Timeline of solar astronomy
10th century 900–929 — Muhammad ibn Jābir al-Harrānī al-Battānī (Albatenius) discovers that the direction of the Sun's eccentricity is changing
17th century 1613 — Galileo Galilei uses sunspot observations to demonstrate the rotation of the Sun 1619 — Johannes Kepler postulates a solar wind to explain the direction of comet tails
19th century 1802 — William Hyde Wollaston observes dark lines in the solar spectrum 1814 — Joseph Fraunhofer systematically studies the dark lines in the solar spectrum 1834 — Hermann Helmholtz proposes gravitational contraction as the energy source for the Sun 1843 — Heinrich Schwabe announces his discovery of the sunspot cycle and estimates its period to be about a decade 1852 — Edward Sabine shows that sunspot number is correlated with geomagnetic field variations 1859 — Richard Carrington discovers solar flares 1860 — Gustav Kirchhoff and Robert Bunsen discover that each chemical element has its own distinct set of spectral lines 1861 — Gustav Spörer discovers the variation of sun-spot latitudes during a solar cycle, explained by Spörer's law 1863 — Richard Carrington discovers the differential nature of solar rotation 1868 — Pierre Janssen and Norman Lockyer discover an unidentified yellow line in solar prominence spectra and suggest it comes from a new element which they name "helium" 1893 — Edward Maunder discovers the 1645-1715 Maunder sunspot minimum
20th century 1904 — Edward Maunder plots the first sunspot "butterfly diagram" 1906 — Karl Schwarzschild explains solar limb darkening 1908 — George Hale discovers the Zeeman splitting of spectral lines from sunspots 1925 — Cecilia Payne proposes hydrogen is the dominant element of the Sun, not iron 1929 — Bernard Lyot invents the coronagraph and observes the corona with an "artificial eclipse" 1942 — J.S. Hey detects solar radio waves 1949 — Herbert Friedman detects solar X-rays 1960 — Robert B. Leighton, Robert Noyes, and George Simon discover solar five-minute oscillations by observing the Doppler shifts of solar dark lines 1961 — Horace W. Babcock proposes the magnetic coiling sunspot theory 1970 — Roger Ulrich, John Leibacher, and Robert F. Stein deduce from theoretical solar models that the interior of the Sun could act as a resonant acoustic cavity 1975 — Franz-Ludwig Deubner makes the first accurate measurements of the period and horizontal wavelength of the five-minute solar oscillations 1981 — NASA retrieves data from 1978 that shows a comet crashing into the Sun
21st century 2004 — largest solar flare ever recorded occurs
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