Cosmological Standard Model Wrong? Universe's Expansion Slowing Down
For decades, it was assumed that the expansion of the universe was accelerating—a theory that won the Nobel Prize. Now, doubts are growing louder.
A Type Ia Supernova
(Image: NASA/ESA; CC BY 4.0)
The expansion of the universe may no longer be accelerating at all and has long “entered a phase of slowed expansion.” At least that's the opinion of a research group from South Korea, which has now presented the next study that casts doubt on the theory for which the Nobel Prize in Physics was awarded in 2011. As the team around Chul Chung from Yonsei University in Seoul now explains the team around Chul Chung from Yonsei University in Seoul explains, they have evidence that Type Ia supernovae do not have a consistent brightness after all. Instead, there is a connection between the age of the exploding stars and their brightness, which has led to a systematic error in distance measurement. If this is corrected, the fundamental picture of our universe's state changes.
Contradiction to the Cosmological Standard Model
Type Ia supernovae are considered “standard candles” because they are assumed to occur predictably and have a consistent brightness. For this reason, they have been systematically used for cosmic distance measurements over large distances, making them a foundation for human knowledge of the cosmos. As the Korean research group now explains, their analysis of 300 galaxies with such stellar explosions has shown with a probability bordering on certainty (99.999 percent) that the dimming of distant supernovae is due not only to cosmological effects but also to the properties of the stars themselves. If the systematic error is corrected, “the supernova data no longer fit the cosmological standard model.”
Those responsible point out that an independent review of their analysis is still pending. However, if it is successful, it would open a “completely new chapter” in the history of understanding dark energy that solves the mystery of the Hubble constant and contributes to understanding the past and future of the universe. It would be one of the most significant paradigm shifts in cosmology in decades. The research group itself is already working on analyses to confirm their discovery, and the initial results are promising. Furthermore, their data would fit well with a model developed within the DESI project. There, the first indications were discovered that the understanding of dark energy was wrong.
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After it was proven in the early 20th century, among others by Edwin Hubble, that the universe is expanding, research long assumed that this expansion was slowing down. It was only in 1998, through the analysis of distant supernovae, that it was discovered that the expansion was actually accelerating. This was awarded the Nobel Prize in Physics in 2011, but recently more and more doubts have arisen. Dark energy is said to be responsible for this acceleration, but its nature is mysterious. Like the DESI (Dark Energy Spectroscopic Instruments) team, the South Korean group now believes that the mysterious form of energy has “significantly” changed over the course of the universe's development.
However, the group also points out differences to the findings of the DESI collaboration. For example, they concluded that the expansion of the universe is still accelerating and that this would only change in the distant future. On the contrary, the new supernova measurements suggest that the acceleration has already ended. They also contradict the standard model of cosmology “with overwhelming significance.” The group is also relying on the expected data from the Vera C. Rubin Observatory, which is expected to observe and measure tens of thousands of galaxies with supernovae. The work from South Korea has now been published in the Monthly Notices of the Royal Astronomical Society.
(mho)
