Confirmation and refutation of very luminous galaxies in the early Universe.

During the first 500 million years of cosmic history, the first stars and galaxies formed, seeding the Universe with heavy elements and eventually reionizing the intergalactic medium. Observations with the James Webb Space Telescope (JWST) have uncovered a surprisingly high abundance of candidates for early star-forming galaxies, with distances (redshifts, z), estimated from multiband photometry, as large as z ≈ 16, far beyond pre-JWST limits. Although such photometric redshifts are generally robust, they can suffer from degeneracies and occasionally catastrophic errors.