Summary
A team conducted one of the broadest and most sensitive technosignature searches ever on the K2-18 planetary system using the Very Large Array (VLA) in New Mexico and the MeerKAT radio telescope in South Africa, observing for 33 days (one K2-18b year) across 544 MHz to 9.8 GHz. After filtering 20+ million candidate signals from VLA alone, they found no radio emissions consistent with a technological origin. The result stands in notable tension with the earlier jwst-based biosignature claim on the same planet reported in src-jwst-k2-18b-biosignature-2025 — the same target now carries both a potential atmospheric biosignature (disputed) and a radio-technosignature null. Authors emphasize the methodology framework as the more durable contribution, portable to any hycean world candidate as the SKA and ngVLA come online. Accepted by The Astrophysical Journal.
Key Claims
- VLA observed K2-18 Sept 29 – Dec 21, 2023; MeerKAT observed late Sept / early Oct 2023; combined coverage spans one full 33-day orbit
- Frequency range 544 MHz – 9.8 GHz is significantly broader than prior K2-18b technosignature searches, with sensitivity to transmitters ~1,000x weaker
- After multi-beam directionality filtering, MeerKAT eliminated all remaining candidates; VLA retained ~14,600 for further filtering
- Additional filters: Doppler-drift-rate matching to K2-18b’s motion, rejection of zero-drift (terrestrial) signals, occultation check (signal must disappear behind host star), temporal-evolution check, and visual inspection
- Null result consistent with: an uninhabited planet, pre-technological life, or technological civilizations using non-radio, broadband, low-duty-cycle, or encrypted signals
- The paper itself describes the DMS/DMDS biosignature interpretation as “heavily disputed”
- k2-18b remains a leading habitability candidate: sub-Neptune, 124 light-years away, in the habitable zone of red dwarf K2-18
- Grounded in the 1959 Cocconi & Morrison paper on narrowband radio beacons that launched modern seti
Notable Quotes
“This result is consistent with several possibilities: K2-18 b may be uninhabited, it may host pre-technological life, or any technologically capable civilization may employ communication modalities that are not detectable with our current observing strategy (e.g., non-radio, broadband, low-duty cycle, or highly encrypted signals).” — study paper
“K2-18 b may not have answered the question of whether we’re alone, but it is helping scientists figure out how to ask it better.” — Brooks Mendenhall