If alien civilizations use hyper-efficient computers, they will have a distinct energy signal we can detect

A new paper claims that advanced alien civilizations might emit a distinct energy signal due to their use of hyper-efficient computers. The author suggests that such computers would operate at extremely low temperatures, generating waste heat in the far-infrared or submillimeter spectrum. The signal, called a Slysh halo, would be detectable from 100 light-years away. The paper argues that the most likely operating temperature for a Slysh halo is between 5 and 30 Kelvin, making it a potential technosignature. The key is that the heat would be faint but still detectable with advanced telescopes like ALMA. The article notes that the signal would be narrow and bright, unlike the debris halo around stars. The study is based on Landauer's principle, which states that the efficiency of computing is proportional to the operating temperature. The paper is available on arXiv (2026).

• The paper is titled "Slysh haloes: the waste heat of cold computing as a submillimetre technosignature" by Michael Garrett.
• The author argues that the most efficient computers would operate at temperatures between 5 and 30 Kelvin, emitting waste heat in the far-infrared or submillimeter spectrum.
• The Slysh halo would be detectable from 100 light-years away, and the heat would be emitted at a single narrow band.
• The article mentions that the signal would be faint but still detectable with advanced telescopes like ALMA.

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