An international team of scientists has published the most accurate map of all matter in the universe obtained to date, including the invisible dark matter, which makes up 75% of everything in the cosmos. The results, however, showed differences between observation and prediction.
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The team used data from two major gravitational lensing surveys: the Dark Energy Survey, which collected data in near-ultraviolet, visible, and near-infrared wavelengths; and the South Pole Telescope, which observes the cosmic microwave background.
By comparing these two datasets, scientists obtained a huge map of distributed matter in the universe. “It works like a cross-check, making it a much more robust measure than if you just used one or the other,” said astrophysicist Chihway Chang of the University of Chicago.
Gravitational lensing, one of the main sources of Dark Energy Survey data used in this research, is formed by massive galaxies positioned in the path between Earth and even more distant galaxies. When this alignment occurs, light from the background object is magnified and distorted by the gravity of the nearest galaxy.
The cosmic background radiation is the fossil “light” of the Big Bang, in the form of microwaves. Due to the expansion of the universe, the first photons scattered throughout the universe had their wavelengths “stretched” until they assumed the characteristics of microwave radiation. It is one of the main evidences of the Big Bang.
The map obtained by the new research also reveals the distribution of dark matter, the mysterious substance that “completes” the gravitational force observed throughout the universe. Without adding dark matter into astronomical models, the remaining mass of “ordinary”, i.e., visible, matter cannot explain the observations.
Now, physicists around the world will be able to use this map and compare it with models and simulations of the universe’s evolution to see if the observed matter distribution matches theoretical predictions. Some of these comparisons have already been made, and overall the map matches current models—but not quite.
According to the authors’ articles, the map’s matter distribution is less irregular than the models predict. While not exactly a surprise—scientists know there are a few things missing from the theory—more work will have to be done to fine-tune the predictions with these observations.
The research was published in Physical Review D and yielded three articles available on the arXiv.org server.
Source: arXiv.org (1, 2, 3); via: EurekAlert