For centuries, astronomers have puzzled over the origins of one of the universe’s oldest and densest stellar systems, known as globular clusters. Now, a university of Surrey-led study published in Nature has finally solved the mystery using detailed simulations – while also uncovering a new class of object that could already be in our own galaxy.

Globular clusters are dense collections of hundreds of thousands to millions of stars found orbiting around galaxies, including the Milky Way. Unlike galaxies, they show no evidence of dark matter, and their stars are unusually uniform in age and chemical composition – traits that have left scientists debating their formation since their discovery in the 17th century. According to the Space.com, there are approximately 150 known globular clusters in the Milky Way.

Surrey researchers used ultra-high-resolution simulations that can trace the Universe’s 13.8-billion-year history in unprecedented detail, allowing them to watch globular clusters form in real-time within their virtual cosmos, called EDGE. The simulations find multiple pathways for their creation and, unexpectedly, the emergence of a new class of star system – “globular cluster-like dwarfs” – that sits between globular clusters and dwarf galaxies in terms of their properties.

Dr. Ethan Taylor, Postdoctoral Research Associate at the University of Surrey’s School of Mathematics and physics, explained that clusters can form in at least two different ways, both without dark matter. This finding challenges previous assumptions about the necessity of dark matter in the formation of these structures.

The next step is to confirm the existence of these globular cluster-like dwarfs through targeted observations with telescopes, including the James Webb Space Telescope and upcoming deep spectroscopic surveys. If they do, it could give astronomers new ways to test dark matter theories and offer some of the best chances to find the Universe’s very first generation of “metal-free” stars.

Understanding Globular Clusters and Dwarf Galaxies

Globular clusters and dwarf galaxies represent distinct endpoints in stellar system evolution. Globular clusters are tightly bound, ancient collections of stars, while dwarf galaxies are smaller, less dense galaxies with more complex structures. The newly discovered “globular cluster-like dwarfs” blur the lines between these two categories.