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This black hole trivia quiz has 60 free questions with answers and covers the science and the story: how a country clergyman in 1784 first imagined a star whose light could not escape, how Karl Schwarzschild solved Einstein's equations from a First World War trench, why Cygnus X-1 became the first black hole astronomers accepted, and how a planet-sized network of radio dishes finally photographed the shadow of M87* in 2019 and Sagittarius A* in 2022. The easy questions are ones anyone who has watched a space documentary can answer: what the event horizon is, what happens to a star that wanders too close, which 2014 film built its plot around a black hole called Gargantua. The medium ones dig into Hawking radiation, the no-hair theorem, quasars and gravitational waves. The hard and expert ones ask about photon spheres, ergospheres, the Penthouse bet, the baseball encyclopedia and the Hawaiian name given to the first black hole ever imaged. Every answer has been checked against a published reference source, and each question shows its explanation and citation once you have answered, so you can settle the argument as well as start it.
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Q 01What is the boundary around a black hole beyond which nothing can affect an outside observer called?
Event horizon
David Finkelstein gave the modern definition in 1958, calling it a perfect one-way membrane.
Q 02What is the name of the supermassive black hole at the centre of the Milky Way?
Sagittarius A*
It weighs in at roughly 4 million Suns and sits about 26,000 light-years from Earth.
Q 03In which year was the first-ever image of a black hole published?
2019
The result was announced in six simultaneous press conferences around the world on 10 April.
Q 04That first black hole photograph showed the object at the heart of which galaxy?
Messier 87
The galaxy is a supergiant elliptical in Virgo, some 53 million light-years away, with a jet of plasma shooting from its core.
Q 05In which year did astronomers unveil the first image of the black hole at the centre of our own galaxy?
2022
The image had been delayed because data from the South Pole Telescope could not be flown out until the austral winter ended.
Q 06Which physicist is credited with popularising the term "black hole" in 1967?
John Archibald Wheeler
He also coined "wormhole" and "quantum foam"; Hawking called him the hero of the black hole story.
Q 07Which science journalist used the phrase "black holes" in print as early as January 1964?
Ann Ewing
Her article reported on a meeting of the American Association for the Advancement of Science in Cleveland.
Q 08Which English clergyman-astronomer proposed in 1784 that a body could be too massive for light to escape?
John Michell
Pierre-Simon Laplace arrived at the same idea independently a few years later.
Q 09Karl Schwarzschild found the first exact solution of Einstein's equations while serving in which army?
Germany
He did the work in 1915 while on the front in the First World War and died the following year.
Q 10Which physicist predicted in 1974 that black holes radiate and slowly evaporate?
Stephen Hawking
The idea was controversial at first; the temperature of the radiation is proportional to the black hole's surface gravity.
Q 11How does the temperature of Hawking radiation depend on how heavy the black hole is?
Inversely proportional to mass
That is why tiny black holes are predicted to blaze away quickly while giant ones are colder than the cosmic microwave background.
Q 12Which X-ray source, detected by a 1964 rocket flight, became the first widely accepted black hole?
Cygnus X-1
Its companion is a blue supergiant about 7,000 light-years away, and the pair are separated by only a fifth of the Earth-Sun distance.
Q 13Kip Thorne collected a year's subscription to which magazine when Hawking conceded their black hole bet?
Penthouse
Q 21What is the region around a rotating black hole in which it is impossible to stay still called?
Ergosphere
Objects can leave it, and via the Penrose process can even come out carrying more energy than they took in.
Q 22For a non-rotating black hole, the photon sphere sits at how many times the Schwarzschild radius?
1.5
Light skimming that sphere on a tangent is bent completely around the hole and can orbit it more than once.
Q 23Roger Penrose won a 2020 Nobel for showing black hole formation is a robust prediction of which theory?
General relativity
He shared the 1988 Wolf Prize with Hawking for their singularity theorems, and also invented the aperiodic Penrose tiling.
Hawking had bet against the black hole as insurance: if it did not exist he would win four years of Private Eye.
Q 14Which 2014 film sends its crew to planets orbiting a supermassive black hole named Gargantua?
Interstellar
Kip Thorne was executive producer and scientific consultant, and the film won the Oscar for Best Visual Effects.
Q 15The 1979 film The Black Hole was the first movie from which studio to receive a PG rating?
Walt Disney
At $20 million it was also the studio's most expensive picture to that point, starring Maximilian Schell and Anthony Perkins.
Q 16Which 1994 Soundgarden single spent seven weeks atop Billboard's Album Rock Tracks chart?
Black Hole Sun
Written by Chris Cornell, it is considered the band's signature song and topped the chart in Iceland too.
Q 17Muse's 2006 single "Supermassive Black Hole" was written by which member of the band?
Matt Bellamy
He said the song added a bit of Prince and Kanye West to the band's sound; it was released on 19 June 2006.
Q 18Squeezed into a black hole, the Sun would have a Schwarzschild radius of roughly what size?
3 km
Earth's would be about 9 millimetres and the Moon's a tenth of a millimetre.
Q 19The no-hair theorem describes a stationary black hole by mass, electric charge and what third number?
Angular momentum
It took some 15 years of work after Wheeler's quip that "a black hole has no hair" to nail the theorem down.
Q 20Who found the exact solution of Einstein's equations for a rotating black hole in 1963?
Roy Kerr
Charged, non-rotating black holes are described instead by the Reissner–Nordström metric.
Q 24Genzel and Ghez shared the 2020 physics Nobel for finding a supermassive compact object at the centre of what?
The Milky Way
Both groups tracked stars whipping around the galactic centre for decades; a black hole was the only explanation.
Q 25Andrea Ghez was only the how-manyeth woman to win the Nobel Prize in Physics?
Fourth
Marie Curie, Maria Goeppert Mayer and Donna Strickland came before her.
Q 26Which observatory first directly detected gravitational waves on 14 September 2015?
LIGO
The signal, GW150914, was announced in February 2016 and won Weiss, Thorne and Barish the 2017 Nobel Prize.
Q 27GW150914's black holes of about 36 and 29 solar masses merged into a remnant of roughly how many?
62
The missing three solar masses were radiated away as gravitational waves in a fraction of a second.
Q 28Michell's 1784 letter calculated that a star of the Sun's density but how many times its radius would trap its light?
500
He also correctly guessed such dark bodies might be detected by their gravitational pull on visible neighbours.
Q 29Which astronomer's 1926 book called a star shrunk to its Schwarzschild radius a flaw in Einstein's theory?
Arthur Eddington
He later ridiculed Chandrasekhar's limit for the same reason, calling the implied collapse absurd.
Q 30The 1.44-solar-mass limit worked out by a future Nobel laureate applies to what kind of star?
White dwarf
Above the limit, electron degeneracy pressure can no longer hold the star up, so it collapses further.