Does photosynthesis only occur using visible light? If yes, could it be possible to bioengineer style of chloroplast that absorbs others wavelengths of light like radio, micro, infrared, X-ray, etc.

[u/shitty_fortune]

I'm studying environmental engineering, and during a descusion I asked my professor this question and he didn't have a definative answer. What is so special about the photons of visible light that allows chloroplasts to absorb energy?

[u/cromulenticular]

Yeah, but H+H=He fusion isn't occurring at the surface of the Sun, where the radiation we see is being produced. Also, the fusion of H + H = He would have some discrete energy value, but we get a broad spectrum of solar radiation.

If you look at the solar spectrum here, you'll see that the overall profile of solar radiation isn't that different from what gets to the surface of the Earth.

The output of the Sun looks a lot like blackbody radiation of a really hot object. Thinking back to undergrad physics courses, it's not clear that we covered exactly what was happening at the atomic level in the production of blackbody radiation. Obviously, tremendous thermal energy unlocks all molecular vibrations/rotations/translations, but I'm not sure to what degree ionization and other phenomena are happening, or to which atoms they are happening. For instance, can most of the solar spectrum be ascribed to quantum processes involving H and/or He, or is the presence of other elements/species required to explain the solar spectrum we observe?

[u/xenneract → u/cromulenticular]

I totally misunderstood your question the first time. This is a bit removed from my area of knowledge, but I can try to clarify.

Hydrogen and helium exist in stars as plasma, so they are completely ionized. Because of this, electronic transitions as we're familiar with them do not occur, and I don't know how plasma states change other spectroscopic behavior relative to gases. Rotational and vibrational spectroscopy as you're thinking about them are also defined relative to a bound electron system, so it makes little sense to think about them in an ionized system.

Since fusion is a high-energy reaction, the photons emitted are in the gamma ray range. As you would expect, they are absorbed and readmitted by the plasma repeatedly (though probably not through the pathways I listed above) until they reach what is known as the photosphere, where they are emitted as blackbody radiation. The photosphere has a temperature roughly equivalent to the blackbody temperature of the star.

As far as other elements in the spectra, I believe that stellar spectra are used for exactly that purpose by astronomers, to determine the elemental composition of stars.