Timeline of solar astronomy

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Timeline of solar astronomy

9th century

• 850 - Ahmad ibn Muhammad ibn Kathīr al-Farghānī (Alfraganus) gives values for the obliquity of the ecliptic, the precessional movement of the apogees of the Sun

10th century

• 900-929 - Muhammad ibn Jābir al-Harrānī al-Battānī (Albatenius) discovers that the direction of the Sun's eccentricity is changing, which in modern astronomy is equivalent to the Earth moving in an elliptic orbit around the Sun
• 950-1000 - Ibn Yunus observes more than 10,000 entries for the Sun's position for many years using a large astrolabe with a diameter of nearly 1.4 metres

11th century

• 1031 - Abū al-Rayhān al-Bīrūnī calculates the distance between the Earth and the Sun in his Canon Mas’udicus

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 and use this fact to explain the solar dark 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 dominate 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 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