I have a story where a species of the very first (literally first) carbon-based humanoid life (surprise!) that happen to emerge roughly seven billion years ago (their home system were formed twelve billion years ago). Assuming that it's possible that a star with age of around twelve billion years has a system of rocky planets orbiting it (here is the proof), and considering that even ancient galaxies could have similar dust-to-gas ratios as normal "mature" galaxies (just like ours), despite the fact that it was predicted to have lower metal compositions..,
The team’s expectation was that A1689-zD1 would be a more primitive, metal-poor galaxy given its early stage of development. In much the same way that life on Earth began with limited ingredients and evolved into more complex forms, each stellar generation forges elements heavier than hydrogen and helium, which form the building blocks of the following generation. Accordingly, the universe’s very first batch of galaxies is supposed to be pretty basic.
As stated in this page.
The problem is, I just realized that the cosmic background radiation was hotter and more energetic than the way it is now, dating back to 378,000 years after the Big Bang.
Is it possible that at the time, cosmic background radiation is in the visible portion of the electromagnetic spectrum? How warm is space at this time?
To narrow down the possibilities, I require a calculation (for those who are kind enough to work on the math) of how the cosmic background radiation would look like (at which light wavelength, and background temperatures) at this time range:
Twelve billion years ago (the moment that star I mentioned formed) up to seven billion years ago (the moment those carbon-based humanoid species emerge).