Astronomers have proposed a new type of technosignature — a hypothetical trace of activity by an extraterrestrial civilization. The idea is that an engineered system could extract a star's rotational angular momentum and use it as an energy source.
The authors named the effect Stellar J-Harvesting. Unlike a classical Dyson sphere, such a construction need not produce an excess of mid-infrared radiation. Its main marker is different: the star would rotate noticeably slower than similar neighbours.
The researchers derived a relation between energy and rotation period and applied a slow-rotator search to stars from the Kepler mission. Stars were sorted by colour and surface gravity, then run through eight filters against false positives. The clean sample left 6,725 main-sequence stars of classes F, G and K.
Two candidates turned up with deviations above 4 sigma. But Gaia DR3 data and WISE telescope images point to more ordinary explanations: unresolved binary systems and low metallicity. So there is no detection claim. Instead the authors set a cautious upper limit on the occurrence of such signals: fewer than 4.5 per 10,000 stars.
The main result is not the candidates but the method itself. It shows that technosignatures tied to stellar rotation can be tested with existing catalogues. And the strongest outliers become concrete targets for spectroscopy, imaging and radio observations.