Astronomers at the W.M. Keck Observatory have made a groundbreaking discovery that challenges our current understanding of galaxy formation in the universe. A new ultra-diffuse galaxy, FCC 224, has been found to be devoid of dark matter, which is a fundamental component assumed to be necessary for galaxies to form.
Located approximately 60-65 million light-years from Earth, FCC 224 is situated on the outskirts of the Fornax Cluster. This unusual galaxy features an unexplained globular star cluster system, with many more luminous clusters than expected and no dark matter detected within its inner regions.
Researchers led by Maria Luísa Buzzo and Yimeng Tang analyzed FCC 224 using high-resolution spectroscopy from Keck Observatory’s Keck Cosmic Web Imager (KCWI). Their study found that the galaxy’s star clusters are similar to those of other dark matter-deficient galaxies, suggesting a possible link between these features and the absence of dark matter.
The discovery challenges conventional models of galaxy formation, which rely on dark matter. The researchers suggest that an external interaction, such as a high-velocity collision, may have separated the galaxy’s dark and visible matter, forming the “bullet-dwarf model.” However, additional data is needed to test this theory.
This finding raises fundamental questions about the necessity of dark matter in shaping galaxies. As observational capabilities improve, astronomers aim to conduct larger surveys to identify similar galaxies and investigate their origins. The discovery of FCC 224 provides a crucial data point in understanding these rare galaxies and refining our comprehension of dark matter’s role in dwarf galaxy formation.
Source: https://phys.org/news/2025-04-evidence-dark-free-dwarf-galaxy.html