- Physicists detected dark matter from 12 billion years ago in a new study.
- They used a technique called gravitational lensing to probe the distribution of dark matter around ancient galaxies.
- Dark matter is a mysterious, invisible substance that makes up the majority of all matter in the universe.
Scientists have now glimpsed the distribution of dark matter around galaxies 12 billion years ago, marking the earliest detection of the mysterious substance yet.
In a new study, published Monday in the journal Physical Review Letters, scientists spotted dark matter — a mysterious, invisible substance that makes up the majority of all matter in the universe — dating back 12 billion years, just under two billion years after the Big Bang.
"For the first time, we were measuring dark matter from almost the earliest moments of the universe," Yuichi Harikane, study co-author and assistant professor at the University of Tokyo, said in a press release. He added, "12 billion years ago, things were very different. You see more galaxies that are in the process of formation than at the present; the first galaxy clusters are starting to form as well."
Though dark matter makes up about 27% of the universe, astronomers cannot directly detect it, in part because it does not emit light. But researchers can observe the gravitational effect dark matter has on visible matter, like galaxies, warping light to act like a lens on distant objects behind them.
In the study, researchers used the same technique — called gravitational lensing — to measure distortions from the very first light in the universe. The cosmic microwave background, or CMB, is radiation left over from the Big Bang, which is distributed throughout the entire cosmos. Researchers selected selected 1.5 million galaxies — all seen as they were about 12 billion years ago — to collectively serve as the gravitational lens. They analyzed distortions from this ancient residual light, allowing researchers to reconstruct the distribution of dark matter in these lens galaxies.
Researchers found that dark matter from the early universe doesn't seem to be as clumpy as present physics models suggest.
"Our finding is still uncertain," Hironao Miyatake, co-author of the study, and a cosmologist at Nagoya University, said in a press release. "But if it is true, it would suggest that the entire model is flawed as you go further back in time."
"This is exciting because if the result holds after the uncertainties are reduced, it could suggest an improvement of the model that may provide insight into the nature of dark matter itself," Miyatake added.