SETI shifts to high‑frequency ALMA data and long‑pulse beacons

A new pre‑print paper by Dániel Apai, Chia‑Lung Lin and Kevin Wagner argues that an extraterrestrial civilization seeking inexpensive interstellar communication would favor long‑duration laser pulses (micro‑ to milli‑second) placed in interstellar orbit rather than costly femtosecond bursts aimed at a host star. The authors contend that such “lighthouse” beacons would be more detectable because they avoid stellar interference.

At the same time, astronomer Louisa Mason (University of Manchester) presented a practical SETI survey that repurposes archived observations from the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. By analysing Band 3 data at 90.642 GHz and 93.151 GHz – frequencies largely ignored by traditional SETI – Mason searched for narrow‑band spikes that could signal technosignatures. The method leverages “stellar bycatch,” extracting signals from stars recorded incidentally during unrelated ALMA observations, dramatically expanding the number of stars examined without new telescope time. Both efforts aim to broaden the search beyond the classic “water hole” (1.42–1.66 GHz) into higher‑frequency radio bands, opening new parameter space for the detection of possible alien technosignatures.