All Questions
Tagged with electromagnetic-spectrum observational-astronomy
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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, ...
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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 ...
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What would it take to view "the whole EM spectrum"?
I know the EM spectrum goes off both ends, but nearly everything anyone has bothered to use it for has wavelengths between $10^8$m (ELF) and $10^{-12}$m or so (gamma rays). So for the purposes of this ...
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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 ...
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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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