According to foreign media reports, one of the ultimate goals of cosmology is to accurately measure the total amount of matter in the universe. Even the most proficient in mathematics will find this task extremely difficult. But a team of scientists at the University of California, Riverside has already done it.
According to their article published in the Astrophysical Journal, the team determined that matter accounts for 31% of the universe’s total matter and energy, and the rest is composed of dark energy.
Muhammad Abdullah, the first author of the paper and a graduate of the Department of Physics and Astronomy at the University of California, Riverside, said: “If all matter is evenly distributed throughout the universe, its average mass density will be equivalent to every cubic meter. There are only six hydrogen atoms like this. However, since we know that 80% of matter is actually dark matter, in fact, most matter is not composed of hydrogen atoms, but a matter that cosmologists have not yet understood.”
The research team determined that matter accounts for 31% of the universe’s total matter and energy. Cosmologists believe that about 20% of matter is composed of regular or “baryon” matter, including stars, galaxies, atoms, and life, while the remaining 80% is composed of dark matter. The mysterious nature of dark matter is unknown so far, but it may contain some undiscovered subatomic particles.
Abdullah explained that a mature method for determining the total amount of matter in the universe is to compare the observed number and mass of galaxy clusters per unit volume with the predicted results of numerical simulations. Since today’s galaxy clusters are composed of matter that has collapsed in the past billions of years under the action of their own gravity, the number of galaxy clusters currently observed is very sensitive to cosmological conditions—especially the total amount of matter. .
“A higher proportion of matter will bring about more galaxy clusters,” Abdullah said. “The challenge for our team is to measure the number of galaxy clusters and then determine which answer is’more correct’. But we are very It is difficult to accurately measure the mass of any galaxy cluster, because most matter is dark and we cannot observe it with a telescope.”
In order to overcome this difficulty, astronomers led by the University of California Riverside team took the lead in inventing “GalWeight”-a cosmological tool that uses the orbits of member galaxies to measure the mass of the galaxy cluster. The researchers then applied their tools to the observation data from the Sloan Digital Sky Survey Center to create “GalWCat19”, a publicly available catalog of galaxy clusters. Finally, they compared the number of galaxy clusters in the new catalog with the simulation results to determine the total amount of matter in the universe.
The team compared the number of galaxy clusters they measured with the predictions of numerical simulations to determine which answer was “more correct.”
“We have successfully used galaxy cluster technology to complete the most accurate measurement ever made,” said the co-author of the paper and Professor of Physics and Astronomy at the University of California, Riverside, Gillian Wilson. “In addition, this is also the basis for galaxy orbit technology. First use. The values obtained by this technology are consistent with those obtained using non-cluster technologies (such as cosmic microwave background anisotropy, baryon acoustic oscillation, Type Ia supernova or gravitational lensing).”
“The great advantage of using GalWeight galaxy orbit technology is that our team can determine the mass of each galaxy cluster individually without relying on indirect statistical methods,” said Antori Krippin, the third author of the paper.
By comparing their measurement results with the results obtained by teams using other measurement methods, the team at the University of California, Riverside can determine the best combination value and conclude that matter accounts for 31.5± of the total matter and energy of the universe. 1.3%.