The faintest early-Universe galaxy detected and confirmed

A team of scientists led by two UC Davis physicists has detected and confirmed the faintest early-universe galaxy yet using the W. M. Keck Observatory on the summit on Maunakea, Hawaii. This new object, seen as it was about 13 billion years ago, could help astronomers understand the “reionization epoch” when the first stars became visible.
In addition to using the world's most powerful telescope, the team relied on gravitational lensing to see the incredibly faint object born just after the Big Bang
Gravitational lensing is a phenomenon predicted by Einstein. Because gravity can bend the path of light, it’s possible for a distant galaxy to be magnified through the “lens” created by the gravity of another object between it and the viewer. In this case, the detected galaxy was behind the galaxy cluster MACS2129.4-0741, which is massive enough to create three different images of the object. The astronomers were able to show that the three images were of the same galaxy because they showed similar spectra.
It would not have been visible at all if the light from the galaxy was not magnified by the gravitational lens.

https://www.ucdavis.edu/news/astronomers-see-faintest-furthest-galaxy
http://phys.org/news/2016-05-faintest-early-universe-galaxy.html

Paper: http://iopscience.iop.org/article/10.3847/2041-8205/823/1/L14/meta