Is the expansion of the Universe slowing down: a new debate in cosmology

Astrophysicists from Yonsei University in South Korea have reignited one of the most intense scientific debates in modern cosmology with a new study published in the Monthly Notices of the Royal Astronomical Society. The scientists argue that the critical articles written against their sensational hypothesis published last year contain serious methodological errors, which could alter perceptions regarding the expansion of the Universe. This is reported by Ixbt.com reports .

According to ixbt.com, at the end of last year, the South Korean team analyzed Type Ia supernovae, which are considered standard candles for measuring distances. At that time, the scientists announced that after introducing corrections for stellar age, the expansion of the Universe might have shifted from acceleration to deceleration. If confirmed, this would imply that dark energy, which is considered the cause of the Universe's acceleration, is not constant but evolves over time, undermining the fundamental principles of the Lambda-CDM standard cosmological model.

Response to criticism and methodological disputes

In June of this year, an international group of researchers from the University of Southampton published a rebuttal, stating that the correlation between the age of supernovae and their luminosity is very weak. In their view, the correction proposed by the Korean scientists is too small to refute the model of the Universe's accelerating expansion. However, the Yonsei University group responded scientifically to this criticism, demonstrating that the opponents themselves made errors.

The main objection is that the critics used a very wide redshift range (0.04 < z < 0,42) olingan oʻta yangi yulduzlarni birlashtirib oʻrgangan. Bunday oraliqda asosiy galaktikalarning oʻrtacha yoshi taxminan 3 milliard yilga oʻzgarib ketadi. Tadqiqot rahbari doktor Chul Chxungning taʼkidlashicha, opponentlar koʻrsatib oʻtgan yosh siljishining qiyaligi aynan shu metodologik muammo natijasidir, tegishli qizil siljish oraligʻi cheklanganda esa yoshga bogʻliqlik yana kuchayadi.

Future observations and the decisive test

The second contentious issue relates to recalculating the age of host galaxies to the age of the supernovae's progenitors. Although critics claim this evolution is not very significant, the authors of the response article show that this very effect makes the age-luminosity graph significantly steeper. When both factors are taken into account, the final correction for cosmological calculations remains unchanged.

Furthermore, the corrected results for supernovae are consistent with independent data on baryon acoustic oscillations obtained using the DESI (Dark Energy Spectroscopic Instrument). In the scientists' opinion, this once again points to the evolutionary nature of dark energy.

The authors openly admit that their work cannot be considered absolute proof that cosmic acceleration has stopped. However, this study has once again brought to the center of discussion how systematic errors in interpreting Type Ia supernovae affect the most important measurements in cosmology. In the coming months, the Vera Rubin Observatory is expected to begin operations, and its broader and more uniform selection of supernovae is expected to provide full clarity on this issue.