While reading about hydrogen on Wikipedia, I read that hydrogen has a purple glow in its plasma state. This confused me because although hydrogen is present in its plasma state on the sun, the sun doesn't appear purple to us (rather, it is yellow-orange). Why is this the case?

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    $\begingroup$ Weird as it is, Sun is actually a decent approximation of a black body. $\endgroup$ – Ivan Neretin Nov 29 '15 at 22:34
  • $\begingroup$ And it is not yellow or orange (or even green). It looks that way through our atmosphere, whose scattering properties cause color separation, but its actual spectrum corresponds closely to what we interpret as white light. $\endgroup$ – Oscar Lanzi Dec 18 '18 at 1:42

The radiation of hydrogen in plasma with low density comes from discrete energy levels, resulting in spectral lines. Those spectral lines can be observed in sunlight, too.

But the sun consists of a plasma with a much higher density. Most photons are the result of a long series of energy exchange inside the sun following the emission of high energy photons and kinetic energy of the nuclear processes. They are part of a continous spectrum as there is not a discrete number of energy levels at the interactions in this high density plasma.

In the photosphere, some of them are absorbed again and result in negative spectral lines (Fraunhofer lines), but the main portion of light remains a continuous spectrum.

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    $\begingroup$ But why is the plasma purple if the main emission line is the red Hα line at 656 nm? $\endgroup$ – ron Nov 29 '15 at 22:34
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    $\begingroup$ Because apparently a second emission gets excited, too. The second line of the Balmer series is at 486 nm, which is blue or turqois. The resulting visual impression of both emissions should be purple. $\endgroup$ – Ariser Nov 30 '15 at 5:54

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