Image confirms galaxies are connected by dark matter web

A survey of weak gravitational lensing among the light from galactic pairs revealed filaments of dark matter stringing together galaxies -- a dark matter web. Photo by S. Epps & M. Hudson/University of Waterloo

April 12 (UPI) — A new composite image captured by researchers at the University of Waterloo in Ontario, Canada, offers proof galaxies are connected by a web of dark matter.

The universe’s cosmic web of dark matter has remained elusive, but Waterloo researchers were able to tease out its existence by tracing a weak gravitational lensing.

Typically, astronomers used gravitational lensing events to study the light from distant galaxies as the beams are warped by massive galactic structures. But the gravity of smaller cosmic objects can bend light, too — including strands of dark matter.

Researchers surveyed 23,000 galaxy pairs located 4.5 billion light-years away using observations from the Canada-France-Hawaii Telescope. Scientists teased out subtle warping among the galactic light. A composite image of the galactic pairs revealed the weak gravitational lensing and the presence of dark matter filaments between the galaxies.

“For decades, researchers have been predicting the existence of dark-matter filaments between galaxies that act like a web-like superstructure connecting galaxies together,” Mike Hudson, a professor of astronomy at Waterloo, said in a news release. “This image moves us beyond predictions to something we can see and measure.”

Hudson and his colleagues detailed their efforts in the journal Monthly Notices of the Royal Astronomical Society.

“By using this technique, we’re not only able to see that these dark matter filaments in the universe exist, we’re able to see the extent to which these filaments connect galaxies together,” said co-author and Waterloo grad student Seth Epps.


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