Dark matter from 12 billion years ago detected for the 1st time

Informed 6 days ago (Wed, Aug 03, 2022 at 12:56 PM)

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Scientists have discovered dark matter around galaxies that existed about 12 billion years ago, the earliest detection yet of this mysterious substance that dominates the universe.

The findings, achieved by a collaboration led by researchers from Japan's Nagoya University, suggest that dark matter in the early universe is less 'clumpy' than predicted by many current cosmological models. If further work confirms this theory, it could change scientists' understanding of how galaxies evolve and suggest that the fundamental rules governing the cosmos could have been different when the 13.7 billion-year-old universe was just 1.7 billion years old.

The key to mapping dark matter in the very early universe the cosmic microwave background (CMB), a sort of fossil radiation left over from the Big Bang that is distributed throughout the entire cosmos.

"Look at dark matter around distant galaxies? It was a crazy idea. No one realized we could do this," University of Tokyo professor Masami Ouchi said in a statement. "But after I gave a talk about a large distant galaxy sample, Hironao came to me and said it may be possible to look at dark matter around these galaxies with the CMB."

Because light takes a finite time to travel from distant objects to Earth, astronomers see other galaxies as they existed when the observed light left them. The more distant a galaxy, the longer the light has been traveling to us and thus the further back in time we see them, so we see the most distant galaxies as they were billions of years ago, in the infant universe.

Observing dark matter is even trickier. Dark matter is the mysterious substance that makes up around 85% of the total mass of the universe. It doesn't interact with matter and light like the everyday matter made of protons and neutrons that fills stars, planets and us.  

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