Astronomers detect dark matter from the ‘early moments of the universe’


Our universe hides one of science’s greatest unsolved mysteries: dark matter. We know it exists because it is thanks to it that the galaxy and our Milky Way can spin so fast without dispersing. But we cannot see or feel it. Dark matter is elusive.

Nevertheless, scientists have ways to detect its effects on our universe. They just announced an amazing new invention. Using a toolbox of warped spacetime, cosmic remnants left over from the Big Bang, and powerful astronomical instruments, they detected a previously unseen region of dark matter in deep space. studied, located around an ancient galaxy.

Research published on this discovery
Physical review letter, these eddies date back 12 billion years, just two billion years after the Big Bang. The scientists behind the discovery believe they may be the earliest elements of dark matter studied by mankind and could be a possible precursor to the next chapter in the cosmos.


I’m glad we opened a new window on that era
Hironao Miyatake of Nagoya University and the author of the study. ”
12 billion years ago, things were very different. More galaxies are being formed than you are now; The first clusters of galaxies also began to form.
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Distorted space-time, cosmic remnants. What is it about?

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

Here’s 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 eye, this light is distorted by matter from B. This is an advantage for scientists, as this distortion often magnifies distant galaxies, like a magnifying glass.

This drawing depicts the light paths from a distant quasar, a very bright object at the center of a galaxy, that the telescope lens Hubble experiences gravitational lensing from a galaxy in the foreground on its way into space. NASA, ESA and D. Player (STScI)

Moreover, it is possible to do an inverse calculation with this distortion of light to estimate the amount of dark matter around the B galaxy. If the latter contains a large amount of dark matter, the distortion will be much greater than expected from within visible matter. A galaxy, on the other hand, if it doesn’t have as much dark matter, then the distortion will be much closer to your prediction. This system has worked quite well, but there is a downside.

Standard gravitational lensing only allows researchers to detect 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 transforms into infrared light, which is completely invisible to the human eye. This means that visible light distortion signals become too weak beyond a certain point to help us analyze hidden objects for studying dark matter. This is why the James-Webb Space Telescope is so important because it represents our best chance to capture the faintest and most invisible light from the distant cosmos.

Professor Miyatake found a solution to overcome this limitation. If we don’t see the distortion of light ideal for detecting dark matter, then maybe we see some other kind of distortion? Turns out there is one: microwave radiation emitted by the Big Bang. It’s actually the leftover heat from the Big Bang, formally known as the Cosmic Microwave Background or CMB (Cosmic microwave background)

Remnants of the Big Bang


Most researchers use source galaxies to measure the distribution of dark matter 8 billion years before the present
said Yuichi Harikane, assistant professor at the University of Tokyo and co-author of the study. ”
However, we were able to make more observations in the past because we used the more distant CMB to measure dark matter. For the first time, we are measuring dark matter from almost the earliest moments of the universe.
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To reach these results, the new team identified 1.5 million gravitational lensing galaxies, a group of hypothetical B galaxies, that originated 12 billion years ago. They then used data from the European Space Agency’s Planck satellite on microwave radiation from the Big Bang. By combining all these elements, astronomers were able to determine whether these galaxies distorted the microwaves.


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

The researchers concluded in particular that the dark matter from the early universe does not appear to be as dense as our current physical models suggest. Ultimately, this discovery could change our beliefs in cosmology, primarily based on the lambda-CDM model.

Our findings are still uncertain Recognizes Professor Miyat. ”
But if true, it suggests that the whole model is flawed because a time goes back This is exciting because if the result holds after reducing the uncertainty, it could suggest an improvement in the model that could provide insight into the nature of dark matter.
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Moving forward, the study team Vera C. Rubin intends to use data from the Observatory’s Space and Time Legacy Survey to explore even older regions of space. ” LSST will allow us to observe half the sky Yuichi added to the hurricane. ”
I don’t see why we couldn’t observe the distribution of dark matter 13 billion years ago.”

CNET.com article adapted by CNETFrance

Photo: Reiko Matsushita

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