Astronomers discover dark matter from ‘early moments of universe’


Our universe holds one of science’s greatest unsolved mysteries: dark matter. We know it exists because it is thanks to it that the galaxies and our Milky Way can spin so fast without spreading. But we can neither see nor feel it. Dark matter is intangible.

Despite this, scientists have ways to identify the effects it has on our universe. They have just announced remarkable new discoveries. Using a toolbox of warped spacetime, cosmic remnants left over from the Big Bang, and powerful astronomical instruments, they discovered a previously unseen region of dark matter halos in deep space. studied, located around an ancient galaxy.

According to the study on this discovery published in
Physical review letters, these eddies date back 12 billion years, just under two billion years after the Big Bang. The researchers behind the discovery believe they may be the most primary elements of dark matter ever studied by humanity, and potentially the prelude to the next chapter in cosmology.


I was overjoyed that we opened a new window to that era
said Hironao Miyatake of Nagoya University and author of the study. ”
12 billion years ago, things were very different. You see more galaxies forming than currently; the first clusters of galaxies also begin to form.
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Distorted space-time, cosmic remnant. What is it about ?

Over a century ago, when Albert Einstein developed his general theory of relativity, he predicted that very strong gravitational fields from massive amounts of matter would literally distort the structure of space and time, or space-time. Turns out he was right. Today, physicists exploit this concept by using a technique called gravitational lensing to study very distant galaxies and other phenomena in the universe.

That is how it works. Imagine two galaxies. Galaxy A is in the background and Galaxy B is in the foreground.

Basically, when light from galaxy A passes through galaxy B to reach your eyes, this luminescence is distorted by matter from B. This is an advantage for scientists because this distortion often magnifies distant galaxies, like a magnifying glass.

This drawing illustrates the paths of light from a distant quasar, a very bright object at the center of a galaxy, experiencing gravitational lensing from a foreground galaxy en route to the Hubble Space Telescope lens. NASA, ESA and D. Player (STScI)

Moreover, it is possible to do a kind of reverse calculation with this distortion of light to determine the amount of dark matter surrounding galaxy B. If the latter contained a lot of dark matter, the distortion would be much greater than expected from visible matter inside the galaxy. On the other hand, if it did not contain so much dark matter, the distortion would be much closer to your prediction. This system worked quite well, but there is a downside.

Standard gravitational lensing only allows researchers to identify dark matter around galaxies at a maximum distance of 8 to 10 billion light years. In fact, as we go deeper into the universe, visible light becomes increasingly difficult to interpret and even ends up being transformed into infrared light, totally invisible to the human eye. This means that the visible light distortion signals for studying dark matter become far too weak beyond a certain point to help us analyze hidden matter. It is for this reason that the James-Webb Space Telescope is so important, because it represents our best chance of capturing the faintest and most invisible light from the distant cosmos.

Professor Miyatake has found a solution to circumvent this limitation. If we can’t see standard light distortions to detect dark matter, maybe there is another type of distortion we can see? It turns out there is one: the microwave radiation emitted by the Big Bang. It is actually remnants of the heat from the Big Bang, officially known as the Cosmic Microwave Background or CMB (cosmic microwave background).

The remnants of the Big Bang


Most researchers use source galaxies to measure the distribution of dark matter from the present to 8 billion years ago
says Yuichi Harikane, assistant professor at the University of Tokyo and co-author of the study. ”
However, we were able to observe further earlier because we used the more distant CMB to measure dark matter. For the first time, we have measured dark matter since almost the earliest moments of the universe.
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To arrive at these results, the new team identified 1.5 million gravitational lensing galaxies, a group of hypothetical B galaxies whose origins date back 12 billion years. They then used information from the European Space Agency’s Planck satellite about the microwave radiation from the Big Bang. By combining all these elements, astronomers were able to determine if and how these galaxies were distorting microwaves.


This result provides a very consistent picture of galaxies and how they evolve, as well as dark matter in and around galaxies and how the picture changes over time.
said Neta Bahcall, professor of astrophysical sciences at Princeton University and co-author of the study.

In particular, the researchers highlighted the conclusion of their study that dark matter from the earliest moments of the universe does not appear to be as dense as our current physical models suggest. Ultimately, this discovery may change our beliefs about cosmology, primarily theorems based on the Lambda-CDM model.

Our discovery is still uncertain recognizes Professor Miyatake. ”
But if true, it suggests that the whole model is flawed going back in time. This is exciting because if the result holds after reducing the uncertainty, it could indicate an improvement to the model that could provide insight into the nature of dark matter itself.
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Going forward, the research team wants to explore even older regions of space by exploiting information contained in the Vera C. Rubin Observatory’s Legacy Survey of Space and Time. ” LSST allows us to observe half the sky adds Yuichi Harikane. ”
I don’t see why we couldn’t observe the distribution of dark matter 13 billion years ago.”

CNET.com article adapted by CNETFrance

Image: Reiko Matsushita

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