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^[1]

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

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

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