As much as 30% of the Universe's observable matter could be hiding in enormous cosmic voids, where it is too sparse for scientists to observe.

Matter in the nearby Universe is said to be missing because astronomers have failed to see as much material as observations of the early Universe suggest there should be. To map how matter might be distributed, Markus Haider at the University of Innsbruck in Austria and his team used a simulation for how galaxies and intergalactic filaments evolved. This modelled the behaviour of both normal and dark matter — an invisible substance detected only by its gravitational pull — in a cube of space 350 million light years (about 107 million parsecs) across.

Analysis of the model, known as Illustris, suggests that the energy of radiating supermassive black holes has flung as much as 24% of normal matter out of galaxies and into voids, where an extra 6% that has yet to gather in filaments also lies. This could help to explain some of the missing matter, say the authors.

Mon. Not. R. Astron. Soc. 457, 3024–3035 (2016)