60 Fun Facts About Black Hole

What is the boundary around a black hole beyond which nothing can affect an outside observer called?

David Finkelstein gave the modern definition in 1958, calling it a perfect one-way membrane.

What is the name of the supermassive black hole at the centre of the Milky Way?

It weighs in at roughly 4 million Suns and sits about 26,000 light-years from Earth.

In which year was the first-ever image of a black hole published?

The result was announced in six simultaneous press conferences around the world on 10 April.

That first black hole photograph showed the object at the heart of which galaxy?

The galaxy is a supergiant elliptical in Virgo, some 53 million light-years away, with a jet of plasma shooting from its core.

In which year did astronomers unveil the first image of the black hole at the centre of our own galaxy?

The image had been delayed because data from the South Pole Telescope could not be flown out until the austral winter ended.

Which physicist is credited with popularising the term "black hole" in 1967?

He also coined "wormhole" and "quantum foam"; Hawking called him the hero of the black hole story.

Which science journalist used the phrase "black holes" in print as early as January 1964?

Her article reported on a meeting of the American Association for the Advancement of Science in Cleveland.

Which English clergyman-astronomer proposed in 1784 that a body could be too massive for light to escape?

Pierre-Simon Laplace arrived at the same idea independently a few years later.

Karl Schwarzschild found the first exact solution of Einstein's equations while serving in which army?

He did the work in 1915 while on the front in the First World War and died the following year.

Which physicist predicted in 1974 that black holes radiate and slowly evaporate?

The idea was controversial at first; the temperature of the radiation is proportional to the black hole's surface gravity.

How does the temperature of Hawking radiation depend on how heavy the black hole is?

That is why tiny black holes are predicted to blaze away quickly while giant ones are colder than the cosmic microwave background.

Which X-ray source, detected by a 1964 rocket flight, became the first widely accepted black hole?

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.

Kip Thorne collected a year's subscription to which magazine when Hawking conceded their black hole bet?

Hawking had bet against the black hole as insurance: if it did not exist he would win four years of Private Eye.

Which 2014 film sends its crew to planets orbiting a supermassive black hole named Gargantua?

Kip Thorne was executive producer and scientific consultant, and the film won the Oscar for Best Visual Effects.

The 1979 film The Black Hole was the first movie from which studio to receive a PG rating?

At $20 million it was also the studio's most expensive picture to that point, starring Maximilian Schell and Anthony Perkins.

Which 1994 Soundgarden single spent seven weeks atop Billboard's Album Rock Tracks chart?

Written by Chris Cornell, it is considered the band's signature song and topped the chart in Iceland too.

Muse's 2006 single "Supermassive Black Hole" was written by which member of the band?

He said the song added a bit of Prince and Kanye West to the band's sound; it was released on 19 June 2006.

Squeezed into a black hole, the Sun would have a Schwarzschild radius of roughly what size?

Earth's would be about 9 millimetres and the Moon's a tenth of a millimetre.

The no-hair theorem describes a stationary black hole by mass, electric charge and what third number?

It took some 15 years of work after Wheeler's quip that "a black hole has no hair" to nail the theorem down.

Who found the exact solution of Einstein's equations for a rotating black hole in 1963?

Charged, non-rotating black holes are described instead by the Reissner–Nordström metric.

What is the region around a rotating black hole in which it is impossible to stay still called?

Objects can leave it, and via the Penrose process can even come out carrying more energy than they took in.

For a non-rotating black hole, the photon sphere sits at how many times the Schwarzschild radius?

Light skimming that sphere on a tangent is bent completely around the hole and can orbit it more than once.

Roger Penrose won a 2020 Nobel for showing black hole formation is a robust prediction of which theory?

He shared the 1988 Wolf Prize with Hawking for their singularity theorems, and also invented the aperiodic Penrose tiling.

Genzel and Ghez shared the 2020 physics Nobel for finding a supermassive compact object at the centre of what?

Both groups tracked stars whipping around the galactic centre for decades; a black hole was the only explanation.

Andrea Ghez was only the how-manyeth woman to win the Nobel Prize in Physics?

Marie Curie, Maria Goeppert Mayer and Donna Strickland came before her.

Which observatory first directly detected gravitational waves on 14 September 2015?

The signal, GW150914, was announced in February 2016 and won Weiss, Thorne and Barish the 2017 Nobel Prize.

GW150914's black holes of about 36 and 29 solar masses merged into a remnant of roughly how many?

The missing three solar masses were radiated away as gravitational waves in a fraction of a second.

Michell's 1784 letter calculated that a star of the Sun's density but how many times its radius would trap its light?

He also correctly guessed such dark bodies might be detected by their gravitational pull on visible neighbours.

Which astronomer's 1926 book called a star shrunk to its Schwarzschild radius a flaw in Einstein's theory?

He later ridiculed Chandrasekhar's limit for the same reason, calling the implied collapse absurd.

The 1.44-solar-mass limit worked out by a future Nobel laureate applies to what kind of star?

Above the limit, electron degeneracy pressure can no longer hold the star up, so it collapses further.

NASA's Chandra X-ray Observatory, launched in 1999, is named after which physicist?

Raman, the 1930 Nobel laureate, was his uncle.

Chandra was carried into orbit aboard which Space Shuttle?

Mission STS-93 lifted off on 23 July 1999, commanded by Eileen Collins, the first woman to command a shuttle flight.

3C 273, the first quasar ever identified, lies in which constellation?

At magnitude 12.9 it is bright enough to spot with a 6-inch amateur telescope despite being billions of light-years away.

The word "quasar" is a contraction of what phrase?

Hong-Yee Chiu first used the shortened form in Physics Today in May 1964 because the full name was so clumsy.

Roughly how far from Earth is the black hole at the centre of the Milky Way?

At that distance its event horizon spans about 52 million kilometres, yet on the sky it is smaller than a doughnut on the Moon.

Why did Robert Brown add an asterisk to the name "Sgr A*" in 1982?

Brown and Bruce Balick had discovered the compact radio source in February 1974.

Roughly how massive is the Milky Way's central black hole?

Its Schwarzschild radius is only about 12 million kilometres, less than a tenth of the Earth-Sun distance.

How massive did the 2019 imaging campaign measure M87* to be?

Its dark boundary is about 40 billion kilometres across, roughly 2.5 times smaller than the shadow in the famous picture.

What does Pōwehi, the Hawaiian name given to the black hole M87*, mean?

Two of the telescopes in the imaging array sit on Maunakea in Hawaii.

"Spaghettification", a term Hawking popularised, describes what happening to an object near a black hole?

In A Brief History of Time he imagined an astronaut crossing the horizon being "stretched like spaghetti".

In 2004 Hawking conceded a bet to John Preskill with an encyclopedia of which sport?

Hawking later joked that he should perhaps have given Preskill the ashes instead; Kip Thorne, the third party to the bet, declined to concede at the time.

Hawking's A Brief History of Time stayed on the Sunday Times bestseller list for a record how many weeks?

He lived more than 50 years after his motor neurone disease diagnosis, dying in 2018 aged 76.

Gaia BH1, the nearest known system thought to hold a black hole, lies in which constellation?

It is a binary of an ordinary Sun-like star and a stellar-mass black hole about 1,560 light-years away.

Astronomers understand quasars to be what kind of object?

Their stellar-mass cousins inside the Milky Way, also with jets, are called microquasars.

Black holes bigger than stellar ones but smaller than the giants in galactic cores are called what?

They are rarer than either extreme; a candidate called GCIRS 13E was reported orbiting 3 light-years from the galactic centre in 2004.

Hypothetical primordial black holes are thought to have formed when?

They could weigh as little as a hundred-thousandth of a gram at formation.

The hot gas spiralling into a black hole shines most strongly in which part of the spectrum?

Friction heats the material to millions of degrees; disks around young stars, by contrast, glow in the infrared.

The note from the Perseus cluster black hole detected by Chandra in 2003 is how many octaves below middle C?

One oscillation takes 9.6 million years, so no one will ever hear it.

What do astronomers think causes OJ 287 to flare roughly every 12 years?

Its primary is put at some 18 billion solar masses, one of the heaviest black holes measured.

Penrose's 1969 cosmic censorship conjecture proposes that singularities formed by collapse are always what?

It leaves an exterior with strong but finite curvature, from which energy can still be extracted by the Penrose process.

How does the average density inside a supermassive black hole compare with a stellar black hole's?

Volume grows with the cube of the radius but mass only linearly, so the biggest black holes are less dense than water.

Who first argued in 1972 that black holes should have an entropy proportional to their surface area?

Hawking initially argued against the idea before his own 1974 calculation confirmed it.

Katie Bouman led development of which imaging algorithm used to reconstruct the first black hole picture?

It stands for Continuous High-resolution Image Reconstruction using Patch priors and was developed at MIT.

How far away is the galaxy that hosts the first black hole ever photographed?

Charles Messier logged it as a nebula in 1781, in a catalogue meant to stop people mistaking fuzzy objects for comets.

Stellar black holes are typically the remnants of what event?

Only the most massive stars end this way; smaller ones leave white dwarfs or neutron stars behind.

According to Einstein's gravity theory, what lies at the centre of every black hole?

Penrose proved in 1965 that they must form in every black hole, though quantum effects may change the picture.

The star S2 orbits the Milky Way's central black hole in about how many years?

At its 2018 closest approach it hit almost 3% of the speed of light, and its orbit precessed exactly as Einstein predicted.

To out-radiate the cosmic background and truly evaporate, a black hole must weigh less than what?

Such a black hole would be under a tenth of a millimetre across; anything stellar-mass absorbs more from the background radiation than it emits and keeps growing.

Who joined Rainer Weiss and Kip Thorne as the third 2017 physics Nobel laureate for LIGO?

The first detection, GW150914, came from two black holes roughly 30 and 35 solar masses merging about 1.4 billion light-years away.

Which Oppenheimer student co-wrote the 1939 paper that formulated the modern black hole concept?

Their model of an idealised imploding star showed the collapse appearing to freeze at the Schwarzschild radius when viewed from far away.