Matter found to comprise 31% of the total amount of matter and energy in the universe

"How much matter exists in the universe?" is one of the most intriguing and significant topics in cosmology. Now, for the second time, the whole amount of matter has been successfully measured by an international team that includes experts from Chiba University. According to their findings, which were published in The Astrophysical Journal, matter makes up 31% of all matter and energy in the universe, with dark energy making up the remaining percentage.

Approximately 20% of matter is thought to be made up of regular or "baryonic" matter, which includes atoms, galaxies, stars, and life, according to cosmologists. Dr. Mohamed Abdullah, the first author, is a researcher at Chiba University's National Research Institute of Astronomy and Geophysics-Egypt in Egypt. Approximately 80% of it is composed of dark matter, which may include some as-yet-undiscovered subatomic particles despite its enigmatic nature being unknown.

Says co-author Gillian Wilson, a professor of physics and vice chancellor for research, innovation, and economic development at UC Merced, "the team used a well-proven technique to determine the total amount of matter in the universe, which is to compare the observed number and mass of galaxy clusters per unit volume with predictions from numerical simulations." Wilson was Abdullah's former graduate advisor.

"Cluster abundance," or the number of clusters currently observable, is very sensitive to cosmological circumstances, particularly the total mass of matter in the universe."

According to University of Virginia researcher Anatoly Klypin, "more clusters would be formed if a larger percentage of the total matter in the universe was present." "However, since the majority of the matter in a galaxy cluster is dark and invisible to telescopes, it is challenging to determine its mass with accuracy."

The group was compelled to employ an indirect tracer of cluster mass in order to get around this obstacle. Their reliance was based on the mass richness relation (MRR), which states that galaxies are more abundant in more massive clusters than in less massive clusters. Since galaxies are made up of bright stars, one may infer the entire mass of a cluster by counting the number of galaxies inside it.

The scientists estimated the overall mass of each cluster by counting the number of galaxies in each sample taken from the Sloan Digital Sky Survey. The measured number and mass of galaxy clusters per unit volume were then compared to estimates from computer models.

The cosmos that accounted for 31% of all matter was the best fit between simulations and observations; this estimate was in great agreement with that derived from cosmic microwave background (CMB) studies made by the Planck spacecraft. Interestingly, CMB is a whole another method.

According to Chiba University's Tomoaki Ishiyama, "We have succeeded in making the first measurement of matter density using the MRR, which is in excellent agreement with that obtained by the Planck team using the CMB method," "This study indicates that cluster abundance is a viable method for limiting cosmological parameters, and it can be used in conjunction with non-cluster approaches like gravitational lensing, Type Ia supernovae, baryon acoustic oscillations, and CMB anisotropies."

The group prides itself on being the first to accurately measure the distance to each cluster and the true member galaxies that are gravitationally bound to the cluster rather than background or foreground interlopers along the line of sight using spectroscopy, a technique that divides radiation into a spectrum of individual bands or colors.

In earlier attempts to use the MRR approach, the distances to each cluster and the neighboring galaxies that were genuine members were calculated using far less sophisticated and accurate imaging techniques, such as utilizing images of the sky taken at certain wavelengths.

In addition to showing that the MRR technique is an effective means of establishing cosmological parameters, the paper, which was published in The Astrophysical Journal, also describes how it can be used with new datasets that come from spectroscopic galaxy surveys, such as those carried out with the Subaru Telescope, eROSITA Telescope, James Webb Space Telescope, Dark Energy Survey, and large, wide, and deep-field imaging.