Fraunhofer lines


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Related to Fraunhofer lines: Fraunhofer spectrum

Fraunhofer lines

(froun`hôfər): see sunsun,
intensely hot, self-luminous body of gases at the center of the solar system. Its gravitational attraction maintains the planets, comets, and other bodies of the solar system in their orbits.
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Fraunhofer lines

(frown -hoh-fer) Absorption lines in the solar (photospheric) spectrum, first studied in detail by Joseph von Fraunhofer in 1814. He cataloged over 500 lines and labeled the more striking ones with letters. Over 25 000 lines have now been identified. The most prominent lines at visible wavelengths are due to the presence of singly ionized calcium, neutral hydrogen, sodium, and magnesium; many weaker lines are due to iron. The strength of a particular line depends not only on the quantity of the element present but also on the degree of ionization and level of excitation of its atoms. By isolating an individual strong line it is possible, by virtue of its residual intensity due to the reemission of radiation in the chromosphere, to observe the chromosphere in the light of the element concerned. See spectroheliogram. See also D lines; H and K lines; photosphere.

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 lineWavelength (microns)Chemical element
A ...............0.7610
B ...............0.6870
C ...............0.656Hα
D ...............0.589Na
E ...............0.527Fe
F ...............0.486Hβ
G ...............0.431Ca
H1 ...............0.397Ca
H ...............0.393Ca

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.

Fraunhofer lines

[′frau̇n‚hōf·ər ‚līnz]
(spectroscopy)
The dark lines constituting the Fraunhofer spectrum.
References in periodicals archive ?
Within the gaseous models of the Sun, the absence of Fraunhofer lines in the K-corona is explained by scattering photospheric light with high energy electrons (see e.
The Fraunhofer lines are being broadened by electrons in the K-corona, but emission lines from the same region of the solar atmosphere, namely in the Ecorona, remain visible and sharp.
Still, the continuous nature of its emission, and the absence of Fraunhofer lines in the inner corona has been well documented [2-10].
In the end, the simplest means of accounting for the continuous emission observed in the K-corona, the absence of overlying Fraunhofer lines, and the presence of sharp emission lines in this same region of the solar atmosphere, is to invoke a condensed matter model of the Sun [18-20].

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