Astronomers back in the dark over dark matter after new findings by Durham University team
Scientists are back in the dark over what dark matter could be, after new observations cast doubt on a previous breakthrough.
Researchers thought they were one step closer to identifying the mysterious substance when they noticed a galaxy in a cluster had become separated from the dark matter surrounding it three years ago.
The discovery, by astronomers led by Durham University, suggested the substance was interacting with other dark matter through forces other than gravity.
However data from more recent observations has revealed the location of otherwise invisible dark matter, showing it did not separate from its galaxy after all.
Around 27% of the universe is dark matter, which cannot be seen, while normal matter such as planets and stars makes up about 5%.
Relatively little is known about the substance but scientists say galaxies like the Milky Way exist inside clumps of dark matter and would be unable to stay intact without the effect of its extra gravity.
Lead author Dr Richard Massey, from Durham University's Centre for Extragalactic Astronomy, said: "The search for dark matter is frustrating, but that's science.
"Meanwhile the hunt goes on for dark matter to reveal its nature.
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"So long as dark matter doesn't interact with the universe around it, we are having a hard time working out what it is."
The apparent breakthrough was announced in 2015 following observations of a galaxy in the Abell 3827 cluster, approximately 1.3 billion light years from Earth, using the Hubble Space Telescope.
Until this point, dark matter had only been shown to interact with gravity.
The latest observations of the cluster were made using the Atacama Large Millimetre Array (ALMA) in Chile, South America.
ALMA picked up distorted infrared light from an unrelated background galaxy, which provided a higher resolution view and revealed the location of dark matter unidentified in the earlier study.
While the results show the dark matter stayed with its galaxy, the researchers said it did not necessarily mean the substance does not interact with forces other than gravity.
Dark matter could be interacting very little or this particular galaxy might be moving towards us, meaning we would not expect to see the substance displaced sideways, the team said.
The research will be presented at the European Week of Astronomy and Space Science meeting in Liverpool on Friday and published in the journal Monthly Notices of the Royal Astronomical Society.