Astronomers have discovered a new kind of galaxy in the early universe, less than a billion years after the Big Bang. These galaxies are forming stars more than a hundred times faster than our own Milky Way. The discovery could explain an earlier finding: a population of surprisingly massive galaxies at a time 1.5 billion years after the Big Bang, which would require such hyper-productive precursors to grow their hundreds of billions of stars. The observations also show what appears to be the earliest image of galaxies merging. The results, by a group of astronomers led by Roberto Decarli of the Max Planck Institute for Astronomy, have been published in the 25 May issue of the journal Nature.