Timeline of Black Holes
The theory and observation of black holes from 1784 to 2022: John Michell's Newtonian "dark stars", Karl Schwarzschild's solution, Cygnus X-1, Hawking radiation, gravitational waves from merging black holes and the Event Horizon Telescope images.
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- 25 events 1784–2022
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- by claude-opus-5-5
1784: Michell describes stars whose light cannot escape
In a letter to Henry Cavendish, read to the Royal Society in November 1783 and published the next year, John Michell used Newtonian gravity and the particle theory of light to argue that a star as dense as the Sun but over 500 times wider would hold back its own light. He suggested finding such bodies by their pull on visible companions. Now called "dark stars", they were vast Newtonian objects, not black holes in the modern sense.
Wikipedia1796: Laplace suggests the largest stars may be invisible
In the first edition of "Exposition du système du monde", Pierre-Simon Laplace suggested, independently of John Michell, that a sufficiently large star could be invisible because its gravity would stop its light from escaping. He published a mathematical argument in 1799 at Franz Xaver von Zach's request but dropped the idea from later editions. Like Michell's, it treated light as Newtonian particles.
Wikipedia1915: Einstein completes the field equations of general relativity
Albert Einstein presented the final field equations of general relativity to the Prussian Academy of Sciences in November, describing gravity as the curvature of spacetime produced by matter and energy. Black holes in the modern sense are solutions of these equations, although Einstein long doubted that such objects could exist in nature.
Wikipedia1916: Schwarzschild solves Einstein's equations for a spherical mass
While serving in the German army on the Russian front, Karl Schwarzschild found the first exact solution of Einstein's field equations, for a spherical, non-rotating mass, and mailed it to Einstein in December 1915; Johannes Droste found it independently. Schwarzschild died in May of an illness contracted at the front. The Schwarzschild radius, where the solution seemed to break down, was understood as an event horizon only decades later.
Wikipedia1931: Chandrasekhar finds a mass limit for white dwarfs
Combining special relativity with the quantum statistics of electrons, Subrahmanyan Chandrasekhar showed that a white dwarf supported by electron degeneracy pressure cannot be stable above a limiting mass, now put at about 1.4 solar masses; Wilhelm Anderson and Edmund Stoner had found related limits for uniform-density stars. Arthur Eddington rejected the implication that heavier dead stars must keep collapsing.
Wikipedia1939: Oppenheimer and Volkoff find neutron stars' mass limit
Building on work by Richard Tolman, J. Robert Oppenheimer and George Volkoff calculated that neutron stars, held up by neutron degeneracy pressure, have a maximum mass, as white dwarfs do; they put it at about 0.7 solar masses, while later estimates that include nuclear forces lie between about 2 and 3. Above the limit, they concluded, either their model failed or gravitational contraction would not stop.
Wikipedia1939: Oppenheimer and Snyder model a star's continued collapse
In "On Continued Gravitational Contraction", J. Robert Oppenheimer and his student Hartland Snyder used general relativity to follow an idealized star of uniform density and no pressure as it collapsed. They found that a distant observer would see it shrink ever more slowly toward its Schwarzschild radius as its light grew ever redder, while for an observer on the star the collapse would take a finite time. The paper is credited with the modern concept of a black hole.
Wikipedia1958: Finkelstein describes the horizon as a one-way membrane
David Finkelstein showed that the Schwarzschild surface acts as "a perfect unidirectional membrane: causal influences can cross it but only in one direction", the property that now defines an event horizon. Georges Lemaître had shown that the surface is not a true singularity, and Arthur Eddington had published the same coordinate change in 1924, but Finkelstein's reading influenced Lev Landau, Roger Penrose and eventually John Wheeler.
Wikipedia1963: Schmidt measures the large redshift of 3C 273
Using a radio position that Cyril Hazard and colleagues had fixed by lunar occultations at the Parkes radio telescope, Maarten Schmidt found that the starlike object 3C 273 shows hydrogen lines redshifted by 15.8 percent, placing it billions of light-years away and making it far more luminous than any galaxy. In 1964 Edwin Salpeter and Yakov Zeldovich proposed that such quasars are powered by gas falling onto a massive compact object.
Wikipedia1963: Roy Kerr finds the rotating black hole solution
Roy Kerr, a New Zealand mathematician at the University of Texas at Austin, found an exact solution of Einstein's equations for the spacetime around a rotating mass, which proved to describe a spinning black hole; Ezra Newman and colleagues extended it to charged black holes in 1965. Because real black holes are expected to spin and carry almost no charge, the Kerr solution is used to describe astrophysical black holes.
Wikipedia1965: Penrose proves that collapse produces a singularity
Roger Penrose proved that once collapse produces a trapped surface, from which even outgoing light converges, general relativity requires a singularity, where paths of light or matter come to an end, under broad conditions such as non-negative energy density and without assuming symmetry. The result, showing that singularities are a generic outcome of collapse, earned Penrose half of the 2020 Nobel Prize in Physics.
Wikipedia1967: Werner Israel proves the first no-hair theorem
Werner Israel proved that a static black hole without electric charge must be exactly spherical and described by the Schwarzschild solution, fixed by its mass alone. Later work by Israel, Brandon Carter, Stephen Hawking, David Robinson and others extended this to charged and rotating black holes, which depend only on mass, charge and spin, an idea summed up as "black holes have no hair"; a fully general proof is still lacking.
Wikipedia1967: John Wheeler popularizes the name "black hole"
At the annual meeting of the American Association for the Advancement of Science in New York in late December, John Archibald Wheeler called a gravitationally completely collapsed object a "black hole", a name he later said an audience member had suggested at an earlier talk; his stature made it standard. The term was older: Ann Ewing had used it in print in "'Black Holes' in Space", a Science News Letter report of January 18, 1964.
Wikipedia1969: Lynden-Bell proposes black holes in galactic nuclei
In "Galactic Nuclei as Collapsed Old Quasars", Donald Lynden-Bell argued that quasars are powered by gas spiraling through a disk into a massive black hole, and that the dim cores of nearby galaxies hold the dormant black holes of dead quasars. Supermassive black holes, of millions to billions of solar masses, are now accepted to lie at the centers of most galaxies.
Wikipedia1972: Cygnus X-1 identified as a black hole candidate
Louise Webster and Paul Murdin at the Royal Greenwich Observatory and, independently, Charles Thomas Bolton at the University of Toronto measured the orbit of the blue supergiant paired with the X-ray source Cygnus X-1 and found its unseen companion probably too massive to be a neutron star, suggesting a black hole. Discovered by rocket-borne detectors in 1964, the source was generally accepted as most likely a black hole by the end of 1973.
Wikipedia1972: Bekenstein proposes that black holes have entropy
Jacob Bekenstein, a Princeton graduate student of John Wheeler, argued that a black hole has entropy proportional to the area of its event horizon, so that the second law of thermodynamics still holds when matter falls in. Stephen Hawking, who had proved in 1971 that horizon area cannot decrease in classical general relativity, at first rejected the idea, since a body with entropy must have a temperature and radiate.
Wikipedia1974: Hawking predicts that black holes emit radiation
Applying quantum field theory to the curved spacetime outside a black hole, Stephen Hawking calculated in a short paper in Nature that black holes should emit thermal radiation at a temperature inversely proportional to their mass, and so slowly lose mass. The result fixed black hole entropy at one quarter of the horizon area in Planck units. The radiation is far too faint to observe from known black holes and has not been detected.
Wikipedia1974: Balick and Brown discover Sagittarius A*
Using a radio interferometer of the National Radio Astronomy Observatory at Green Bank, West Virginia, Bruce Balick and Robert Brown found a bright, compact radio source at the center of the Milky Way, which Brown later named Sagittarius A*. Donald Lynden-Bell and Martin Rees had predicted in 1971 that the galactic center would hold a massive black hole, and later observations showed that the source marks one.
Wikipedia1976: Hawking poses the black hole information paradox
In "Breakdown of predictability in gravitational collapse", Stephen Hawking argued that because the radiation from an evaporating black hole depends only on its mass, charge and spin, information about what fell in is destroyed, turning pure quantum states into mixed ones in conflict with the unitarity of quantum mechanics. Most physicists now think the information survives, but how remains an open problem in quantum gravity.
Wikipedia1995: Water masers reveal a supermassive black hole
Makoto Miyoshi and colleagues used the Very Long Baseline Array of radio telescopes to track water masers in a thin gas disk orbiting the nucleus of the galaxy NGC 4258 (Messier 106), finding about 36 million solar masses within 0.13 parsecs. No cluster of stars or stellar remnants that dense could survive for long, which made a supermassive black hole by far the most plausible explanation.
Wikipedia1996: Strominger and Vafa count black hole microstates
In "Microscopic Origin of the Bekenstein-Hawking Entropy", Andrew Strominger and Cumrun Vafa used string theory to count the quantum states of a class of extremal, supersymmetric black holes in five dimensions and recovered exactly the entropy that Jacob Bekenstein and Stephen Hawking had derived, one quarter of the horizon area. It was the first microscopic count to reproduce that formula, though only for black holes unlike astrophysical ones.
Wikipedia2002: Star orbits reveal the Milky Way's black hole
Reinhard Genzel's group at the Max Planck Institute for Extraterrestrial Physics traced two-thirds of the orbit of the star S2, which passed within 17 light-hours of Sagittarius A*, ruling out a dense cluster of dark stars or exotic particles as the central mass. Andrea Ghez's group at the University of California, Los Angeles, using the Keck telescopes, reached matching results; the two shared half of the 2020 Nobel Prize in Physics.
Wikipedia2015: LIGO detects gravitational waves from merging black holes
On September 14, both detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) recorded a gravitational-wave signal (GW150914) from two black holes of about 36 and 29 solar masses merging into one of about 62. Announced on February 11, 2016, it was the first direct detection of gravitational waves and of a black hole merger; Rainer Weiss, Barry Barish and Kip Thorne shared the 2017 Nobel Prize in Physics. In 2025 the far clearer signal GW250114 confirmed Stephen Hawking's 1971 theorem that the total horizon area of black holes cannot decrease.
Wikipedia2019: Event Horizon Telescope images the shadow of M87*
The Event Horizon Telescope (EHT), a worldwide network of radio telescopes, released the first image resolving a black hole's shadow: an asymmetric ring of emission around the dark center of M87*, the black hole of about 6.5 billion solar masses in the galaxy Messier 87. Made from April 2017 observations at a wavelength of 1.3 millimeters, it was consistent with general relativity's prediction for a spinning Kerr black hole.
Wikipedia2022: Event Horizon Telescope images Sagittarius A*
The Event Horizon Telescope (EHT) collaboration released an image of Sagittarius A*, the black hole of about 4.3 million solar masses at the center of the Milky Way, showing a ring of emission around a dark shadow like the one it had imaged in the galaxy Messier 87. Made from observations in April 2017, it took five years to produce, partly because the emission around this much smaller black hole varies within minutes.
Wikipedia