Astronomers have solved a centuries-old puzzle surrounding one of the Universe’s oldest and densest star systems.
Globular clusters of stars were first discovered in the 17th century and scientists have long-debated how they formed.
Many stars in our own Milky Way and other galaxies are found in these tight clusters of several million stars.
Now a team of researchers, including astronomers from our Department of Physics, has used ultra-high resolution computer simulations to show how such clusters likely formed in the early Universe.
Their simulations traced the Universe’s 13.8-billion-year history in unprecedented detail.
They show that a fraction of stars in galaxies are born naturally in this tightly clustered way, leading to results like those seen through telescopes.
The research also unexpectedly revealed a new class of ancient star systems called globular-cluster-like dwarfs.
The simulated star clusters were seen to have a sizeable amount of dark matter – the mysterious substance that binds galaxies together – within them.
This new class resemble globular clusters, but due to the dark matter they are classified instead as small, or “dwarf”, galaxies.
We never expected these star clusters to emerge when we designed the simulations. Seeing them was a genuine surprise, and we’re now delving into their properties to see how they match up to the real deal seen through telescopes.
If found in the real Universe, such objects could become prime sites for the search for pristine, metal-free stars born in the early Universe.
They would also provide new locations to explore the nature of dark matter.
The findings are published in the journal Nature.
The research was led by the University of Surrey and co-authored by Professor Andrew Pontzen in our Institute for Computational Cosmology, Department of Physics.
Researchers used the UK’s DiRAC High Performance Computing Facility to run EDGE simulations over several years. The DiRAC facility made time available on a number of machines including COSMA, which is hosted and operated by Durham University.
Our Department of Physics is ranked 88th in the QS World University Rankings by Subject 2025. Visit our Physics webpages for more information on our undergraduate and postgraduate programmes.
Banner image: A globular cluster (white concentration of stars) naturally emerges in the high-resolution EDGE simulations. These simulations also predict the existence of a new class of object: globular-cluster-like dwarfs. These new objects form similarly to globular clusters but in their own dark matter halo. The nearby Reticulum II dwarf galaxy may be such an object that has been hiding in plain sight in our cosmic backyard. If so, it promises unprecedented constraints on the nature of dark matter and a new place to hunt for the first metal-free stars. Credit: University of Surrey, Matt Orkney, Andrew Pontzen and Ethan Taylor.
/prod01/prodbucket01/media/durham-university/research-/new-research-and-business/Research-and-Business-Partnerships.png)