A survey of more than 25 million galaxies has uncovered strange inconsistencies in the way astronomers measure the clumpiness of the universe, which could threaten the Standard Model of cosmology, which describes how the universe formed and evolved.
The difference, discovered by measuring the distortion of light caused by the powerful gravitational fields of distant galaxies, suggests the universe is less crowded than previously predicted.
If the measurement is accurate, it would join the Hubble tension as another major challenge to our preconceptions about how the universe evolved—a challenge that could give way to new physics or even entirely different models of the universe.The researchers published their findings Dec. 11 in the journal Physical Review D.
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“We’re still being pretty cautious here,” Michael Strausschair of the Department of Astrophysics at Princeton University and one of the leaders of the team that made the discovery, said in a statement. “We are not saying that we have just discovered that modern cosmology is all wrong. Statistics show that there is only a one in 20 chance that it is just due to chance, which is compelling but not entirely certain. But as we do in The astronomical community has come to the same conclusion through multiple experiments, and as we continue to make these measurements, maybe we’ll find that it’s true.”
According to the Standard Model of Cosmology, after big Bang The young universe was a boiling soup of plasma that began to rapidly expand due to an invisible force called gravity. dark energy.As the universe grew, ordinary matter interacting with light condensed around invisible clumps dark matter Create the first galaxy, connected by a huge cosmic web. Today, cosmologists believe that ordinary matter, dark matter and dark energy make up about 5%, 25% and 70% of the universe respectively.
However, this picture is increasingly problematic. To test their models, astronomers often compare the past universe to the present. Their past measurements were derived from the cosmic microwave background (CMB), the static hiss of the universe’s first light that left its source (recombined atoms) 380,000 years after the Big Bang.
However, the Hubble constant predicted by the CMB—a value that tracks the expansion rate of the universe—is inconsistent with calculations of objects in the contemporary universe. This discrepancy leads to a cosmological crisis known as the Hubble tension.
The new differences about the lumpiness of the universe center on a number called S8, which measures how much matter is clumped, or clumped together, in the entire universe. After using the Planck satellite to study the cosmic microwave background (CMB), astronomers previously plugged the data into the Standard Model of Cosmology. The predicted value of S8 is 0.83.
This conflicts with new measurements of S8 using Japan’s Subaru telescope, which looked at how much the light is distorted by the presence of matter in the galaxy. The researchers arrived at a smaller value of 0.77 for S8. The new results are replicated by two other collaborative projects that use gravitational lensing to map matter in the universe: the Dark Energy Survey and the Thousand-Degree Survey, making separate anomalous results unlikely.
“We are confirming the growing belief in the community that there are real differences between measurements of reunion in the early universe (measured from the cosmic microwave background) and measurements of the galactic era ‘only’ 9 billion years ago,” Allen said in the analysis Kannawadi, an associate research scholar at Princeton University, said in a statement.
Although this question points to another big hole in our understanding of the universe, cosmologists don’t yet have a good way to fill it. Cosmologists may be wrong about the amount of dark matter in the universe or how it clumps together. Perhaps dark energy has changed over the course of the universe’s life—an explanation that could be addressed through adjustments to the Standard Model of Cosmology to account for S8 and the Hubble tension.
Or, most excitingly, it could mean the standard model is damaged and needs to be replaced entirely. To make sure, scientists will take more precise measurements with more powerful telescopes. Two of the contenders are Chile’s Vera Rubin Observatory and the Nancy Grace Roman Space Telescope, which will come online in 2025 and 2027 respectively.
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