We know the universe is expanding. What we do not know is why it appears to be doing so considerably faster than our best models predict. And it seems one study suggests the gap in our understanding could be more dramatic than we thought.
An international team of 40 astronomers, including researchers from NSF NOIRLab and the Space Telescope Science Institute, combined different methods of measuring the universe's expansion rate for an accurate reading.
Known as the Local Distance Network, the team studied red giant stars of known brightness, analysing exploding stars and examining different galaxies.
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Across all these methods, they found a consistent universe expansion rate of 73.5 kilometres per second per megaparsec (roughly 3.26 million light-years).
However, this is much faster than early universe predictions, which say the universe is expanding at about 67 or 68 kilometres per second per megaparsec. The team say this marks a 'significant shift in perspective' and claims there is a need for a 'deeper reassessment' of the early universe.
The findings were published in the journal Astronomy & Astrophysics.
Although the difference between the values appears small, it exceeds statistical uncertainty and is known as the 'Hubble tension.'
"This work effectively rules out explanations of the Hubble tension that rely on a single overlooked error in local distance measurements," the authors wrote in the paper. "If the tension is real, as the growing body of evidence suggests, it may point to new physics beyond the standard cosmological model."
According to the researchers, the current models might fail to account for the influence of dark energy, new particles, or changes in gravity.
"The Hubble tension may not be the result of measurement error, but rather evidence that the current model of the universe is missing a key component," the researchers added. "With next-generation observatories expected to provide even more precise measurements, astronomers aim to determine whether this discrepancy will ultimately be resolved or continue to point toward new physics."
If accurate, this increasing 'dark energy' could cause the universe to expand so far that the overwhelming gravity causes it to collapse in on itself.
Scientists refer to it as the 'Big Crunch' theory and it means the collision of stars and galaxies would compress into a scorching, dense core, and ultimately all of space, time, and existence would be consumed in a single catastrophic implosion.