The 27 papers that built modern astronomy
A reading guide in the order the papers were published, from 1912 to 2020. Each entry says in one line why it matters, then links to our plain-English summary and to the original.
By The Orbital Record editorial teamLast reviewed
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1912
1 of 27
Leavitt and Pickering, Harvard College Observatory Circular, 173, 1-3
Henrietta Leavitt's Law: The Key to Cosmic Distances
Found in 1912 that brighter Cepheid stars pulse more slowly. Henrietta Leavitt's law became the first standard candle for measuring cosmic distances.
1915
2 of 27
Einstein, Sitzungsberichte der Königlich Preussischen Akademie der Wissenschaften (Berlin), 844-847
Einstein's 1915 Paper: The Field Equations of General Relativity
Completed general relativity in 1915. Albert Einstein's four-page paper on the field equations of gravitation: what it says, how it was tested.
1916
3 of 27
Schwarzschild, Sitzungsberichte der Königlich Preussischen Akademie der Wissenschaften zu Berlin, 189-196
Schwarzschild's Solution: The Birth of the Black Hole
Found in 1916 the first exact solution of Einstein's equations, with the radius now known as a black hole's horizon. Karl Schwarzschild's paper, explained.
1925
4 of 27
Payne, Harvard Observatory Monographs No. 1 (PhD thesis, Radcliffe College)
Cecilia Payne's Thesis: Stars Are Made of Hydrogen
Showed in 1925 that stars are mostly hydrogen and helium. Cecilia Payne's PhD thesis decoded stellar spectra and revealed what the universe is made of.
1927
5 of 27
Lemaître, Annales de la Société Scientifique de Bruxelles, A47, 49-59
Georges Lemaître: The First Case for an Expanding Universe
Derived in 1927 that the universe is expanding and that galaxies recede in proportion to distance. Georges Lemaître's paper, two years before Hubble.
1929
6 of 27
Hubble, Proceedings of the National Academy of Sciences, 15, 168-173
Hubble's Law: The Discovery That the Universe Is Expanding
Showed in 1929 that galaxies recede faster the farther away they are. Edwin Hubble's six-page paper, its numbers, the Lemaître credit, and the original.
1931
7 of 27
Chandrasekhar, The Astrophysical Journal, 74, 81
The Chandrasekhar Limit: How Massive a White Dwarf Can Be
Showed in 1931 that white dwarfs have a maximum mass. Subrahmanyan Chandrasekhar's limit, now about 1.4 Suns, decides which dead stars collapse further.
1933
8 of 27
Zwicky, Helvetica Physica Acta, 6, 110-127
Zwicky's Dark Matter: The First Hint of Invisible Mass
Found in 1933 that the Coma galaxy cluster needs far more mass than its stars show, and named it dark matter. Fritz Zwicky's paper, explained.
1939
9 of 27
Bethe, Physical Review, 55, 434-456
Hans Bethe: How Nuclear Fusion Makes the Stars Shine
Explained in 1939 why stars shine: Hans Bethe worked out the fusion reactions, the proton-proton chain and the CNO cycle, that turn hydrogen into helium.
1953
10 of 27
Miller, Science, 117, 528-529
The Miller-Urey Experiment: Making Life's Building Blocks
Showed in 1953 that sparks in methane, ammonia, hydrogen and water vapor make amino acids. Stanley Miller's flask experiment founded prebiotic chemistry.
1957
11 of 27
Burbidge et al., Reviews of Modern Physics, 29, 547-650
The B2FH Paper: How Stars Make the Chemical Elements
Explained in 1957 how stars forge almost every element heavier than helium. Burbidge, Burbidge, Fowler and Hoyle set out eight nucleosynthesis processes.
1965
12 of 27
Penzias and Wilson, The Astrophysical Journal, 142, 419-421
Cosmic Microwave Background: Penzias and Wilson's Discovery
Detected in 1965 a faint 3.5 K microwave glow from every direction. Penzias and Wilson's two-page paper found the afterglow of the Big Bang.
1968
13 of 27
Hewish et al., Nature, 217, 709-713
Jocelyn Bell's Pulsar: The First Neutron Star Signal
Reported in 1968 the first pulsar, a radio source ticking every 1.337 seconds. Found by Jocelyn Bell, it proved that neutron stars exist.
1970
14 of 27
Rubin and Jr., The Astrophysical Journal, 159, 379-403
How Vera Rubin Found Dark Matter: The Paper Explained
Measured in 1970 that Andromeda's outer regions spin as fast as its inner ones, a sign of unseen mass. Vera Rubin and Kent Ford's rotation curve paper.
1974
15 of 27
Hawking, Nature, 248, 30-31
Hawking Radiation: How Black Holes Slowly Evaporate
Showed in 1974 that black holes glow faintly and evaporate, ending in a burst. Stephen Hawking's two-page Nature letter on Hawking radiation, explained.
1975
16 of 27
Hulse and Taylor, The Astrophysical Journal Letters, 195, L51-L53
Hulse-Taylor Binary Pulsar: The First Gravitational Wave Clue
Discovered in 1974 a pulsar orbiting a neutron star every 7.75 hours, later the first evidence of gravitational waves. Hulse and Taylor's Nobel paper.
1980
17 of 27
Alvarez et al., Science, 208, 1095-1108
The Alvarez Hypothesis: An Asteroid Killed the Dinosaurs
Found in 1980 a spike of iridium where the Cretaceous ends. Luis and Walter Alvarez proposed that a 10 km asteroid caused the extinction of the dinosaurs.
1981
18 of 27
Guth, Physical Review D, 23, 347-356
Cosmic Inflation: Alan Guth's Fix for the Big Bang
Proposed in 1981 that the infant universe expanded exponentially for a brief moment. Alan Guth's inflation paper, its puzzles, its flaw and its tests.
1992
19 of 27
Smoot et al., The Astrophysical Journal, 396, L1-L5
COBE's Cosmic Ripples: The Seeds of Every Galaxy
Detected in 1992 the first ripples in the cosmic microwave background, about 30 millionths of a degree. George Smoot's COBE result and why it won a Nobel.
1995
20 of 27
Mayor and Queloz, Nature, 378, 355-359
51 Pegasi b: The First Planet Around a Sun-Like Star
Found in 1995 the first planet orbiting a Sun-like star. Mayor and Queloz detected 51 Pegasi b, a hot Jupiter that circles its star every 4.23 days.
1997
21 of 27
Adams and Laughlin, Reviews of Modern Physics, 69, 337-372
A Dying Universe: The Five Ages of the Universe Explained
Mapped the universe's future into eras, from the age of stars to a dark era beyond 10100 years. Fred Adams and Gregory Laughlin's 1997 review, explained.
1998
22 of 27
Riess et al., The Astronomical Journal, 116, 1009-1038
The Accelerating Universe: Supernovae Reveal Dark Energy
Showed in 1998 that cosmic expansion is speeding up. Adam Riess and the High-Z team used distant supernovae. What they found, and the original paper.
1999
23 of 27
Perlmutter et al., The Astrophysical Journal, 517, 565-586
Supernova Cosmology Project: 42 Supernovae and Dark Energy
Showed with 42 distant supernovae that the cosmological constant is positive and expansion is accelerating. Saul Perlmutter's Nobel paper, explained.
2016
24 of 27
LIGO Scientific Collaboration and Virgo Collaboration, Physical Review Letters, 116, 061102
First Gravitational Wave Detection: LIGO's GW150914 Paper
Detected gravitational waves for the first time, from two black holes merging 1.3 billion light-years away. The 2016 LIGO-Virgo GW150914 paper.
2017
25 of 27
LIGO Scientific Collaboration and Virgo Collaboration, Physical Review Letters, 119, 161101
GW170817: The Neutron Star Merger Seen in Waves and Light
Detected in 2017 two neutron stars merging 40 megaparsecs away, also seen as a gamma-ray burst and a kilonova. The LIGO-Virgo GW170817 discovery paper.
2019
26 of 27
Event Horizon Telescope Collaboration, The Astrophysical Journal Letters, 875, L1
First Image of a Black Hole: The M87* Shadow Explained
Captured in 2019 the first image of a black hole: a ring of light around the shadow of M87*, 6.5 billion Suns. The Event Horizon Telescope's paper.
2020
27 of 27
Planck Collaboration, Astronomy & Astrophysics, 641, A6
Planck 2018 Results: The Universe Is 13.8 Billion Years Old
Measured the universe's age at 13.787 billion years and its expansion rate at 67.4 km/s/Mpc. The Planck Collaboration's final 2018 parameters, explained.