Question:
The Sun produces a continuous spectra. Why is it not just
many many spectral lines from the many many electron 'jumps' possible in
the different atoms?
Replies:
Your first premise is incorrect; however, that does not minimize your
insight that there "should be" absorptions in the continuous Solar
blackbody radiation. The Sun does NOT produce a continuous spectrum of
electromagnetic radiation. Under high resolution there are many "holes" in
the continuum due to absorptions of atoms and molecules in the solar
atmosphere. The same is true of other stars also. And of course
absorptions due to molecules in the Earth's atmosphere if the telescope is
land-based. While these are only observable with a high resolution
spectrometer, astronomers use these spectra to gain a lot of information
about the Sun and stars. For example, comparing the shift in wavelength
from the results obtained in terrestrial laboratories (the Doppler shift)
it is possible to infer the speed at which the star is moving radially
away from the Earth, and from experiments relating the brightness, and
speed of recession it is possible to estimate the distance of the source
(the Hubble correlation). The first of the two web sites below is
especially interesting because you can "dial" a wavelength range and
obtain either a picture of the absorption lines or a table of the values
of the absorptions. One note: the wavelengths are reported in Angstroms,
not nanometers, (1 Ang = 10 nm) so multiply nanometers by (10x).
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