Fraunhofer Lines

Fraunhofer lines (froun`hôfər): see sun.

---

Fraunhofer lines

In astronomical spectroscopy, dark lines in a star's spectrum caused by selective absorption of its radiation at specific wavelengths by the various chemical elements in its atmosphere. First observed in 1802, they are named for the German physicist Joseph von Fraunhofer (1787–1826), who from c. 1814 plotted over 500 of them and designated the brightest with the first few letters of the alphabet. About 25,000 Fraunhofer lines are known to exist in the Sun's spectrum, between the wavelengths of 2,950 and 10,000 angstroms.

---

Fraunhofer lines [′frau̇n‚hōf·ər ‚līnz]

(spectroscopy)

The dark lines constituting the Fraunhofer spectrum.

---

Fraunhofer Lines 

absorption lines in the solar spectrum. Fraunhofer lines were first observed in 1802 by the British physicist W. H. Wollaston (1766–1828). They were detected and described in detail by J. von Fraunhofer in 1814 and were later correctly explained by G. R. Kirchhoff.

More than 20,000 Fraunhofer lines have been observed in the

Table 1. Some Fraunhofer lines
Symbol for line	Wavelength (microns)	Chemical element
A ...............	0.761	0
B ...............	0.687	0
C ...............	0.656	Hα
D ...............	0.589	Na
E ...............	0.527	Fe
F ...............	0.486	Hβ
G ...............	0.431	Ca
H1 ...............	0.397	Ca
H ...............	0.393	Ca

infrared, ultraviolet, and visible regions of the solar spectrum; many have been identified with the spectral lines of known chemical elements. The most intense Fraunhofer lines in the visible region are given in Table 1.