In the image above, a faint trail of stars can be seen stretching across the galaxy. These structures, known as globular cluster stellar streams, are coherent stellar structures that retain a record of their dynamical history and can provide unique insights into the evolution of galaxies and the nature of dark matter.

Globular cluster stellar streams offer astronomers a unique opportunity to map otherwise invisible dark matter and study how it behaves. For many years, they have been difficult to observe because they are extremely faint. However, advances in large astronomical data sets and sophisticated analysis techniques have recently made stellar streams one of the most promising tools in galactic astronomy.

Now, Ph.D. student Julie Kiel Holm from the Niels Bohr Institute and associate professor Sarah Pearson from DTU Space, together with an international team of researchers, have made a discovery that has never been seen before. Their findings have just been published in Nature.