Disturbing evidence has emerged from the wreckage of an intergalactic pile-up suggesting that the already mysterious substance known as dark matter may be even less well understood than astronomers thought.

The observations come from a massive galaxy cluster called Abell 520 that lies 3 billion light years away. Abell 520 turns out to hold a massive dark core, empty of bright galaxies.

The observation may rule out the standard model of cosmology, called lambda-CDM, which assumes that dark matter only interacts very weakly.