Fraunhofer Lines
A set of dark absorption lines in the solar spectrum caused by chemical element absorption in the Sun's outer atmosphere.
Governing formula
E = h ν = E_upper - E_lower
SI unit
nm
In depth
First mapped by Joseph von Fraunhofer in 1814. Act as atomic fingerprints, establishing elemental composition of stellar atmospheres.
Examples in the real world
The prominent sodium D doublet absorption lines at 589.0 nm and 589.6 nm in sunlight.