For the first time, astronomers say they spotted a string of dark matter via gravitational lensing.
A giant string of invisible dark matter has been discovered across the universe between a pair of galaxy clusters.
The filament forms a bridge between two huge clusters called Abell 222 and Abell 223, which lie 2.7 billion light-years away. The universe is thought to be filled with such strings of dark matter, a mysterious substance that cannot be seen, only sensed through its gravitational pull.
Scientists have made previous attempts to find dark matter filaments, which are predicted by theories that suggest galaxy clusters form at the intersections of filaments. Dark matter is thought to make up 83 percent of all matter in the universe.
"This is the first time [a dark matter filament] has been convincingly detected from its gravitational lensing effect," said astronomer Jörg Dietrich of the University Observatory Munich, in Germany. "It's a resounding confirmation of the standard theory of structure formation of the universe. And it's a confirmation people didn't think was possible at this point."
Many astronomers thought detecting filaments would have to wait until telescopes became significantly more advanced, but Dietrich and his colleagues benefited from the rare spatial geometry of this cluster, which allowed them to detect signs of what's called weak gravitational lensing. [Gallery: Dark Matter Throughout the Universe]