plural noun Astronomy.
the dark lines of the solar spectrum.
Origin of Fraunhofer lines
First recorded in 1830–40; named after J. von Fraunhofer
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
a set of dark lines appearing in the continuous emission spectrum of the sun. It is caused by the absorption of light of certain wavelengths coming from the hotter region of the sun by elements in the cooler outer atmosphere
Word Origin for Fraunhofer lines
named after J. von Fraunhofer (1787–1826), German physicist
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012