Stars are generally very “social” creatures. They can often be found in full-fledged galaxies like our Milky Way or in much smaller star clusters, bound together by gravity. But scattered throughout the universe are rogue stars, not gravitationally bound to others, wandering forever in the endless cosmos. While the light from these stars, known as intracluster light, was first detected by Fritz Zwicky in 1951, a new infrared study by the Hubble Space Telescope has shed light on this faint glow and research, if you’ll excuse the wordplay. It could help scientists unravel the mystery of the origin of these rebellious stars.

During the study, 10 galactic clusters or groups of gravitationally bound galaxies, located 10 billion light-years away, were studied. What the researchers found in the data is that the ratio of in-cluster light to total cluster light is constant. This suggests that wandering stars are old – billions of years old – and unlikely to have sprung out of galactic clusters they formed in a recent explosion (when enormous gravitational fluxes pull material from galaxies). If stripping were the main source of stray stars, scientists would expect the fraction of light within the cluster to increase over time compared to the light of galaxy clusters.

“We don’t know exactly what makes them homeless. Existing theories cannot explain our results, but somehow they were retained in large quantities in the early universe,” said astronomer James Gee of Yonsei University in South Korea and co-author of the study. “In the early years of their formation, galaxies can be quite small and become stars quite easily due to the weaker gravity.”

The James Webb Space Telescope joins the fun as Hubble continues to probe the universe for in-cluster light. Together we hope that the powerful observatories will help scientists unravel the mystery of the birth of wandering stars. And perhaps an even bigger mystery, because these strange stars could give scientists insight into dark matter, the invisible matter that makes up most of the matter in the universe and whose gravitational force holds galaxies together.

Co-author Hyungjin Joo said, “If we find the origin of the stars within the cluster, it will help us understand the merger history of the entire galaxy cluster, and they can serve as visible traces of the dark matter surrounding the cluster.” He also made the same statements from Yonsei University.