Euclid telescope finds brightness gap of missing red dwarf stars in globular cluster NGC 6397
The Euclid space telescope spotted something astronomers were not hunting for: a thin band of missing red dwarf stars inside NGC 6397, one of the closest ancient star clusters to Earth. The same brightness gap had only been seen in scattered nearby stars, never inside a globular
A survey by the European Space Agency's Euclid telescope has turned up a feature that nobody set out to find. While studying NGC 6397, one of the closest ancient globular clusters to Earth, scientists at the Space Telescope Science Institute sorted the cluster's stars by brightness and color. What appeared was a thin gap: a narrow band where a population of low-mass red dwarf stars should sit, but is missing. The same brightness gap had been spotted before, in scattered nearby stars observed by the Gaia mission. It had never been seen inside the dense, crowded environment of a globular cluster, where hundreds of thousands of stars are packed together. Researchers believe the gap is linked to a structural change that happens deep inside stars at one specific mass, briefly altering how brightly they shine. The discovery was accidental. It emerged only when large sky-survey datasets were cross-checked against each other, a reminder of how much sits unnoticed inside data that telescopes have already collected. The results were published in Astronomy and Astrophysics.