Sep 8, 2020 - Science

The hunt for dark matter expands

a telescope in space

Illustration: Aïda Amer/Axios

The hunt for dark matter — the mysterious substance that makes up the majority of matter in the universe but hasn't been directly observed — is turning to new places and looking for new candidates.

The big picture: Regular matter — the stuff that makes up you, me and everything we know and see out in the universe — is only 15% of the total matter in the universe.

  • About 83% is dark matter, but scientists still don't understand its properties, nor have they detected it directly, though they see evidence of it in the way galaxies are structured and cluster.

What's happening: Much of the direct hunt for dark matter today takes place in high-powered, underground detectors designed to sniff out WIMPs — weakly interacting massive particles — that are the most likely dark matter candidates.

  • New studies, however, suggest there might be other ways of probing the nature of dark matter to figure out what it is, whether that's WIMPs or something else entirely.
  • By creating a simulated universe, the authors of a study published in the journal Nature last week were able to reveal what could be clumps of dark matter that may surround galaxies, suggesting that future experiments might be able to unveil that dark matter using powerful telescopes.
  • Some scientists are now advocating for new, powerful tools in space and on Earth to continue hunting for dark matter by looking in different places.

The state of play: "There's just this huge variety of dark matter models that are being talked about now that weren't talked about all that much while everybody was trying to find WIMPs with underground detectors," cosmologist Katie Mack told me.

  • Some of those models include the possibility that primordial black holes — the first black holes to form after the Big Bang — could actually be a form of dark matter while others suggest that different particles, like axions, could be dark matter.
  • The LISA telescope, expected to launch in the 2030s, could also hunt for a dark matter signal in a brand new way: through gravitational waves, the ripples in space and time sent out by colliding black holes.

Yes, but: It takes time and significant money to bring new detectors online, and funding agencies may not be willing to invest in a project without the field's overwhelming support.

  • "You have to go into this investigation — from designing and planning and then building stuff — by first assuming what you think the dark matter is," Sownak Bose, one of the authors of the Nature study, told me.

What's next: It's still possible the current generation of detectors could find dark matter in the coming years. But time is running out for them.

  • At some point in the next decade, direct detectors will hit what's known as the "neutrino floor," where observations will be obscured by neutrinos streaming from space.
  • After that, underground detectors won't be able to meaningfully continue the hunt, making it necessary to look for dark matter in other ways if it hasn't been identified yet.
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