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The observational frontiers for the detection of high‐redshift galaxies have recently been pushed to unimaginable distances with the record‐holding Lyman alpha emitter (LAE) UDFy‐38135539 discovered at redshift  z = 8.6. However, the physical nature and the implications of this discovery have yet to be assessed. By selecting galaxies with observed luminosities similar to UDFy‐38135539 in state‐of‐the‐art cosmological simulations tuned to reproduce the large‐scale properties of LAEs, we bracket the physical nature of UDFy‐38135539: it has a star formation rate ∼2.7–3.7 M ⊙  yr −1 , it contains 10 8.3‐8.7  M ⊙  of stars 50–80 Myr old, with stellar metallicity ∼0.03–0.12 Z ⊙ . For any of the simulated galaxies to be visible as a LAE in the observed range, the intergalactic neutral hydrogen fraction at  z = 8.6 must be  χ H I ≤ 0.2  and extra ionizing radiation from sources clustered around UDFy‐38135539 is necessary. Finally, we predict that there is a 70 per cent (15 per cent) probability of detecting at least one such source from  JWST  ( HST /WFC3) observations in a physical radius ∼0.4 Mpc around UDFy‐38135539.

Ancient giants: on the farthest galaxy at z = 8.6