Euclid Telescope Finds Missing Red Dwarfs in Ancient Star Cluster

Scientists from the Space Telescope Science Institute (STScI) discovered a brightness gap in the ancient globular cluster NGC 6397 [1, 2, 3].

This finding suggests a missing population of red dwarf stars, which could force astronomers to rethink how these small stars evolve over billions of years. Because globular clusters are some of the oldest structures in the universe, they serve as critical laboratories for studying the life cycles of stars.

The research team based in Baltimore, Maryland, used observations from the Euclid space telescope to analyze the cluster [1, 4, 5]. The telescope revealed an unexpected void in the distribution of stellar brightness, a gap where a specific cohort of red dwarfs should have been present [2, 3, 4].

Researchers said the discovery was not the primary goal of the observation. They said they were not looking for the gap but found it during their analysis of the data ^[3]. The results were published June 5, 2026, in the journal Astronomy & Astrophysics [2, 4].

Red dwarfs are the most common type of star in the Milky Way, yet they remain difficult to study in ancient clusters due to their low luminosity. The identified gap in NGC 6397 indicates that these stars may be disappearing or evolving differently than current models predict [1, 4].

STScI astronomers said the study provides new insight into the overall stellar structure of the Milky Way's globular clusters [2, 4]. By investigating why these stars are missing, scientists hope to refine the timeline of stellar decay, and the chemical composition of early galactic environments [1, 4].