Black hole jets on the scale of the Cosmic Web

Jets launched by supermassive black holes transport relativistic leptons, atomic nuclei, magnetic fields, and heat from the centres of galaxies to their outskirts and beyond. These outflows embody the most energetic pathway by which galaxies respond to the Cosmic Web around them. Understanding black hole feedback is an astrophysical frontier, given its consequences for the cosmic star formation history, the stability of galaxy clusters, and the origin of cosmic rays, heavy elements, and magnetism throughout the Universe. The importance of this feedback to cosmology is ultimately bounded by the reach of black hole jets, and could be sweeping if jets travel far at early epochs. Here we present the joint LOFAR–uGMRT–Keck discovery of a black hole jet pair extending over 7 megaparsecs — the largest galaxy-made structure ever found. The outflow, seen 7.5 gigayears into the past, spans two-thirds of a typical cosmic void radius, thus penetrating voids at high (∼95%) probability. This system demonstrates that black hole–launched jets can avoid destruction by magnetohydrodynamical instabilities over cosmological distances, even at epochs when the Universe was 15–7 times denser than it is today. Whereas previous record-breaking outflows were powered by radiatively inefficient active galactic nuclei, the current outflow is powered by a radiatively efficient active galactic nucleus, a type more common at early epochs. If, as implied, a population of early void-penetrating outflows existed, then black hole jets could have overwritten the fields from primordial magnetogenesis. This outflow shows that energy transport from supermassive black holes operates on scales of the Cosmic Web and raises the possibility that cosmic rays, heavy elements, and magnetism in the intergalactic medium have a non-local, cross-void origin.