A new study proposes that advanced extraterrestrial civilizations might reveal themselves not through radio messages or infrared waste heat, but by changing the rotation of their host stars. The concept, called Stellar J-Harvesting, describes an engineered system that extracts a star’s rotational angular momentum. Unlike a Dyson sphere, such technology would not need to block a large fraction of the star’s light and might produce too little waste heat to appear in existing infrared surveys. Its most visible effect could instead be a star rotating much more slowly than comparable stars of similar colour and evolutionary state.

To test the idea, the researcher analysed rotation measurements and stellar properties from Kepler and Gaia-based catalogues. After applying eight filters designed to remove natural slow rotators, including subgiants, metal-poor stars and binary systems, the final sample contained 6,725 FGK main-sequence stars. Two stars stood out at more than four standard deviations from their comparison groups, with rotation periods of approximately 61 and 65 days rather than the expected 5–10 days.

However, the study does not claim the discovery of alien technology. Gaia and WISE observations indicate that unresolved companions, low metallicity or other ordinary astrophysical effects could explain the anomalies. The two objects therefore remain follow-up targets rather than technosignature detections. The pilot survey places an upper limit of fewer than 4.5 strong J-Harvesting systems per 10,000 comparable stars.

For SETI, the study is important because it expands the search beyond conventional radio transmissions and Dyson-sphere waste heat. It introduces stellar rotation as a measurable technosignature and provides a practical framework for identifying unusual stars using existing catalogues. Future spectroscopy, high-resolution imaging and radio observations could help distinguish artificial spin-down from natural stellar evolution.

For more details, read the original paper.