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Paris (AFP)- The most precise measurements ever made of the composition of the universe and its rate of expansion suggest “something is fishy” in our understanding of the cosmos, the astrophysicist who led the research said on Wednesday.
The comprehensive new study published in The Astrophysical Journal further confirmed that there is a significant discrepancy between two different ways of estimating the rate at which the universe is expanding.
The study indicates that about five percent of the universe is made up of what we might think of as normal matter, while the rest is made up of dark matter and dark energy, both of which remain shrouded in mystery. .
Dark energy, a hypothetical force causing the universe to expand at an ever-increasing rate, accounts for 66.2% of the cosmos, according to the study published in The Astrophysical Journal.
The remaining 33.8% is a combination of matter and dark matter, which is also unknown but may consist of an as yet unknown subatomic particle.
To arrive at the most precise limits ever set on the composition of our universe, an international team of researchers observed the explosion of stars called supernovae.
They analyzed light from 1,550 different supernovae, ranging from near us to more than 10 billion light-years away, when the universe was a quarter of its current age.
“We can compare them and see how the universe behaves and changes over time,” said Dillon Brout of the Harvard-Smithsonian Center for Astrophysics and lead author of the study, called Pantheon+.
Two decades of analysis
The study updated data from the Pantheon project a few years ago, eliminating possible problems and establishing more accurate calculations.
“This latest Pantheon+ analysis is the culmination of more than two decades of diligent efforts by observers and theorists around the world to decipher the essence of the cosmos,” said Nobel Prize-winning American astrophysicist Adam Reiss. of Physics 2011, in a press release.
It was by observing supernovae in the late 1990s that Reiss and other scientists discovered that the universe was not only expanding, but also at an increasing rate, which means galaxies are moving farther apart. others.
“It was like you were throwing a ball, and instead of the ball going down, it was going up and it kept accelerating,” Brout said of the surprise at the discovery.
Pantheon+ has also pooled data with supernova collaboration SH0ES to find what is believed to be the most accurate measure of the universe’s expansion rate.
They estimated that the universe is currently expanding at 73.4 kilometers per second every megaparsec, or 3.26 million light-years. That equates to about 255,000 kilometers (160,000 miles) per hour, according to a Harvard-Smithsonian statement.
But there is a problem.
– Hubble voltage –
Measurement of cosmic microwave background radiation, which can go back much further in time to around 300,000 years after the Big Bang, suggests the universe is expanding at a significantly slower rate – around 67 kilometers per megaparsec.
This discrepancy was called the Hubble tension, after American astronomer Edwin Hubble.
The Pantheon+ results raised the certainty of Hubble’s voltage above what’s known as the five sigma threshold, meaning the discrepancy “can no longer be attributed to luck,” it said. brout.
“It certainly indicates that potentially something is wrong with our understanding of the universe,” Brout told AFP.
Some possible and unverified theories of the gap could include another type of dark energy in the very early universe, primordial magnetic fields, or even that the Milky Way is in a cosmic vacuum, which could slow it down.
But for now, Brout said, “We as scientists thrive on not understanding everything.
“There is still potentially a major revolution in our understanding, potentially coming within our lifetime,” he added.
© 2022 AFP
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