dark matter from billions of years ago has finally been detected by scientists on Earth.
The researchers were able to investigate the nature of the dark matter surrounding galaxies as they were 12 billion years ago. That’s billions of years earlier than we’ve ever seen before.
Scientists hope the groundbreaking findings could unlock the secrets of the still-mysterious dark matter that makes up a significant part of our universe, but is largely unknown.
It has already offered tantalizing clues about the history of our cosmos. The researchers say the findings suggest that the fundamental rules of the universe were different in its earliest days.
As its name suggests, scientists can’t see dark matter directly, because it doesn’t emit light. Instead, scientists typically watch how light travels through the galaxies they want to investigate, measuring how it travels: the more it distorts, the more dark matter there is.
However, the most distant galaxies, which we see as existing billions of years ago, are too faint for this technique to work. The distortion cannot be detected correctly, and the dark matter remains impossible to analyze.
That left scientists unable to probe dark matter for more than 10 billion years. The time before that and the beginning of the universe, 13.7 billion years ago, was still impossible to understand.
Now scientists say they have overcome that problem by using a different source: microwaves that were released by the Big Bang. The team measured how those microwaves, rather than light, were distorted, and in doing so were able to see dark matter from the very beginning of the cosmos, looking at galaxies soon after they formed.
“Most researchers use source galaxies to measure the distribution of dark matter from the present to eight billion years ago,” added Assistant Professor Yuichi Harikane of the University of Tokyo Cosmic Ray Research Institute. “However, we could look further back into the past because we use the more distant CMB to measure dark matter. For the first time, we were measuring dark matter from almost the earliest moments of the universe.”
The results showed a variety of surprises, including how dark matter accumulated in the early universe. Theory suggests dark matter should stick together and form clumps in the cosmos, but there was far less of it than expected.
“Our finding is still uncertain,” said Hironao Miyatake of Nagoya University, who led the team. “But if true, it would suggest that the whole model is flawed as you go back in time. This is exciting because if the perception result holds after uncertainties are reduced, it could suggest an improvement to the model that could provide insights into the nature of dark matter itself.”
An article describing the findings is published in Physical Review Letters.
