Our ability to study the most remote supernova explosions , crucial for the understanding of the evolution of the high-redshift universe and its expansion rate , is limited by the light collection capabilities of telescopes .
However , nature offers unique opportunities to look beyond the range within reach of our unaided instruments thanks to the light-focusing power of massive galaxy clusters .
Here we report on the discovery of one of the most distant supernovae ever found , at redshift , z = 1.703 .
Due to a lensing magnification factor of 4.3 \pm 0.3 , we are able to measure a lightcurve of the supernova , as well as spectroscopic features of the host galaxy with a precision comparable to what will otherwise only be possible with future generation telescopes .