In 1998, scientists came across a startling cosmic truth. Not only is the universe expanding, they realized, but it also seems to be accelerating over the years, accelerated by a force we cannot see.
This mysterious influence would soon become known as dark energy, one of the greatest puzzles in physics.
This would complement the equally, if not more, confusing aspect of our universe called dark matter, a general concept first highlighted by scientists in 1933 to describe all that constitutes the hidden halo-like barriers preventing galaxies to just collapse. (Yet another force that we cannot understand with human eyes.)
But even though we are unable to grasp the elusive nature of dark matter and dark energy with sight, we are able to measure it with mathematics. And on Wednesday, in a series of articles in the Astrophysical Journal, astrophysicists succeeded in imposing the most precise limits yet on the composition and evolution of our universe, including the dark universe.
Using a powerful analytical mechanism dubbed Pantheon+, the team discovered that the cosmos is made up of roughly two-thirds dark energy and one-third matter, mostly in the form of dark matter. Specifically, they suspect that 66.2% of the universe manifests as dark energy, while the remaining 33.8% belongs to both dark and visible matter.
Even more exciting than the outcome of Pantheon+ may be the mind-blowing way it works. In short, the team harnessed an array of powerful cosmic flashlights to turn back time and document the contents of the universe as it was more than 10 billion years ago.
By “flashlights” I mean type 1a supernovae.
These starbursts are so bright that they eclipse entire galaxies and are therefore seen billions of light-years from Earth. They’re like flashlights, but instead of illuminating a long hallway, they illuminate the endless tunnel of space and time. In fact, they are essential to the discovery of the dark universe, helping to discover the existence of dark matter in 1933 and dark energy in 1998.
Pantheon+ has taken things to the next level. The scientists behind the analysis focused on more than 1,500 supernovae which, when combined, collectively illuminate about three-quarters of the known universe. Wow, indeed.
A timeline of the universe.
Nasa
“With this combined Pantheon+ dataset, we get an accurate view of the universe from when it was dominated by dark matter to when the universe became dominated by dark energy,” Dillon Brout , an astronomer at the Harvard-Smithsonian Center for Astrophysics, said in a statement.
“This dataset is a unique opportunity to see dark energy activate and drive the evolution of the cosmos on the largest scales through present time,” Brout said.
This might settle some scientific debates
Down the road, the Pantheon+ legacy is about to transcend the Dark Universe.
As a bonus, the analytical tool also confirmed that the cosmos is truly expanding at an accelerating rate, and it offered extremely promising evidence in support of a cornerstone of scientific thought: the Standard Model of particle physics.
This framework describes roughly how each known particle behaves independently, as well as with each other, and even serves as the basis for many prominent theories regarding what the Dark Universe really is.
A picture of the particles in the Standard Model.
Fermilab
“We are able to put the most precise constraints on the dynamics and history of the universe to date,” Brout said. “We’ve combed through the data and can now say with more confidence than ever before how the universe has evolved over the eons and that today’s best theories of dark energy and dark matter hold up.”
In other words, Pantheon+ could be telling us that we should conclude some alternative theories on dark matter and dark energy. unconnected to the standard model. These theories could be, well, incorrect.
Additionally, we also have to talk about my personal favorite consequence of the Pantheon+ datasets. Finally, it could help put an end to a long-running, rather heated, debate among physicists.
We may finally be on the way to decoding what is called the Hubble constant. Kind of.
Basically, we know the universe is expanding exponentially. We can literally see it happening in real time. But scientists can’t agree on the exact rate at which this expansion is occurring. The key to the solution is the Hubble constant, but different ways of calculating this constant seem to give different answers.
The arcs and ridges of the galaxy cluster Abell 370 reveal “gravitational lensing”, the distortion of light from distant background galaxies by the cluster’s gravitational field. The lensing effect helps astronomers measure the distribution of dark matter in galaxy clusters.
NASA, ESA and the Hubble SM4 ERO team
Although after pooling the Pantheon+ sample with data from another scientific collaboration, a Harvard press release says we may now have the tightest local measure of the current expansion rate of the universe. . (The keyword here is “local”. That will come later.)
In a nutshell, the collaboration found the Hubble constant to be 73.4 kilometers (45.6 miles) per second per megaparsec (km/s/Mpc) with an astonishing 1.3% uncertainty.
“In other words, for every megaparsec, or 3.26 million light-years, the analysis estimates that in the near universe, space itself is expanding at over 160,000 miles per hour. “, explains the press release. This figure, for context, falls right in the middle of the historic 2001 measurement of 72 km/s/Mpc and later reports of 74 km/s/Mpc.
It is however damn far from another advanced measurement which suggests a constant of 69.8 km/s/Mpc.
OK, yes, there is still a gap. And, again, Pantheon+’s constant is based on “local” measurements.
Thus, the Pantheon+ team points out that “observations from a totally different time in the history of the universe predict a different story”. So, in a way, having a new contrasting Hubble constant could not solve the Hubble tension, but rather intensify the already tense debate? Like I said, it’s complicated.
A simulation of dark matter filaments across the universe.
Zarija Lukic/Lawrence Berkeley National Laboratory
“We thought it would be possible to find clues to a new solution to these problems in our data set, but instead we find that our data rules out many of these options and that deep divergences remain just as stubborn. than ever,” Brout said. .
But ultimately, because Pantheon+’s results are so perfect, they might at least elucidate where the point of contention lies in Hubble’s ongoing debate.
“Many recent theories have started pointing to exotic new physics in the very early universe,” Brout said. “However, such untested theories must withstand the scientific process, and the Hubble strain continues to be a major challenge.”
Physics is full of tricky puzzles and puzzles and, honestly, roadblocks. But I like to imagine these obstacles as motivation to advance the field and turn the minds. This is why Pantheon+’s was innovated in the first place.
And with this mechanism, we have absolutely moved forward in dissecting the truth about the dark side of our universe – at the very least. Or as Brout puts it, “Pantheon+ gives us our best chance yet to constrain dark energy, its origins and evolution.”
#supernovae #ultraprecise #calculation #dark #universe