Highly energetic and difficult to detect, neutrinos travel billions of light years before reaching our planet. Although it is known that these elementary particles come from the depths of our universe, their precise origin is still unknown. An international research team, led by the University of Würzburg and the University of Geneva (UNIGE), is shedding light on one aspect of this mystery: neutrinos are thought to be born in blazars, galactic nuclei fed by supermassive black holes. These results are published in the journal The Astrophysical Journal Letters.