Astronomers measure dark matter from the ‘first moments of the universe’

Twisted in our universe lies one of science’s greatest unsolved mysteries. Where is all the dark matter? What is all dark matter?

I mean, we know it’s there.

Galaxies, including the Milky Way, spin so rapidly that our physics predict that everything inside should be thrown outward like horses on an unbalanced merry-go-round. But obviously it doesn’t work. You, me, the sun and the earth are securely anchored. Therefore, scientists hypothesize that something – probably in the form of a halo – must surround the galaxies to keep them from collapsing.

Anything that includes these boundaries is called dark matter. We can’t see it, we can’t feel it, and we don’t even know if it’s a thing. It is the quintessence of the elusive. We only know that dark matter exists.

Despite our inability to see or touch the material itself, experts have some interesting ways to identify the effects it has on our universe. After all, we deduced the presence of dark matter in the first place by noticing how it holds galaxies together.

Scientists have taken advantage of this principle, announcing remarkable new discoveries about dark matter on Monday. With a toolkit of warped space, cosmic remnants left over from the Big Bang, and powerful astronomy instruments, they detected a deep space area of ​​previously unstudied dark matter halos – each located around an ancient galaxy, dutifully protecting it from a joyous life. -round nightmare.

These vortices, according to a study on the discovery published in Physical Review Letterstraced back 12 billion years, a little less than two billion years after the Big Bang. This could very well make them the youngest rings of dark matter ever studied by mankind, the authors suggest, and potentially the prelude to the next chapter in cosmology.

“I was happy that we opened a new window on this era,” said Hironao Miyatake of Nagoya University and author of the study, said in a press release. “Twelve billion years ago things were very different. You see more galaxies being formed than today; the first clusters of galaxies are also beginning to form.”

Wait, warped space? Cosmic residue?

Yes, you read that right. Let’s explain.

Over a century ago, when Albert Einstein invented his famous theory of general relativity, one prediction he made was that super strong gravitational fields from massive amounts of matter would literally warp the fabric of the space and time, or space-time. He turned out to be right. Today, physicists are exploiting the concept by using a technique called gravitational lensing to study very distant galaxies and other phenomena in the universe. It works something like this.

Imagine two galaxies. Galaxy A is in the background and B is in the foreground.

Basically, when light from galaxy A passes through galaxy B to reach your eyes, that luminescence is distorted by matter from B, dark or otherwise. This is good news for scientists, because such distortion often magnifies distant galaxies, a bit like a lens.

Also, there’s a kind of reverse calculation you can do with this light distortion to figure out how much dark matter surrounds galaxy B. If galaxy B contained a plot of dark matter, you would see a plot more distortion than expected of visible matter – what we can see – inside. But if there weren’t so much dark matter, the distortion would be much closer to your prediction. This system has worked quite well, but it comes with a caveat.

This sketch shows light paths from a distant quasar, which is a very bright object at the center of a galaxy, being gravitationally lensed by a foreground galaxy on its way to the Hubble Space Telescope lens.

NASA, ESA and D. Player (STScI)

The standard gravitational lens only allows researchers to identify dark matter around galaxies between 8 and 10 billion light-years away, at most.

Indeed, as you look deeper and deeper into the universe, visible light becomes harder and harder to interpret, eventually even turning into infrared light that is completely invisible to the human eye. (That is why NASA’s James Webb Space Telescope is so important. This is our best chance of catching the faintest, most invisible light from the distant cosmos.) But that means visible light distortion signals for dark matter studies become far too faint beyond from a certain point to help us analyze the hidden elements.

Miyatake found a workaround.

Maybe we can’t notice the standard light distortions for detecting dark matter, but what if there’s another kind of distortion we can see? It turns out there is: the microwave radiation emitted by the Big Bang. This is roughly remnant heat from the Big Bang, officially known as Cosmic Microwave Background Radiation, or CMB, radiation.

“Look at dark matter around distant galaxies?” Masami Ouchi, a cosmologist at the University of Tokyo and co-author of the study, said in a statement. “It was a crazy idea. Nobody realized that we could do that. But after giving a lecture on a large sample of distant galaxies, Hironao came to me and said that it might be possible to observe dark matter around these galaxies with the CMB. ”

Essentially, Miyatake wanted to observe how dark matter gravitationally crystallized the first light in our universe.

Picking up pieces of the Big Bang

“Most researchers use source galaxies to measure the distribution of dark matter from the present to 8 billion years ago,” said Yuichi Harikane, assistant professor at the University of Tokyo and co-author of the study, in a press release. “However, we could look further into the past because we were using 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.”

To arrive at their results, the new study team first gathered data from observations taken by the Subaru Hyper Suprime-Cam survey.

This led them to identify 1.5 million lens galaxies – a group of hypothetical B galaxies – that could be 12 billion years old. They then called on information from the Planck satellite of the European Space Agency on the microwave radiation of the Big Bang. Put it all together and the team could find out if and how these lensed galaxies were distorting microwaves.

A view of hundreds (maybe thousands) of galaxies in deep space

The first deep field of the James Webb Space Telescope was revealed on July 11. You can see a ton of gravitational lensing there, as indicated by the galaxies stretching towards the center.


“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 Neta Bahcall, professor of astrophysical sciences at the University. of Princeton and co-author of the study. , said in a statement.

Notably, the researchers highlighted their study by finding that dark matter from the early universe does not appear to be as clumped together as our current physical models suggest. Ultimately, this bit could adjust what we currently believe about cosmology, mostly theorems rooted in what’s called the Lambda-CDM model.

“Our discovery is still uncertain,” Miyatake said. “But if true, that would suggest that the whole model is flawed as you go back in time. This is exciting because if the result holds after reducing uncertainties, it could suggest an improvement in the model that could provide insight. in the nature of dark matter itself.”

And then the study team wants to explore even older regions of space by tapping into information held by the Vera C. Rubin Observatory’s Legacy Survey of Space and Time.

“LSST will allow us to observe half the sky,” Harikane said. “I see no reason why we couldn’t see the distribution of dark matter 13 billion years ago.”

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