The universe's expansion may actually have started to slow rather than accelerating at an ever-increasing rate as previously thought, a new study suggests.
"Remarkable" findings published today in Monthly Notices of the Royal Astronomical Society cast doubt on the long-standing theory that a mysterious force known as 'dark energy' is driving distant galaxies away increasingly faster.
Instead, they show no evidence of an accelerating universe.
If the results are confirmed it could open an entirely new chapter in scientists' quest to uncover the true nature of dark energy, resolve the 'Hubble tension', and understand the past and future of the universe.
Lead researcher Professor Young-Wook Lee, of Yonsei University in South Korea, said: "Our study shows that the universe has already entered a phase of decelerated expansion at the present epoch and that dark energy evolves with time much more rapidly than previously thought.
"If these results are confirmed, it would mark a major paradigm shift in cosmology since the discovery of dark energy 27 years ago."
The Hubble residual diagram before (top) and after (bottom) the age-bias correction. Corrections are applied to supernova data from the Dark Energy Survey project. After correction, the dataset no longer supports the ΛCDM model (red line) with a cosmological constant, but instead more closely fits with a time-varying dark energy model favoured by a combined analysis using only baryonic acoustic oscillations and cosmic microwave background data (blue line). Son et al. Licence type Attribution (CC BY 4.0)
This diagram shows how the universe appears to be in a state of decelerated expansion (red line). The dotted vertical line marks the present epoch, while the black line shows the ΛCDM prediction. The green and red lines represent the new study’s model before (green) and after (red) age-bias correction, consistent with baryonic acoustic oscillations and cosmic microwave background data (blue line). Son et al. Licence type Attribution (CC BY 4.0)
For the past three decades, astronomers have widely believed that the universe is expanding at an ever-increasing rate, driven by an unseen phenomenon called dark energy that acts as a kind of anti-gravity.
This conclusion, based on distance measurements to faraway galaxies using type Ia supernovae, earned the 2011 Nobel Prize in Physics.
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