Breaking News:Radio Hunt Across 124 Light-Years Ends With a Striking Discovery– What Just Happened

A coordinated search using two major radio observatories has found no evidence of artificial radio transmissions from the exoplanet K2-18b. The campaign, which spanned frequencies from 544 MHz to 9.8 GHz, places new limits on the presence of powerful, persistent transmitters in the system 124 light-years away. The result narrows one specific avenue in the search for extraterrestrial intelligence, even as K2-18b remains a key target in studies of potentially habitable “Hycean” worlds.

K2-18b, a sub-Neptune exoplanet orbiting within the habitable zone of its host star, has drawn sustained attention since atmospheric observations suggested a hydrogen-rich environment consistent with a water-rich interior. In 2025, Nikku Madhusudhan and colleagues reported tentative signs of dimethyl sulphide (DMS) in the planet’s atmosphere, a molecule that on Earth is associated with life. Subsequent analyses, as reported by New Scientist, indicated that the spectral features could be explained by other molecules not linked to biology.

Against this backdrop of atmospheric debate, researchers turned to a different approach: searching for technosignatures, or signs of advanced technology. According to the new study posted on arXiv (DOI: 2602.09553), the team conducted a multi-epoch, interferometric search for narrowband radio signals that could indicate artificial transmitters operating within the K2-18 system.

A Coordinated Search across Two Continents

The observing campaign combined the Karl G. Jansky Very Large Array (VLA) in New Mexico, equipped with the COSMIC backend, and the MeerKAT radio telescope in South Africa using the BLUSE backend. Observations covered multiple frequency bands between 544 MHz and 9.8 GHz and spanned at least one full orbital period of K2-18b, which circles its star every 33 days.

At the VLA, data were collected in S-band (2.4–3.6 GHz), C-band (5–7.2 GHz), and X-band (8.1–9.8 GHz), with seven observing epochs in S-band and three each in C- and X-band. Each session observed the source for 10 minutes, split into 56-second segments that were independently processed.

MeerKAT conducted single-epoch observations in UHF (544–1015 MHz), L-band (900–1670 MHz), and S4-band (2625–3500 MHz). The BLUSE system formed 64 coherent beams across the field of view, enabling spatial discrimination between potential astrophysical signals and terrestrial interference.

According to the authors, the search targeted narrowband signals, typically less than 500 Hz wide, because such emissions are both characteristic of Earth’s own radio leakage and efficient as artificial beacons.

Filtering Interference and Testing Orbital Dynamics

To distinguish genuine extraterrestrial signals from radio frequency interference (RFI), the team applied a detailed post-processing framework. This included masking known RFI bands using observatory-provided databases, excluding signals with zero Doppler drift, and limiting detections to specific signal-to-noise ratios.

Signals were required to fall within calculated drift-rate ranges based on the expected orbital motion of K2-18b. The study estimates that 99% of plausible signals would drift at approximately 0.4 Hz per second between 544 and 1500 MHz, increasing to 4.177 Hz per second near 10 GHz.

The researchers also compared signals across multiple coherent beams. A genuine technosignature from K2-18b would be expected to appear only in the beam pointed at the planet’s position. Signals present in multiple beams at the same frequency and drift rate were treated as likely interference.

Across all bands and epochs, no signals consistent with an astrophysical or artificial origin were identified. As summarized in the paper, all surviving detections after filtering were attributable to terrestrial RFI or instrumental artifacts.

Upper Limits on Powerful Transmitters

The non-detections allow the team to set upper limits on isotropic, continuously emitting narrowband transmitters in the K2-18 system. According to the study, the sensitivity achieved implies that any such transmitter operating between 544 MHz and 9.8 GHz must have an equivalent isotropic radiated power below approximately 10^12 to 10^13 watts, depending on the observing band.

These limits are comparable to or below the effective power of the former Arecibo radio telescope, which was on the order of 10^13 watts. The constraints apply specifically to persistent, narrowband emitters illuminating Earth during the observing windows.

As Michael Garrett of the University of Manchester told New Scientist, “If there were a continuously transmitting, Arecibo-class beacon directed toward Earth [from K2-18b], they likely would have detected it.” He added that “a non-detection doesn’t tell us that the system is uninhabited. It simply constrains a very specific and possibly rare class of signals: persistent, relatively narrow-band radio transmitters operating in the observed frequency range and illuminating Earth during the observing windows.”