In a major breakthrough, astronomers have uncovered the never-before-seen close encounter between two astoundingly bright and spectacularly massive galaxies in the early universe. These so-called hyper-luminous starburst galaxies are exceedingly rare at this epoch of cosmic history - near the time when galaxies first formed - and may represent one of the most-extreme examples of violent star formation ever observed. Astronomers at the Cornell University in the US captured these two interacting galaxies, collectively known as ADFS-27, as they began the gradual process of merging into a single, massive elliptical galaxy. An earlier sideswiping encounter between the two helped to trigger their astounding bursts of star formation. The astronomers speculate that this merger may eventually form the core of an entire galaxy cluster. Galaxy clusters are among the most massive structures in the universe. "Finding just one hyper-luminous starburst galaxy is remarkable in itself. Finding two of these rare galaxies in such close proximity is truly astounding," said Dominik Riechers, an astronomer, from the Cornell University. "Considering their extreme distance from Earth and the frenetic star-forming activity inside each, it's possible we may be witnessing the most intense galaxy merger known to date," said Riechers.