SETI Scans K2-18b, Finds No Aliens
VLA and MeerKAT telescopes targeted K2-18b, a habitable zone world 124 light-years away with JWST-detected CO2 and methane. After processing millions of signals through 5-stage filters, researchers found no technosignatures stronger than Arecibo — but validated an AI pipeline for the Square Kilometre Array.
The search for technosignatures on K2-18b was a coordinated effort using the Karl G. Jansky Very Large Array (VLA) in New Mexico and the MeerKAT telescope in South Africa. Observations spanned multiple epochs to cover at least one full 33-day orbit of the planet and covered a wide frequency range from 544MHz to 9.8GHz. K2-18b was prioritized for this search after JWST observations detected carbon-bearing molecules like methane and carbon dioxide in its atmosphere. These findings are consistent with predictions for a "Hycean" planet—a theoretical ocean-covered world with a hydrogen-rich atmosphere, making it a compelling target in the search for habitable worlds. The planet, discovered in 2015 by the Kepler space telescope, is about 8.6 times the mass of Earth and 2.6 times its radius. It orbits a red dwarf star 124 light-years away in the constellation Leo, residing within the star's habitable zone where liquid water could potentially exist. Further JWST observations have also hinted at the controversial presence of dimethyl sulfide (DMS), a molecule that on Earth is predominantly produced by life, primarily marine phytoplankton. This unconfirmed finding has generated significant debate among scientists, with some urging caution due to the possibility of false positives or unknown abiotic chemical processes. The non-detection of signals from K2-18b sets an upper limit on the power of any potential transmitters, indicating there are no persistent, isotropic narrowband transmitters stronger than the planetary radar of the former Arecibo Observatory. This provides the first-ever interferometric technosignature constraints for a Hycean planet candidate. The sophisticated data-filtering pipeline, enhanced by AI, successfully sifted through millions of potential signals, weeding out terrestrial interference. This methodology serves as a crucial testbed for future, more sensitive searches that will be conducted with next-generation instruments like the Square Kilometre Array (SKA). The upcoming Square Kilometre Array will be up to 100 times more sensitive than current radio telescopes. It will be capable of detecting leakage radiation, equivalent to our own television transmitters, from planets orbiting the nearest stars, dramatically expanding the search for extraterrestrial intelligence.
