Using data from the European Space Agency's Gaia mission, Richard I. Anderson of EPFL and Emily Hunt of the Max Planck Institute for Astronomy produced the first galaxy-scale map linking variable stars to their host open clusters, tallying nearly 35,000 variables in 1,200 clusters. The study appears as a Letter in Astronomy and Astrophysics.
Open clusters serve as natural laboratories beca by Robert Schreiber
Berlin, Germany (SPX) Aug 15, 2025
Using data from the European Space Agency's Gaia mission, Richard I. Anderson of EPFL and Emily Hunt of the Max Planck Institute for Astronomy produced the first galaxy-scale map linking variable stars to their host open clusters, tallying nearly 35,000 variables in 1,200 clusters. The study appears as a Letter in Astronomy and Astrophysics.
Open clusters serve as natural laboratories because their stars form together and share distance and age, while variable stars reveal interior physics through brightness changes. Combining both populations in one analysis exposes how stars live in communities and evolve across the Milky Way.
"It is a scientific first in the way that large samples of star clusters and variable stars are analyzed together," said Anderson.
The team drew on Gaia's third data release and limited the sample to clusters within about 6,500 light years to ensure reliability. They cross matched Gaia's variable-star catalog with cluster memberships, then assessed each star's age, distance, and brightness within its cluster context.
Results indicate that at least one in five cluster stars varies in brightness. Younger clusters host the widest mix of variability types, whereas older clusters are dominated by stars with slow, Sun-like cycles. Specific variable classes also act as age markers, simplifying cluster dating without intricate models.
The authors released a public catalog listing positions, types, and properties for the 35,000 variables, and assembled a particularly clean Hertzsprung Russell diagram charting where each variability class appears. The catalog offers a foundation for testing stellar evolution scenarios across many environments.
Although the spacecraft was recently turned off, Gaia now enters its most productive scientific phase as Europe processes its vast archive spanning nearly 2 billion stars. Successive data releases will enable broader and more precise variability studies across the Galaxy.
"Our work is a teaser for what is to come with Gaia [data releases 4 and 5], which will revolutionize the study of stellar populations by their light variations," said Anderson.
"We are made of stardust," said Anderson. "Understanding the lives of stars and the physics that govern stars is crucial to understanding our origins and place in the cosmos."
Research Report:A bird's eye view of stellar evolution through populations of variable stars in Galactic open clusters
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