What process confirmed the immense distance of galaxy GN-z11 by measuring the exact shift in its light spectrum?

Spectroscopic analysis

While initial discovery of distant galaxy candidates often utilizes broad photometric surveys, which measure overall brightness through various color filters, definitive proof of their vast distance relies on a more precise technique. Spectroscopic analysis involves splitting the light received from the object into its constituent colors, much like a prism, creating a spectrum. By precisely measuring the location of specific spectral lines within this spectrum, astronomers can calculate the exact shift—the redshift—of the light caused by the universe's expansion. This provides a robust and accurate measurement of the object's distance and look-back time, which was crucial for confirming the record-breaking status of GN-z11.