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50 free Neutron Stars trivia questions with answers — science & nature quiz, new questions added Aug 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 50 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
Stars that end up as neutron stars typically start out with 10 to 25 times the mass of the Sun.
Q 02Roughly what is the radius of a typical neutron star?
About 10 kilometres
That is roughly the size of a city, yet the star packs in around 1.4 times the mass of the Sun.
Q 03Which class of objects is the only one denser than neutron stars?
Black holes
Neutron stars are the second-smallest and second-densest known class of stellar objects.
Q 04What kind of event compresses a stellar core into a neutron star?
A supernova explosion
The core is squeezed past white-dwarf density all the way to the density of atomic nuclei.
Q 05About how many neutron stars are thought to exist in the Milky Way?
Around one billion
The estimate comes from counting how many stars have gone supernova, and most of them have long since cooled and gone dark.
Q 06A normal-sized matchbox of neutron-star material would weigh roughly how much?
3 billion tonnes
That is the same weight as a half-cubic-kilometre chunk of the Earth's surface, a cube about 800 metres on each edge.
Q 07A teaspoon of neutron-star material has a mass roughly 900 times that of which famous structure?
The Great Pyramid of Giza
At the same density the entire Earth would fit into a sphere 305 metres across, about the size of the Arecibo Telescope.
Q 08Which pair of physicists proposed the existence of neutron stars at a December 1933 meeting, less than two years after the neutron was discovered?
Baade and Zwicky
They also correctly proposed that the release of gravitational binding energy is what powers a supernova.
Q 09Who discovered the neutron in 1932, setting up the idea of neutron stars?
James Chadwick
Two Caltech astronomers proposed neutron stars less than two years later.
Q 10Which graduate student first noticed the signal of the first pulsar in 1967 while analysing chart recordings from a Cambridge radio telescope?
Jocelyn Bell
She sometimes reviewed as much as 96 feet of paper chart data per night, and had helped build the telescope over the previous two years.
Q 11What playful nickname did the discoverers give the first pulsar signal?
LGM-1
It stood for 'little green men', because the regularity briefly suggested an alien beacon, until a second pulsar turned up elsewhere in the sky.
Q 12How long is the period of PSR B1919+21, the first pulsar ever discovered?
About 1.337 seconds
It sits in the constellation Vulpecula and was originally catalogued as CP 1919, for Cambridge Pulsar.
Q 13Which band put a plot of the first pulsar's radio pulses on the cover of its 1979 debut album Unknown Pleasures?
Joy Division
The image was created by radio astronomer Harold Craft and has since become one of the most reproduced graphics in music.
Q 21Which two scientists proposed the existence of magnetars in 1992?
Duncan and Thompson
They were trying to explain the mysterious transient gamma-ray sources now known as soft gamma repeaters.
Q 22Compared with ordinary radio pulsars, how fast do most observed magnetars rotate?
More slowly, once every two to ten seconds
Typical neutron stars seen as radio pulsars turn one to ten times per second.
Q 23On 27 December 2004, radiation from a starquake on which magnetar produced the brightest event ever seen from outside the Solar System up to that time?
SGR 1806-20
Q 14Which of Bell's colleagues shared the 1974 Nobel Prize in Physics for the discovery of pulsars, while she was left out?
Antony Hewish
Fred Hoyle publicly argued that Bell should have been a co-recipient; the omission is still debated.
Q 15What did Bell Burnell do with the $3 million from her 2018 Special Breakthrough Prize?
Endowed a scholarship fund for under-represented students
The fund, run by the Institute of Physics, helps female, minority and refugee students become research physicists.
Q 16In which part of the UK was pulsar discoverer Bell Burnell born?
Northern Ireland
She grew up in Lurgan, County Armagh, and was encouraged by staff at the nearby Armagh Observatory.
Q 17The Crab Pulsar is the remnant of a supernova that was widely observed on Earth in which year?
1054
Discovered in 1968, it was the first pulsar to be connected with a supernova remnant.
Q 18How many times per second does the Crab Pulsar rotate?
About 30
Its 33-millisecond period is lengthening by 38 nanoseconds a day as energy pours out in the pulsar wind.
Q 19The measurement of the Crab Pulsar's 33-millisecond period in 1968 finally convinced scientists that pulsars were rotating neutron stars rather than what?
Pulsating white dwarfs
Lovelace and colleagues made the measurement using the Arecibo Observatory.
Q 20What is a magnetar?
A neutron star with an extremely powerful magnetic field
Their fields are roughly a hundred million times stronger than any man-made magnet, and decay after about 10,000 years.
In a tenth of a second it released more energy than the Sun puts out in 150,000 years, and it briefly expanded Earth's ionosphere.
Q 24Which cosmic phenomenon has been linked to magnetars by 2020 findings from Australia's ASKAP array?
Fast radio bursts
Out of roughly 3,000 known neutron stars, only 31 were confirmed magnetars as of January 2021.
Q 25PSR J1748-2446ad, the fastest-spinning pulsar known, rotates roughly how many times per second?
About 716
Its equator moves at roughly a quarter of the speed of light, more than 70,000 kilometres per second.
Q 26The fastest-spinning known pulsar lives in which globular cluster in Sagittarius?
Terzan 5
The cluster is about 18,000 light-years away, and the pulsar has a bloated companion that eclipses it regularly.
Q 27For 24 years the spin record belonged to PSR B1937+21, discovered by Don Backer in 1982 as the first example of which type of object?
Millisecond pulsar
It spins 642 times a second, a value that placed fundamental limits on how big and heavy neutron stars can be.
Q 28A 'glitch' in a neutron star is a sudden small change of what kind?
A spin-up
One explanation is a starquake: as the crust cracks and the star becomes more spherical, conservation of angular momentum speeds it up.
Q 29Which 1974 discovery by Hulse and Taylor consisted of two neutron stars orbiting each other?
The first binary pulsar
Its orbit has decayed exactly as general relativity predicts for gravitational-wave emission, earning the pair the 1993 Nobel Prize.
Q 30How long does it take the two neutron stars of the Hulse-Taylor system to orbit each other?
About 7.75 hours
At closest approach they are only about 1.1 solar radii apart, and their periastron swings round by 4.2 degrees a year.