the setting for the climax of a 1995 James Bond film, but it collapsed in December 2020 after support cables failed.