Detecting hydrogen inside IMC's and GMC's

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Discussion Overview

The discussion centers on the detection of hydrogen within interstellar molecular clouds (IMCs) and giant molecular clouds (GMCs). Participants explore various methods of detecting different forms of hydrogen, including atomic hydrogen (H I), ionized hydrogen (H II), and molecular hydrogen (H2), as well as the conditions affecting their detectability.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants suggest that hydrogen at high temperatures exhibits characteristic spectral lines, while at low temperatures, it can be detected through absorption features when light passes through gas clouds.
  • One participant questions the detection of hydrogen below 100 degrees Kelvin and asks how hydrogen is detected under such conditions.
  • There is a discussion about the three forms of hydrogen in interstellar space: H I (one proton), H II (one proton and one neutron), and H2 (molecular hydrogen), with inquiries about their detectability and temperature preferences.
  • A participant references an article that may provide additional information relevant to the detection of molecular hydrogen.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the detection of hydrogen at low temperatures, and there is no consensus on the conditions required for detecting different forms of hydrogen.

Contextual Notes

Participants highlight limitations in understanding the temperature and density requirements for detecting various hydrogen forms, as well as the potential for opacity in molecular hydrogen leading to the formation of Bok globules.

dougettinger
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I am looking for a brief summary of current hydrogen detection within galaxies.

How are H I and H II detected? Is there a minimum required temperature and/or density ?
How is molecular hydrogen detected? Is this the only form of hydrogen with sufficient density that can become opaque thereby creating Bok globules?

Gas to gas, Doug Ettinger
 
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I can't address the details. However, in general, hydrogen at high temperature has its own characteristic lines in spectra. At low temperature, hydrogen is detected by light shining through it (gas clouds) where the hydrogen lines show up as darkening.
 
I remember reading that hydrogen cannot be detected by emission lines below 100 degrees Kelvin. So below this temperature how is hydrogen detected ?

Hydrogen is in basically three forms in interstellar space: only one proton, one proton and one neutron, and a hydrogen molecule, H2. Are all these forms equally detectable ? Does each type of isotope prefer a certain temperature range?

Regards, Doug Ettinger
 

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