Although dark matter exists only in theory, scientists strongly believe that it is an all-pervasive reality in galaxy clusters, accounting for 85 percent of all matter in the known and unknown universe.
Their conviction is based on astrophysical observations such as unexplained gravitational forces, which, obviously, can’t come from nothing.
Meaning, while they can see the powerful gravitational effects of the so-called dark matter, they can’t really see the matter itself; hence, the name.
Well, they now have a reason to rejoice as a new study claims to have found a way to track the dark matter.
Using deep-space imagery captured by the Hubble Telescope, astronomers Mireia Montes (School of Physics, University of New South Wales, Australia) and Ignacio Trujillo (Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain) were able to see the invisible matter in an unprecedented light, literally.
This is a press release from our latest work where we find that the diffuse light in clusters of galaxies is a good tracer of how dark matter distributes in those clusters. Check it! https://t.co/GTf6MwIbBB
— Mireia Montes (@mireiamontesq) December 23, 2018
The powerful data from the Hubble Frontier Fields program of the NASA/ESA-owned telescope enabled Montes and Trujillo to demonstrate that the faint light emitted by abandoned stars in galaxy clusters, known as intracluster light (ICL), actually follow the distribution of dark matter within them.
“We have found a way to ‘see’ dark matter,” said Montes, who’s the lead author of the joint study published online in the MONTHLY NOTICES of the Royal Astronomical Society.
“We have found that very faint light in galaxy clusters, the intracluster light, maps how dark matter is distributed,” she added.
Could the faint glow between the members of massive galaxy clusters be a clue to the nature of dark matter? A new study explores the tantalizing possibilities: https://t.co/mCqP0JXotJ #Hubble #HubbleScience #NASA #DarkMatter pic.twitter.com/2F0pltrqQE
— HubbleTelescope (@HubbleTelescope) December 20, 2018
Experts believe that this new dark matter-hunting technique will lead the way to more discoveries about this mysterious phenomenon that permeates almost all of the universe.
“There are exciting possibilities that we should be able to probe in the upcoming years by studying hundreds of galaxy clusters,” says study co-author Ignacio Trujillo.
A galaxy cluster is a collection of galaxies bound together by each other’s powerful gravitational forces.
Our own Milky Way is part of a ‘Local Group’ of 54 galaxies spanning 10 million lightyears, which in turn is part of a much larger group of hundreds of thousands of galaxies known as the Laniakea Supercluster spanning 500 million lightyears.
Due to the strong galactic influences at play in a cluster, stars are sometimes torn away from their home galaxy and drift aimlessly through the cluster.
These galactic orphans emit the faint intracluster light, or ICL, discussed earlier, which aligns with the gravitational forces of the invisible dark matter, which is how Montes and Trujillo were able to locate its position.
“The reason that intracluster light is such an excellent tracer of dark matter in a galaxy cluster is that both the dark matter and these stars forming the intracluster light are free-floating on the gravitational potential of the cluster itself—so they are following exactly the same gravity,” says Montes.
“We have found a new way to see the location where the dark matter should be, because you are tracing exactly the same gravitational potential,” she said, adding, “We can illuminate, with a very faint glow, the position of dark matter.”
In the past, astronomers have used “gravitational lensing models” to follow the distribution of dark matter within clusters, which, for all practical purposes, is a complex time-consuming method.
Montes and Trujillo compared the distribution of ICL they discovered with previous dark matter maps created through the gravitational lensing method and found that both distribution patterns were identical.
“These stars have an identical distribution to the dark matter, as far as our current technology allows us to study,” Montes said.
The Montes-Trujillo way of doing things is simpler, more efficient and faster because all that is needed is deep-space imagery.
This new method will now make it possible for astronomers to study many more clusters in the shortest possible time.
“This method puts us in the position to characterize, in a statistical way, the ultimate nature of dark matter,” Montes said.
“The idea for the study was sparked while looking at the pristine Hubble Frontier Field images,” said Trujillo.
“The Hubble Frontier Fields showed intracluster light in unprecedented clarity,” he said adding that “the images were inspiring.”
“Still, I did not expect the results to be so precise. The implications for future space-based research are very exciting,” he added.