An international research team led by the University of Toronto has announced the discovery of the darkest dark galaxy known to date, designated as CDG-2, located approximately 245 million light-years away. According to current cosmological models, dark matter constitutes about 27% of the total energy density of the universe and around 85% of its total mass, with preliminary indications suggesting that this specific galaxy may consist of over 99.9% dark matter. The research highlights the unique challenges of detecting such galaxies, which are often dim and sparse in stars, making them exceedingly difficult to observe.

The team utilized the Hubble Space Telescope along with additional observational tools like the Euclid Space Telescope and the Subaru Telescope to identify CDG-2 in the Perseus Cluster. Their methods involved examining low surface brightness galaxies and dark galaxy candidates in squarish star clusters, which are defined by the gravitational binding of stars in spherical formations. The presence of tightly bound star clusters in rapid rotation is a pivotal clue indicating the potential existence of a massive, invisible gravitational body — a dark galaxy.

Upon closer inspection, the researchers discovered a faintly diffused ring of light surrounding these star clusters, which serves as further evidence of the underlying dark galaxy's presence. This marks a notable achievement in astronomical research, as it is the first time a dark galaxy has been identified based solely on observed star clusters. The findings were published in the journal The Astrophysical Journal, underscoring the significance of this discovery in the ongoing quest to understand the nature and distribution of dark matter in the universe.