I will have to check on this in depth, but… I was not aware the Sun was busily producing elemental oxygen and spewing it into the solar system.
–the Sun does produce elemental oxygen, but that doesn’t wind up in the atmosphere or on the surface of the Earth. I’m no chemist but elemental oxygen is highly reactive if I recall that correctly.(?)
There is oxygen in open space, just not very much of it.

Now I’m intrigued…and I’ll do some actual digging.

(‘Fluff is totally correct that stars that explode, spew out every Element in the periodic table. )

During college, I did a summer internship for a company that made spectrometers to measure the content of the solar wind, but during my first week, the guy I worked for was on vacation, so they had me do research in the department’s library. The most astonishing thing that I learned was the unexpectedly high content of oxygen in the solar wind (unexpected by me, anyway). I did not know the reason for it, but now I learn from Localfluff that it is due to the physics of fusion in the sun’s core.

Thanks, Localfluff. One more mystery solved.