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Scientists map all of the matter in the universe

When the universe began about 13 billion years ago, matter was flung outward and gradually formed the stars, planets, and galaxies that we know today. Now, a team of scientists led by the University of Chicago has carefully assembled the most comprehensive map to date of how matter spread and is distributed throughout the universe following the Big Bang. 

The analysis revealed that matter may not be as “clumpy” as expected from current models of the universe, thus adding to a body of evidence that there may be something missing from our existing standard models.

To construct this map, the researchers combined data from two different telescope surveys: The Dark Energy Survey, which examined the sky over a period of six years from a mountaintop in Chile, and the South Pole Telescope, which searches for the faint traces of radiation that are still traveling across the sky from the beginning of the universe.

Combining these two methods reduces the risk that the results are skewed by an error in one of the forms of measurement. “It functions like a cross-check, so it becomes a much more robust measurement than if you just used one or the other,” said UChicago astrophysicist Chihway Chang, one of the lead authors of the studies documenting the findings.

In both cases, the scientists examined a phenomenon called “gravitational lensing,” which refers to the fact that, as light travels across the universe, it can be slightly bent while passing high-gravity objects such as galaxies. This method catches both regular and dark matter (a mysterious form of matter that experts have managed to detect only indirectly, through its effects on regular matter), since both types of matter exert gravity.

By comprehensively analyzing the two data sets, the scientists could infer where all the matter ended up in the universe. While the majority of the results fit perfectly with the currently accepted model of the universe, a surprising new finding that deviates from the model is that the universe appears to be less “clumpy” – or clustering in certain areas rather than evenly spreading out – than the standard model would predict. Further research is needed to clarify this issue and untangle its consequences to our current understanding of the vast world in which we live.

“I think this exercise showed both the challenges and benefits of doing these kinds of analyses. There’s a lot of new things you can do when you combine these different angles of looking at the universe,” Chang concluded.

The three studies documenting these findings are published in the journal Physical Review D.

Image Credit: Photo by Andreas Papadopoulos


By Andrei Ionescu, Staff Writer

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