Analysing satellites of massive galaxy groups suggests younger Universe, study finds

PTI, Jan 24, 2024, 8:58 AM IST

New Delhi: A research that studied satellites around massive galaxy groups suggests that the Universe may be younger than predicted by the standard cosmological models.

According to these standard models, cosmological structures begin to form with the emergence of small structures, which upon subsequent merging go on to form larger systems, such as massive galaxy groups or clusters.

The findings of this study from the National Astronomical Observatories of the Chinese Academy of Sciences, China, therefore, challenged the current cosmological model, the researchers said.

The findings may also provide valuable insights into the Hubble tension problem, they said. The Hubble tension stems from the disagreement between two different methods of measuring the universe’s rate of expansion – the Hubble constant – that produces two different answers.

In this study, the researchers analysed the motions of satellite pairs around massive galaxy groups, as they said that could provide valuable insights about the assembly of the galaxy groups, and thus the age of the Universe. They used public data from the Sloan Digital Sky Survey (SDSS).

The SDSS is one of the largest, most detailed, and most often cited astronomical surveys ever existed and its goal is to expand the understanding of the universe, the formation of stars and galaxies, among others, according to its website.

The researchers investigated the movement of satellite pairs positioned on the opposite side of massive galaxy groups by using their velocity offsets from the central galaxy along the line of sight. They discovered a notable excess of pairs exhibiting correlated velocity offsets compared to pairs displaying anti-correlated velocity offsets.

‘The excess of correlated satellite pairs suggests the presence of recently accreted or infalling satellite galaxies,’ said Qi Guo, the corresponding author of the paper published in the journal Nature Astronomy.

They also found this excess in up-to-date cosmological simulations but with a considerably lower magnitude than in observations.

They said that the significant discrepancy between the observations and simulations implied that these massive galaxy groups were younger in the real Universe.

‘Since the age of the massive galaxy groups could be closely related to the age of the Universe, these findings consequently suggest a younger Universe compared to that derived from the cosmic microwave background (CMB) by the Planck Collaboration,’ said Qing Gu, first author of the paper.