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 \sim 2.7 - 3.7 M _ { \odot } yr ^ { -1 } , it contains ~ { } 10 ^ { 8.3 - 8.7 } M _ { \odot } of stars 50-80 Myr old , with stellar metallicity \sim 0.03 - 0.12 Z _ { \odot } .
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 \chi _ { HI } \leq 0.2 and extra ionizing radiation from sources clustered around UDFy-38135539 is necessary .
Finally , we predict that there is a 70 % ( 15 % ) probability of detecting at least 1 such source from JWST ( HST/WFC3 ) observations in a physical radius \sim 0.4 Mpc around UDFy-38135539 .