Dark matter from billions of years ago was finally discovered by scientists on Earth.
Researchers have been able to study the nature of the dark matter that surrounded galaxies as they appeared 12 billion years ago. That’s billions of years earlier than we’ve ever seen before.
Scientists hope the groundbreaking results could unveil the secrets of the still-mysterious dark matter that makes up a significant but largely unknown part of our universe.
There have already been tantalizing clues about the history of our cosmos. Researchers say the results suggest the basic rules of the universe were different in its earliest times.
As the name suggests, scientists cannot see dark matter directly because it does not emit light. Instead, scientists typically watch light travel through the galaxies they want to study and measure how it moves — 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 recognized and the dark matter cannot be analyzed.
As a result, scientists were unable to study dark matter from more than 10 billion years ago. The time before that and the beginning of the universe 13.7 billion years ago remained incomprehensible.
Now scientists say they have overcome this problem by using another source: the microwaves released by the Big Bang. The team measured how these microwaves were distorted, rather than light, allowing them to see dark matter from the early days of the cosmos and galaxies just 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 Institute for Cosmic Ray Research at the University of Tokyo. “However, we were able to 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 the clumping of dark matter in the early Universe. The theory says that the dark matter in the cosmos should stick together and form clumps – but there has been much less of it than predicted.
“Our outcome is still uncertain,” said Hironao Miyatake of Nagoya University, who led the team. “But if it’s true, going further back in time would suggest that the entire model is flawed. This is exciting because if the result holds after reducing the uncertainties, it could indicate an improvement in the model that could provide insight into the nature of dark matter itself.”
An article describing the results is published in Physical Verification Letters.