@petealexharris @G33KatWork @zuthal @samim Yeah, that's right. It's also related to the temperature on the surface, not in the core where the fusion happens, which requires *a lot* more heat and pressure.

The light spectrum of the sun has absorption lines for the various elements too. It's how we get the red/blueshift of distant stars to determine their relative radial velocity from our point of view.