Dark matter from billions of years ago has finally been discovered by scientists on Earth.
Researchers have been able to probe the nature of the dark matter that surrounded galaxies as they were 12 billion years ago. That’s billions of years earlier than we’ve ever been able to see.
Scientists hope the breakthrough discoveries could unlock the secrets of the still-mysterious dark matter, which makes up a significant portion of our universe but is largely unknown.
It has already offered tantalizing clues about the history of our cosmos. Researchers say the findings suggest that the fundamental rules of the universe were different in its earliest times.
As its name suggests, scientists cannot see dark matter directly because it does not emit light. Instead, scientists typically watch how light travels through the galaxies they want to study, measuring how it travels—the more it’s distorted, the more dark matter there is.
However, the most distant galaxies – which we see as they existed billions of years ago – are too faint for this technique to work. The distortion cannot be properly detected and dark matter remains impossible to analyze.
This has left scientists unable to study dark matter from more than about 10 billion years ago. The time before that, and the beginning of the universe, 13.7 billion years ago, remains incomprehensible.
Now scientists say they have overcome this problem by using a different source: the microwaves that were released from the Big Bang. The team measured how these microwaves were distorted, not light, and thus were able to see dark matter from the 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’s Cosmic Ray Research Institute. “However, we can look further back in time because we used the more distant CMB to measure dark matter. For the first time, we have measured dark matter from almost the earliest moments of the universe.
The results revealed a number of surprises, including showing how dark matter accumulated in the early universe. Theory suggests that dark matter should clump together and form clumps in space – but this is much less than predicted.
“Our finding is still uncertain,” said Hironao Miyatake of Nagoya University, who led the team. “But if it’s true, it would mean that the whole model is wrong when you go further back in time. This is exciting because if the result holds after reducing the uncertainty, it could offer an improvement to the model that could provide insight into the nature of dark matter itself.
A paper describing the findings has been published in Physical Review Letters.
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