Timeline of knowledge about galaxies, clusters of galaxies, and large-scale structure

The following is a timeline of galaxies, clusters of galaxies, and large-scale structure of the universe.

Pre-20th century

  • 5th century BC — Democritus proposes that the bright band in the night sky known as the Milky Way might consist of stars.
  • 4th century BC — Aristotle believes the Milky Way to be caused by "the ignition of the fiery exhalation of some stars which were large, numerous and close together" and that the "ignition takes place in the upper part of the atmosphere, in the region of the world which is continuous with the heavenly motions".
  • 964 — Abd al-Rahman al-Sufi (Azophi), a Persian astronomer, makes the first recorded observations of the Andromeda Galaxy and the Large Magellanic Cloud in his Book of Fixed Stars, and which are the first galaxies other than the Milky Way to be observed from Earth.
  • 11th century — Al-Biruni, another Persian astronomer, describes the Milky Way galaxy as a collection of numerous nebulous stars.
  • 11th century — Alhazen (Ibn al-Haytham), an Arabian astronomer, refutes Aristotle's theory on the Milky Way by making the first attempt at observing and measuring the Milky Way's parallax, and he thus "determined that because the Milky Way had no parallax, it was very remote from the Earth and did not belong to the atmosphere".
  • 12th century — Avempace (Ibn Bajjah) of Islamic Spain proposes the Milky Way to be made up of many stars but that it appears to be a continuous image due to the effect of refraction in the Earth's atmosphere.
  • 14th century — Ibn Qayyim al-Jawziyya of Syria proposes the Milky Way galaxy to be "a myriad of tiny stars packed together in the sphere of the fixed stars" and that these stars are larger than planets.
  • 1521 — Ferdinand Magellan observes the Magellanic Clouds during his circumnavigating expedition.
  • 1610 — Galileo Galilei uses a telescope to determine that the bright band on the sky, the "Milky Way", is composed of many faint stars.
  • 1612 — Simon Marius using a moderate telescope observes Andromeda and describes as a "flame seen through horn".
  • 1750 — Thomas Wright discusses galaxies and the flattened shape of the Milky Way and speculates nebulae as separate.
  • 1755 — Immanuel Kant drawing on Wright's work conjectures our galaxy is a rotating disk of stars held together by gravity, and that the nebulae are separate such galaxies; he calls them Island Universes.
  • 1774 — Charles Messier releases a preliminary list of 45 Messier objects, three of which turn out to be the galaxies including Andromeda and Triangulum. By 1781 the final published list grows to 103 objects, 34 of which turn out to be galaxies.
  • 1785 — William Herschel carried the first attempt to describe the shape of the Milky Way and the position of the Sun in it by carefully counting the number of stars in different regions of the sky. He produced a diagram of the shape of the galaxy with the solar system close to the center.
  • 1845 — Lord Rosse discovers a nebula with a distinct spiral shape.

Early 20th century

Mid-20th century

  • 1953 — Gérard de Vaucouleurs discovers that the galaxies within approximately 200 million light-years of the Virgo Cluster are confined to a giant supercluster disk.
  • 1954 — Walter Baade and Rudolph Minkowski identify the extragalactic optical counterpart of the radio source Cygnus A.
  • 1959 — Hundreds of radio sources are detected by the Cambridge Interferometer which produces the 3C catalogue. Many of these are later found to be distant quasars and radio galaxies.
  • 1960 — Thomas Matthews determines the radio position of the 3C source 3C 48 to within 5".
  • 1960 — Allan Sandage optically studies 3C 48 and observes an unusual blue quasistellar object.
  • 1962 — Cyril Hazard, M. B. Mackey, and A. J. Shimmins use lunar occultations to determine a precise position for the quasar 3C 273 and deduce that it is a double source.
  • 1962 — Olin Eggen, Donald Lynden-Bell, and Allan Sandage theorize galaxy formation by a single (relatively) rapid monolithic collapse, with the halo forming first, followed by the disk.
  • 1963 — Maarten Schmidt identifies the redshifted Balmer lines from the quasar 3C 273.
  • 1973 — Jeremiah Ostriker and James Peebles discover that the amount of visible matter in the disks of typical spiral galaxies is not enough for Newtonian gravitation to keep the disks from flying apart or drastically changing shape.
  • 1973 — Donald Gudehus finds that the diameters of the brightest cluster galaxies have increased due to merging, the diameters of the faintest cluster galaxies have decreased due to tidal distention, and that the Virgo cluster has a substantial peculiar velocity.
  • 1974 — B. L. Fanaroff and J. M. Riley distinguish between edge-darkened (FR I) and edge-brightened (FR II) radio sources.
  • 1976 — Sandra Faber and Robert Jackson discover the Faber-Jackson relation between the luminosity of an elliptical galaxy and the velocity dispersion in its center. In 1991 the relation is revised by Donald Gudehus.
  • 1977 — R. Brent Tully and Richard Fisher publish the Tully–Fisher relation between the luminosity of an isolated spiral galaxy and the velocity of the flat part of its rotation curve.
  • 1978 — Steve Gregory and Laird Thompson describe the Coma supercluster.
  • 1978 — Donald Gudehus finds evidence that clusters of galaxies are moving at several hundred kilometers per second relative to the cosmic microwave background radiation.
  • 1978 — Vera Rubin, Kent Ford, N. Thonnard, and Albert Bosma measure the rotation curves of several spiral galaxies and find significant deviations from what is predicted by the Newtonian gravitation of visible stars.
  • 1978 — Leonard Searle and Robert Zinn theorize that galaxy formation occurs through the merger of smaller groups.

Late 20th century

Early 21st century

See also