According to conventional cosmological theories, the creation of small structures is the first step towards the construction of larger systems. These structures then integrate hierarchically. The biggest systems, enormous galaxy groups, and clusters tend to get more massive and achieve a more dynamically relaxed state as the Universe ages.
Galaxies falling into a massive galaxy group. Upon entering the group, these galaxies exhibit a blueshift in comparison to the central galaxy. Image Credit: Dr. LIAO Shihong
Satellite galaxy motions around these groupings and clusters reveal important information about their assembly state. Such motion observations provide important hints on the age of the Universe.
A study team led by Prof. Qi Guo from the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) examined the kinematics of satellite pairs orbiting big galaxy groupings using publicly available data from the Sloan Digital Sky Survey (SDSS). The results of the team’s investigation imply that the LCDM model with Planck cosmological parameters might have underestimated the age of the Universe.
Nature Astronomy published the findings on January 22nd, 2024.
The velocity offsets of satellite pairs from the core galaxy along the line of sight were used to study the motion of satellite pairs located on the other side of huge galaxy groupings. They found a significant overabundance of pairings with correlated velocity offsets as opposed to pairs with anti-correlated velocity offsets.
The excess of correlated satellite pairs suggests the presence of recently accreted or infalling satellite galaxies.
Qi Guo, Study Corresponding Author and Professor, National Astronomical Observatories, Chinese Academy of Sciences
This excess was also observed in recent cosmological simulations, although the size of the effect was far lower than in observations. The considerable difference between observations and simulations suggests that huge galaxy groupings are younger in the actual 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.
Dr. Qing Gu, Study First Author, Key Laboratory for Computational Astrophysics, National Astronomical Observatories, Chinese Academy of Sciences
These discoveries contradict the existing cosmological paradigm and may provide insight into the Hubble tension problem.
Journal Reference
Gu, Q., et. al. (2024) A younger Universe implied by satellite pair correlations from SDSS observations of massive galaxy groups. Nature Astronomy. doi:10.1038/s41550-023-02192-6