  thumb|right|320px|solar spectrum with fraunhofer lines as it appears visually. thumb|right|320px|spectrum of blue sky. dips are present at the fraunhofer line wavelengths. in physics and optics, the fraunhofer lines are a set of spectral lines named after the german physicist joseph von fraunhofer (1787â1826) . the lines were originally observed as dark features (absorption lines) in the optical spectrum of the sun. ==discovery== in 1802, the english chemist william hyde wollastonmelvyn c. usselman: william hyde wollaston encyclopedia britannica, retrieved 31 march 2013 was the first person to note the appearance of a number of dark features in the solar spectrum.william hyde wollaston (1802) "a method of examining refractive and dispersive powers, by prismatic reflection," philosophical transactions of the royal society, 92: 365-380; see especially p. 378. in 1814, fraunhofer independently rediscovered the lines and began a systematic study and careful measurement of the wavelength of these features. in all, he mapped over 570 lines, and designated the principal features with the letters a through k, and weaker lines with other letters. joseph fraunhofer (1814 - 1815) "bestimmung des brechungs- und des farben-zerstreuungs - vermÃ¶gens verschiedener glasarten, in bezug auf die vervollkommnung achromatischer fernrÃ¶hre" (determination of the refractive and color-dispersing power of different types of glass, in relation to the improvement of achromatic telescopes), denkschriften der kÃ¶niglichen akademie der wissenschaften zu mÃ¼nchen (memoirs of the royal academy of sciences in munich), 5: 193-226; see especially pages 202-205 and the plate following page 226. modern observations of sunlight can detect many thousands of lines. about 45 years later kirchhoff and bunsensee: * gustav kirchhoff (1859) "ueber die fraunhofer'schen linien" (on fraunhofer's lines), monats
Astrochemistry Atomic_physics Spectroscopy