I'm not a scientist, but I imagine that they would use the emission spectrum[0] of the various elements. Perhaps they could sample the spectrum of all of the st

I'm not a scientist, but I imagine that they would use the emission spectrum[0] of the various elements. Perhaps they could sample the spectrum of all of the stars and that might give a reasonable approximation. [0] http://en.wikipedia.org/wiki/Emission_spectrum http://en.wikipedia.org/wiki/Emission_spectrum