ESA's Herschel infrared space observatory has discovered that galaxies do not need to collide with each other to drive vigorous star birth. The finding overturns this long-held assumption and paints a more stately picture of how galaxies evolve. The observations realised by ESA's space telescope Herschel show that the collisions between galaxies only have a secondary role in the star birth process. At the time when the stars were born, the quantities of gas involved in the galaxies were enough to "spontaneously" generate a heavy production of stars. These results, obtained in the GOODS-Herschel international programme framework, which join, on the French side, researchers from CEA, CNRS, and Pierre and Marie Curie, Paris Diderot, Paris Sud and Provence universities, supported by CNES, describe the scenario of the evolution of galaxies less tormented than was thought by scientists. These results are published online on September 13, 2011, by Astronomy and Astrophysics.