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Planets, stars, and other cosmic objects are made up of matter., as are the atoms that exist even in our own bodies. But matter is not all that makes up the universe, and on the cosmic scale it is difficult to determine exactly how much is normal matter and how much is something else.
In a team of scientists at the University of California, Riverside claim that they have made the most accurate measurement of the amount of normal matter in the universe, and it is simply 31.5 percent.
Their research is detailed in a study published this week in The Astrophysical Journal. The findings could help scientists understand how the universe evolved and what the rest is made of.
Scientists believe that the universe is made up of three things: normal matter, dark matter, and dark energy. Normal matter is the atoms that make up all cosmic objects in the universe, yet it represents the smallest proportion of the cosmos.
In fact, most of the universe is made up of dark energy. Dark energy is theorized to make up about 70 percent of the universe, but despite its abundance, dark energy has never been directly observed or measured.
Dark matter represents the rest of the universe. It is the missing mass that holds all matter, galaxies, and stars in place through its gravitational force.
Due to the mysterious and, well, dark nature of dark energy and dark matter, it is difficult to determine exactly what part of the universe they represent.
To calculate the amount of normal matter in the universe, the team behind the new study looked at the largest structures in the cosmos: galaxy clusters.
Galaxy clusters consist of hundreds or thousands of galaxies, held together by gravity. They are formed from matter that has collapsed over billions of years under the weight of its own gravity, so the number of clusters observed today correlates with the total amount of matter in the universe.
“A higher percentage of matter would lead to more clusters,” Mohamed Abdullah, a graduate student in UCR’s department of physics and astronomy and lead author of the new study, said in a statement. “The ‘Goldilocks’ challenge for our team was to measure the number of clusters and then determine which answer was ‘correct’.”
The team behind the new study created a catalog of galaxy clusters and compared the number of clusters in their catalog with simulations of clusters to determine the total amount of normal matter. In doing so, they calculated that the best combined value of normal matter is 31.5 percent of the total amount of matter and energy in the universe.
The remaining 68.5 percent is dark energy., according to the study.
Understanding dark energy is critical to understanding the universe. This dark force is responsible for the acceleration of the expansion of the universe, separating the galaxies with its strong gravitational force.
As scientists get a better idea of the expansion rate of the universe, they will also get a better idea of how the universe evolved over time and where it all began.
Abstract: We derived cosmological constraints on the density of matter, and the amplitude of fluctuations, using a catalog of 1800 galaxy clusters that we identified in the Sloan Digital Sky Survey-DR13 spectroscopic dataset using our GalWeight technique to determine cluster membership. When analyzing a subsample of 756 clusters in a redshift range of 0.045 ≤ with ≤ 0.125 and virial masses of SUBWAY ≥ 0.8 × 1014 with medium redshift of with = 0.085, we obtain (systematic) and (systematic), with a cluster normalization relationship of. There are several unique aspects to our approach: we use the largest spectroscopic dataset currently available, and we assign membership using the GalWeight technique, which we have shown to be very effective in simultaneously maximizing the number of genuine cluster members and minimizing the number of intruders. pollutants. In addition, instead of using scale relationships, we calculate the masses of the clusters individually using the virial mass estimator. Since it is a catalog of low-redshift clusters, it is not necessary to make assumptions about the evolution of either the cosmological parameters or the properties of the clusters themselves. Our limitations on and are consistent and highly competitive with those obtained from non-cluster cosmological abundance probes, such as the cosmic microwave background, baryonic acoustic oscillation (BAO), and supernovae. The joint analysis of our cluster data with Planck18 + BAO + Pantheon gives y.
