"Challenges of the age of the universe: Galactic dance reveals that the universe may be younger than thought

Motions of satellite galaxies around groups and clusters of giant galaxies could provide valuable insights into their evolution. The observations of such motion provide crucial clues about the age of the universe

A study using data from the "Sloan Digital Sky Survey" reveals that the universe may be younger than current estimates, and it challenges the accepted cosmological models, by analyzing the movements of satellite galaxies around giant galaxy groups.

In standard cosmological models, the process of formation of cosmological structures begins with the appearance of small structures, which then undergo mergers that depend on the size and mass of the structures, leading to the formation of larger systems. As the universe ages, giant galaxy groups and clusters, which constitute the largest systems, tend to increase in mass and reach a more dynamic state.

Motions of satellite galaxies around groups and clusters of giant galaxies could provide valuable insights into their evolution. The observations of such motion provide crucial clues about the age of the universe.

Using publicly available data from the Sloan Digital Sky Survey (SDSS), a research team led by Prof. Qi Guo of the National Astronomical Observatory of the Chinese Academy of Sciences (NAOC) analyzed the kinematics of satellite galaxy pairs orbiting giant galaxy clusters. . The team's findings suggest that the universe may be younger than predicted by the LCDM model with Planck's cosmological parameters.

The study was published in "Nature Astronomy" on January 22.

The researchers tracked the motion of pairs of satellite galaxies located on opposite sides of giant galaxy clusters by using their line-of-sight velocity differences from the central galaxy. They are the age of pairs showing correlated speed differences compared to pairs showing opposite speed differences.

"An excess of correlated satellite pairs indicates the presence of satellite galaxies that have recently merged or are currently merging," said Prof. Chi Guo, another author of the paper.

Such an excess is also found in recent cosmological simulations, but the magnitude of the effect was significantly lower than in observations. The significant discrepancy between the observations and the simulations suggests that massive galaxy clusters are younger in the real universe.

"Since the age of massive galaxy clusters can be closely related to the age of the universe, these findings indicate a younger universe compared to that derived from the cosmic microwave background (CMB) by the Planck partnership," said Dr. Qing Gu, first author. of the article.

These findings pose a challenge to the current cosmological model and may provide important insights into the Hubble constant. Hubble's law, or the Hubble-Lametre law, is a law in astrophysics and cosmology related to the expansion rate of the universe, according to the big bang theory. The value of Hubble's constant, as previously measured, is 67.11 kilometers per second per million persec. According to this, the age of the universe is calculated to be 13.819 billion years. The law is named after the astronomer Edwin Hubble, who in the late 20s discovered that the universe is expanding. He identified a redshift in the spectrum of distant galaxies, indicating that they are moving away from us. Hubble has collected data showing that the speed of a galaxy's receding is directly proportional to its distance from the Milky Way galaxy.

For the scientific article on the Nature website

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• Lost in Space: Is a Vast Void Dividing the Universe?
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