Astronomers have taken their first 3D look at a gigantic filament of dark matter, an invisible cosmic structure that can only be detected by its gravitational effects it has on its surroundings.

The universe is thought to be structured like a tangled web, with long strings of mostly dark matter intersecting at giant galaxy clusters. Since dark matter cannot be seen directly, these filaments are difficult to observe. But using the Hubble Space Telescope, astronomers have managed to probe one of the elusive cosmic strands in 3D. The researchers sought out a 60 million light-year strand of dark matter around the massive galaxy cluster MACS J0717. The galaxy cluster is one of the largest yet seen and is about 5.4 billion light-years from Earth.