A star does not need to emit visible light to be considered a star. You made that up. According to Wien's law, a cooler star will have peak radiation outside the visible spectrum.
You can do spectral analysis to determine the original emission spectra. The stars have emission and absorption lines at certain wavelengths, and these all get shifted by a certain amount. If it was due to redshift alone, we would know it, i'm pretty sure.
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A star does not need to emit visible light to be considered a star. You made that up. According to Wien's law, a cooler star will have peak radiation outside the visible spectrum.
You can do spectral analysis to determine the original emission spectra. The stars have emission and absorption lines at certain wavelengths, and these all get shifted by a certain amount. If it was due to redshift alone, we would know it, i'm pretty sure.