Stars flung from their home galaxies could shed light, help us “see” dark matter

The technique gives astronomers the most accurate measurements of dark matter made so far.


The quest to "see" dark matter in the universe has been a long one that still isn't near over.

This invisible force that supposedly makes up 85 percent of the universe also has its role to play in the force of gravity that keeps all the galaxies in the universe from spinning into the abyss (and ramming into each other).

Despite its abundance, everything we know about dark matter comes from indirect measurements of other forms of energy. Instruments that have helped shape what we know about dark matter are pricey and require experts that can grapple with hardcore physics and mathematics to decode.

Scientists have now suggested that there could be a much simpler and easier way to find this elusive, omnipresent force in the universe.

Stars flung from their home galaxies could shed light, help us “see” dark matter

Abell S1063, a galaxy cluster, was observed by the NASA/ESA Hubble Space Telescope as part of the Frontier Fields programme. The huge mass of the cluster — containing both baryonic matter and dark matter — acts as cosmic magnification glass and deforms objects behind it. In the past astronomers used this gravitational lensing effect to calculate the distribution of dark matter in galaxy clusters. A more accurate and faster way, however, is to study the intracluster light (visible in blue), which follows the distribution of dark matter. Image: ESA

The technique uses light emitted by stars that are torn away from their parent galaxies, which NASA scientists think could give far more accurate readings of dark matter than were possible so far.

In a study pre-published in ArXiv, NASA astronomers describe how these measurements can be made: by recording 'intracluster light' given off by these stars that have been ripped away from their galactic homes.

The study also features images captured by the Hubble telescope of intracluster light from these flung stars. The intensity of this emitted light seems to neatly tie into the amount of dark matter recorded from indirect measurements.

Instead of orbiting near the core of their galaxies, these stars move through the universe more chaotically, carrying some amount of dark matter with them, the study suggests.

This image of the Milky Way in visible light with a superimposed gamma-ray map of the galactic center was released by NASA in Feb, 2017 from Fermi telescope data. With all known sources removed, the map shows a gamma-ray excess, hinting that it could be a cloud of dark matter. Image courtesy: NASA

This image of the Milky Way in visible light with a superimposed gamma-ray map of the galactic center was released by NASA in Feb, 2017 from Fermi telescope data. With all known sources removed, the map shows a gamma-ray excess, hinting that it could be a cloud of dark matter. Image courtesy: NASA

Pointing and reading intensity measurements from single stars in a vacuum is far easier than a wild goose-chase for dark matter tied up in a galaxy's core.

“We have found a way to ‘see’ dark matter,” Mireia Montes, lead author of the study from the University of New South Wales said in a statement. “We have found that very faint light in galaxy clusters, the intracluster light, maps how dark matter is distributed.”

This could also one day open up research to look at the dark matter that is at the core of galaxies, which could change a lot of fundamental concepts researchers know about the universe today.

Ignacio Trujillo, co-author of the study said, “There are exciting possibilities that we should be able to probe in the upcoming years by studying hundreds of galaxy clusters.”