Cosmic Web of 'Dark Matter Bridges' Link Galaxies Across the Universe

A dark matter bridge as revealed through weak gravitational lensing. University of Waterloo

Renaissance man Leonardo da Vinci once remarked: "Realize that everything connects to everything else." Now scientists are beginning to prove just how widely applicable this profound claim truly is.

Researchers at the University of Waterloo in Canada have used a technique called weak gravitational lensing to capture the first visual representation of dark matter — that theoretical, seemingly invisible stuff that might make up as much as 84 percent of the universe. The image reveals what appears to be a "dark matter bridge" connecting two distant galaxies, a finding that could corroborate theories that imagine dark matter as a sort of cosmic web linking together galaxies across the universe, reports Wired.

Gravitational lensing is an effect that causes the images of distant galaxies to warp slightly under the influence of some large mass. For instance, astronomers can become cued to the presence of black holes because of their strong lensing effect. The question that University of Waterloo researchers wondered was: Could the same technique be used to reveal the presence of dark matter bridges?

It turns out, the answer is yes. The team constructed a composite image of more than 23,000 galaxy pairs that were spotted 4.5 billion light-years away. The dark matter bridges were most apparent between systems less than 40 million light-years apart.

"For decades, researchers have been predicting the existence of dark matter filaments between galaxies that act like a web-like superstructure connecting galaxies together," explained Mike Hudson, a professor of astronomy at the University of Waterloo, in the journal Monthly Notices of the Royal Astronomical Society. "This image moves us beyond predictions to something we can see and measure."

The existence of dark matter was first proposed to explain the rapid rotation rates of galaxies. If galaxies were only built from visible matter, then their gravitational force wouldn't be strong enough to hold them together while spinning so fast. So, theorists proposed, there must exist large quantities of invisible matter to compensate for the gravitational deficit of the visible matter.

From this, astrophysicists have imagined a universe teeming with fine threads of this mysterious dark stuff, threads that may act as a sort of "cosmic scaffolding" that coordinate some of the large-scale movements of the heavens.

To actually be able to "see" some of these dark matter bridges is profound indeed. The technique could be refined to more accurately map the distribution of dark matter throughout the universe, and perhaps eventually reveal clues about its mysterious design.