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absorption lines/hydrogen balmer lines

I don’t really understand whats happening apart from the excitation of electrons?
I also don’t understand exactly they’re related to stars? Please could someone explain x
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Original post by Htx_x346
I don’t really understand whats happening apart from the excitation of electrons?
I also don’t understand exactly they’re related to stars? Please could someone explain x

Yes it is pretty much just excitation and de-excitation of electrons. There are three named series of emission/absorption lines: the Lyman series is any transition down to/absorption from the n = 1 state, Balmer series is the same but for n = 2, Paschen is the same but for n = 3.

Stars emit a continuous spectrum of photon frequencies, those photons can excite electrons in the surroundings which then de-excite, emitting a specific frequency. This is interstellar space, so "the surroundings" is pretty much just hydrogen gas. Most hydrogen in the universe is in the ground state so you'd need pretty energetic photons to excite it. So if we're observing Balmer emission/absorption lines from somewhere in space then there's something quite energetic going on.
Most of the hydrogen is in its ground state. Because the energy gap between n = 1 and n = 2 is so large, Balmer emission photons (which are less energetic) can pass through unimpeded but Lyman photons would probably excite/ionise the first hydrogen atom they encounter.
(edited 1 year ago)

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