See the first image of dark matter web stretching across galaxies

12 Apr 2017

Abstract image of dark matter in the universe. Image: Oleg1969/Shutterstock

For decades, astrophysicists have tried to find evidence of a cosmic web of dark matter stretching across galaxies – now they have found it.

Dark matter remains a controversial subject within the astrophysics community, with suggestions that the elusive material – completely different from anything we know – makes up at least 25pc of the universe.

Yet in some academic circles, it is believed to not exist at all, and the reason we have not been able to prove it is that, supposedly, it is a variation of gravity itself.

Like a thick, dark matter web

Now, researchers from the University of Waterloo (UW) have released a composite image that appears to show proof of the existence of dark matter, stretching like a spider’s web between two neighbouring galaxies.

In a paper published to the Monthly Notices of the Royal Astronomical Society, the researchers tried to prove its existence using a technique called weak gravitational lensing.

This process causes the images of distant galaxies to warp slightly under the influence of an unseen mass such as a planet, a black hole or, in this case, dark matter.

By combining lensing images from more than 23,000 galaxy pairs located 4.5bn light years away, the team then created a composite image – similar to a map – that visually represents the presence of dark matter between each of the galaxy pairs.

It was also noted that the dark matter bridge is at its strongest between systems less than 40m light years apart.

Dark matter image

Dark matter filaments bridge the space between galaxies in this false colour map. Image: S Epps and M Hudson/University of Waterloo

No longer just predictions

“For decades, researchers have been predicting the existence of dark-matter filaments between galaxies that act like a web-like superstructure connecting galaxies together,” said Mike Hudson, professor of astronomy at UW.

“This image moves us beyond predictions to something we can see and measure.”

Last February, a team of international researchers announced the discovery of a number of peculiar signals being emitted by our own neighbouring galaxy, Andromeda.

Using NASA’s Fermi Gamma-ray Space Telescope, the team discovered that, unlike a typical galaxy, gamma rays in Andromeda are confined within its bright centre rather than spread throughout.

This, the astronomers suggested, could indicate that the gamma-ray emission comes from several undetermined sources, and one of them might be dark matter.

Colm Gorey was a senior journalist with Silicon Republic