To put it nicely, it can be challenging to measure the components of our universe. The enigmatic component that is causing the Universe to expand, dark energy, is understood to make up the majority of the matter-energy density of the Universe. And we are aware that all other matter—both light and dark—is matter.
It is difficult to calculate the ratios of these three accurately, but researchers now claim to have carried out one of the most exact measurements to date to ascertain the ratio of matter.
Their findings show that the matter-energy density of the Universe is composed of 31.5 percent conventional matter and dark matter. Dark energy makes up the remaining 68.5 percent.
Put into perspective, according to astronomer Mohamed Abdullah of the University of California, Riverside and the National Research Institute of Astronomy and Geophysics in Egypt, "that amount of matter would correspond to an average mass density equal to only about six hydrogen atoms per cubic metre if all the matter in the Universe were spread out evenly across space."
However, given that dark matter makes up 80% of all matter, most of it actually consists of a substance that cosmologists don't yet fully comprehend rather than hydrogen atoms.
In fact, comprehending dark energy is essential to our comprehension of the universe. It appears to be the force that drives the expansion of the Universe, the velocity of which has proven to be extremely difficult to narrow down past a certain point. We don't know what it is precisely; the word "dark" in the term relates to that mystery.
Our comprehension of the rate of expansion will improve if we have a better understanding of the overall evolution of the Universe. Therefore, limiting the characteristics of dark energy is a rather significant task for cosmology as a whole, and there are several approaches to accomplish so.
A technique used by Abdullah and his team was inspired by how objects move in galaxy clusters, which are collections of up to hundreds of galaxies that are gravitationally bonded together.
Galaxy clusters can be used to measure the amount of matter in the universe. This is due to the fact that they are composed of matter that has gravitationally gathered together during the course of the universe's estimated 13.8 billion year existence.
Counting clusters can provide a reliable measurement of the amount of matter present since they are highly sensitive to the amount of matter in a volume of space. But once more, doing it is not an easy task.
According to Abdullah, "a higher percentage of matter would result in more clusters."
"Our team's "Goldilocks" task was to count the clusters and then decide which response was "just right." However, since most of the stuff in galaxy clusters is dark and so invisible to telescopes, it is challenging to determine their precise mass."
With a method known as GalWeight, the team was able to solve this issue. With almost 98 percent accuracy, it can distinguish between galaxies that genuinely belong to a cluster and those that do not by looking at their orbits within and around that cluster. They claimed that doing so gives a more precise census of that cluster, which therefore results in a more accurate estimation of mass.
Astronomer Anatoly Klypin of New Mexico State University said, "A big benefit of employing our GalWeight galaxy orbit technique was that our team was able to calculate a mass for each cluster individually rather than relying on more indirect, statistical methods."
The group developed a list of galaxy clusters by using their method on observations obtained by the Sloan Digital Sky Survey. The total mass of the universe was then calculated by comparing these clusters to numerical simulations of galaxies.
The team's conclusion, which states that there is 31.5 percent matter and 68.5 percent dark energy, is quite similar to prior studies of the matter-energy density of the universe.
According to astronomer Gillian Wilson of UC Riverside, "We have succeeded in making one of the most precise measurements ever performed utilising the galaxy cluster technique."
Furthermore, this is the first instance of the galaxy orbit technique that has produced results that are comparable to those of groups that have utilised noncluster techniques including gravitational lensing, Type Ia supernovae, baryon acoustic oscillations, and cosmic microwave background anisotropies.
This outcome, according to the team, shows that GalWeight may prove to be a highly helpful tool for further exploring and constraining the cosmological characteristics of the Universe.
The Astrophysical Journal has published the research.
Comments
Post a Comment