Dark energy, the mysterious force apparently driving the accelerating expansion of the universe, is spread evenly through space and time, latest results suggest.
The findings also higher constrain how much of the universe’s energy and matter content dark energy accounts for, the study team said.
They reached their conclusions after analyzing observations of galaxy clusters made by the eROSITA X-ray instrument, which searches the complete sky over Earth for these find-to-find collections of galaxies. eROSITA is mounted on Spektr-RG, a Russian-German space telescope that launched to Earth orbit in 2019.
Galaxy clusters are useful for understanding dark energy because, on large scales, this odd repellant “anti-gravity” force should suppress the formation of enormous cosmic structures. Meaning dark energy determines how and where galaxy clusters, the most important objects in the universe, can form.
“We are able to learn an excellent deal in regards to the nature of dark energy by counting the variety of galaxy clusters formed within the universe as a function of time,” study co-author Matthias Klein, an astrophysicist at Ludwig-Maximillians-Universitat Munchen in Germany (LMU), said in a press release (opens in latest tab).
The eROSITA Final Equatorial-Depth Survey (eFEDS) found about 500 galaxy clusters, one among the most important samples of low-mass galaxy clusters discovered so far. The observed clusters cover roughly the past 10 billion years of the 13.8 billion-year-old universe’s evolution.
The study team combined the eROSITA observations with optical data from the Hyper Suprime-Cam Subaru Strategic Program. This enabled the primary cosmological study performed using galaxy clusters detected by eROSITA.
The outcomes of the study were then in comparison with theoretical predictions, confirming that dark energy accounts for around 76% of the full energy density of the universe. The findings also suggest that this energy density is uniform in space and constant in time.
The team’s results agree well with other independent approaches to the investigation of dark energy, corresponding to previous galaxy cluster studies in addition to those using an effect of gravity on light called weak gravitational lensing. Yet, while the brand new findings shed more light on dark energy, this force stays a mystery that physicists are desirous to unravel.
Why is dark energy so problematic?
Within the Twenties, American astronomer Edwin Hubble made observations of distant galaxies that showed they’re receding from us. As well as, the farther away a galaxy lies, the quicker it’s moving away, which led scientists to find that the universe is expanding.
This was shocking enough, overturning the commonly held idea on the time that the universe existed in a stable regular state. Things got weirder in 1998, when observations of distant supernovas showed that, not only is the universe expanding, but this expansion is accelerating.
“To clarify this acceleration, we want a source, and we discuss with this source as ‘dark energy,’ which provides a type of ‘anti-gravity’ to hurry up cosmic expansion,” said study co-author Joe Mohr, an LMU astrophysicist.
Yet, despite knowing what dark energy does and having the ability to calculate that it comprises around 76% of the energy and matter within the universe, scientists still are in the dead of night about what it actually is, or why it began acting on the universe in its later epochs.
The effect of dark energy causing accelerating expansion within the later universe, after the initial rapid expansion of the universe consequently of the Big Bang ended, is something like applying an initial push to a toddler on a swing. Because the child slows toward a halt, the swing starts to choose up speed again, with none further push. Not only that, but it surely accelerates faster and faster and reaches increasingly greater heights.
Similar to the swing analogy, the accelerating expansion of the universe tells scientists that something is missing from their picture of the cosmos.
“Although the present errors on the dark energy constraints are still larger than we would need, this research employs a sample from eFEDS that, in any case, occupies an area lower than 1% of the total sky,” added Mohr. “The character of dark energy has change into the following Nobel Prize-winning problem.”
The team’s research was published last month within the journal Monthly Notices of the Royal Astronomical Society (opens in latest tab).