They were first observed in 1802 by English physicist William Hyde Wollaston, but are named for the physicist who from about 1814 mapped more than 500 of them and designated the brightest by letters, a system of identification still in use.  
They were first observed in 1802 by English physicist William Hyde Wollaston, but are named for the physicist who from about 1814 mapped more than 500 of them and designated the brightest by letters, a system of identification still in use.  They are caused by selective absorption of the Sun's or star's radiation at specific wavelengths by the various elements existing as gases in its atmosphere.  FTP, name these dark lines in the spectrum of the Sun or other stars.
They were first observed in 1802 by English physicist William Hyde Wollaston, but are named for the physicist who from about 1814 mapped more than 500 of them and designated the brightest by letters, a system of identification still in use.  
Fraunhofer lines