Dark energy, the mysterious force apparently behind the accelerating expansion of the universe, is spreading evenly through space and time, suggest new findings.
The results also better constrain the amount of energy and matter in the universe. dark energy account, the study team said.
They reached their conclusions after analyzing the observations of cluster of galaxies made by the eROSITA X-ray instrument, which searches the entire sky above the Earth for these discovery-to-discovery collections galaxies. eROSITA is mounted on Spektr-RG, a Russian-German space telescope launched into Earth orbit in 2019.
Related: Dark matter and dark energy: the mystery explained (infographic)
Galaxy clusters are useful for understanding dark energy because, on a large scale, this strange repulsive “anti-gravity” force should suppress the formation of huge cosmic structures. This means that dark energy determines how and where clusters of galaxies, the largest objects in the universecan form.
“We can learn a lot about the nature of dark energy by counting the number of galaxy clusters formed in the universe over time,” study co-author Matthias Klein, an astrophysicist at Ludwig-Maximillians- University of Munchen in Germany (LMU), said in a press release (opens in a new tab).
The eROSITA Final Equatorial-Depth Survey (eFEDS) found around 500 galaxy clusters, one of the largest samples of low-mass galaxy clusters discovered to date. The observed clusters cover approximately the last 10 billion years of the evolution of the 13.8 billion year old universe.
The study team combined observations from eROSITA with optical data from the strategic Hyper Suprime-Cam Subaru program. This allowed the first cosmological study performed using clusters of galaxies detected by eROSITA.
The results of the study were then compared with theoretical predictions, confirming that dark energy accounts for about 76% of the total energy density of the universe. The results also suggest that this energy density is uniform in space and constant over time.
The team’s results agree well with other independent approaches to studying dark energy, such as previous studies of galaxy clusters as well as those using an effect of gravity on light called weak gravitational lens. Yet while new findings shed more light on dark energy, this force remains a mystery that physicists are eager to delve into.
Why is dark energy so problematic?
In the 1920s, the American astronomer Edwin Hubble made observations of distant galaxies that showed they were moving away from us. Also, the further away a galaxy is, the faster it is moving away, leading scientists to discover that the universe is expanding.
It was quite shocking, overturning the widespread idea at the time that the universe existed in a stable, steady state. Things got stranger in 1998, when sightings of distant supernova showed that not only is the universe expanding, but that expansion is accelerating.
“To explain this acceleration, we need a source, and we call this source ‘dark energy’, which provides a kind of ‘anti-gravity’ to accelerate cosmic expansion,” said the co- Study author Joe Mohr, an LMU. astrophysicist.
Yet despite knowing what dark energy does and being able to calculate that it makes up about 76% of the energy and matter in the universe, scientists still don’t know what it is. she really is, or why she began to act on the universe in her later epochs.
The effect of dark energy causing accelerated expansion in the later universe, after the initial rapid expansion of the universe following the big Bang completed, is something like applying an initial push to a child on a swing. As the child slows to a stop, the swing begins to pick up speed again, without another push. Not only that, but it accelerates faster and faster and reaches greater and greater heights.
Much like the swing analogy, the accelerating expansion of the universe tells scientists that something is missing in their image of the cosmos.
“Although the current errors in dark energy constraints are even larger than we would like, this research uses a sample of eFEDS which, after all, occupies an area less than 1% of the full sky,” added Mohr. “The nature of dark energy has become the next Nobel Prize-winning problem.”
The team’s research was published last month in the journal Royal Astronomical Society Monthly Notices (opens in a new tab).
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