All Questions
Tagged with electromagnetic-spectrum spectroscopy
8
questions
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121
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Why is the H-alpha line slightly shorter in wavelength (656.28 nm) in air than in vacuum (656.46 nm)? Shouldn't it be longer?
Perhaps this is a question better suited for Physics SE, but since the H-alpha line is so important in astronomy, I'm posting this here....
I would, naively, assume that wavelengths would be longer, ...
- 5,307
6
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1
answer
402
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Natural line width from absorption lines
Emission lines have a certain natural width. Due to the uncertainty principle systems that spontaneously decay or produce radiation have a fundamental energy blur, and their radiation has a ...
- 849
4
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2
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793
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Does the luminosity of a star have the form of a Planck curve?
Figure shows the intensity of the radiant energy emitted from stars A and B over a unit time according to the wavelength. The area between the graph and the horizontal axis is S and 4S, respectively.
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3
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1
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How are absorption cross sections calculated?
I would like to develop a more intuitive understanding of cross sections, in the context of radiative transfer.
I understand that a cross section, $\sigma_\nu$, is a measure of a given atom/molecule's ...
- 1,386
1
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1
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How is the H II 'region' directly detectable? By Compton or Thomson free-particle scattering? At what wavelengths?
The Wikipedia page on H II regions says that they are 'indirectly' detectable by the detection of doubly-ionized oxygen atoms mixed in.... (I am presuming atoms, not diatomic molecules...)
But are ...
- 5,307
4
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3
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371
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Spectrum of stars
If some specific metal is shown in a star's spectrum, does it indicate that the star has that specific metal? For example, the Sun, a G2 star, shows medium strength of Ionised Calcium in its spectrum, ...
- 1,296
2
votes
1
answer
307
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Missing line in solar spectrum
Referring to this answer to What's the rationale behind the false colours in solar observation photographs? which includes the table from Wikipedia's Fraunhofer lines:
In the Table of wavelengths ...
0
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1
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204
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Do free protons and neutrons absorb much radiation? To affect astronomers' observations? If so, at what wavelength(s)?
In a plasma, or wherever, do the completely ionized nuclei commonly absorb much EM radiation? Or any free neutrons or protons? Can astronomers detect this? Enough so that astronomers take it into ...
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