When the universe began after the big bang, the matter in the universe was very hot. This matter spread outward, cooled, gradually clumped together and gradually formed planets.
Scientists are very interested in tracking the journey of this matter because they can try to replicate what happened and what forces were at work by seeing where it all ended up.
For this, scientists need a lot of data collected with telescopes.
A group of scientists, including some from the University of Chicago and the Fermi National Accelerator Laboratory, have made one of the most accurate measurements ever made of how matter is distributed throughout the Universe today. Scientists combined data from two major telescope surveys of the Universe, the Dark Energy Survey and the South Pole Telescope.
UChicago astrophysicist Chihway Chang, one of the lead authors on the studies, said: “It works like a cross-check, so it becomes a much more robust measurement than if you just used one or the other.”
In both cases, the analysis examined a phenomenon known as gravitational lensing. As light traverses the cosmos, it can experience a slight bend as it passes galaxies and other objects with strong gravity.
Because both ordinary matter and dark matter are subject to gravity, this method captures both ordinary matter and dark matter.
The scientists were able to determine where all the matter ended up in the universe by carefully analyzing these two sets of data. It is more accurate than previous measurements, narrowing the range of possible outcomes for this situation. Most of the results fit perfectly with the currently accepted best theory of the universe.
Analysis co-author and University of Hawaii astrophysicist Eric Baxter said: “But there are also signs of a crack – one that has also been suggested by other analyzes in the past. It seems that there are slightly fewer fluctuations in the current Universe than we would predict, assuming our standard cosmological model anchored in the early universe.”
Scientists noted, “In particular, today’s measurements show that the universe is less ‘lumpy’ — clustering in certain areas rather than evenly spread out — than the model would predict. If other studies continue to find the same results, it could mean something is missing in our existing model of the universe. Yet the results are not yet at the statistical level that scientists consider rock solid. That requires further study.”
More than 150 researchers were involved in the analysis. It is a milestone because it provided useful information from two telescope surveys. This is a long-awaited strategy for the future of astrophysics as more large telescopes come online in the coming decades, but few have been implemented yet.
- Y. Omori, EJ Baxter, et al. Joint analysis of DES Year 3 data and CMB lensing from SPT and Planck I: construction of CMB lens maps and modeling choices. Physical Assessment D DOI: 10.48550/arXiv.2203.12439
- C. Chang, Y. Omori, EJ Baxter, et al. Joint analysis of DES Year 3 data and CMB lensing of SPT and Planck II: cross-correlation measurements and cosmological constraints. Physical Assessment D. DOI: 10.48550/arXiv.2203.12440
- TMC Abbott, M. Aguena, A. Alarcon, et al. Joint analysis of DES Year 3 data and CMB lenses from SPT and Planck III: combined cosmological constraints. Physical Assessment D. DOI: 10.48550/arXiv.2206.10824