Space & Astronomy

Scientists Scanned Exoplanet K2-18b for Alien Signals — Here Is What They Found

Two of the most powerful radio observatories on Earth pointed at the same distant world for weeks, searching for any hint of intelligent technology. The result reveals as much about the future of SETI as it does about one intriguing exoplanet.

• K2-18b is a Hycean world — a planet with a hydrogen-rich atmosphere and a global liquid-water ocean — located 124 light-years from Earth in the constellation Leo. It orbits within the habitable zone of its red dwarf star, making it one of the most promising known candidates for hosting extraterrestrial life.
• A team led by researchers from the SETI Institute used the Karl G. Jansky Very Large Array (VLA) in New Mexico and the MeerKAT radio telescope in South Africa to conduct the most sensitive narrowband technosignature search ever performed on the system. The campaign scanned millions of frequency channels for artificial radio signals.
• No confirmed technosignatures were detected. The search ruled out the presence of any civilization broadcasting omnidirectional radio signals at power levels above roughly 10 megawatts — a threshold that Earth itself exceeded only a few decades ago with its most powerful Cold War radars.

The search for extraterrestrial intelligence has always faced a fundamental asymmetry: the Universe is vast, and we have only begun to listen. K2-18b became a primary target after the James Webb Space Telescope detected carbon-bearing molecules — including methane and carbon dioxide — in its atmosphere in 2023, observations that some scientists noted were consistent with biological activity. While non-biological explanations remain equally plausible, the planet's proximity and potential habitability made it an irresistible target for radio SETI.

Over the course of several weeks, the team collected petabytes of raw radio data and processed them through a specialized pipeline designed to filter out terrestrial interference — the constant buzz of Earth's own communication signals. Millions of initial candidate detections were winnowed down by removing signals that originated from human technology, appeared only briefly, or exhibited Doppler shifts inconsistent with a source on or near K2-18b. After the filtering process, zero artificial signals remained.

The null result is not discouraging. It represents a step forward in technical capability. The combination of VLA and MeerKAT allowed researchers to cover a wider frequency range at higher sensitivity than any previous SETI campaign focused on a single exoplanet. Future searches with the Square Kilometre Array, expected to come online later this decade, will be able to detect signals thousands of times fainter than the current threshold. As the team noted, the silence of K2-18b only narrows the search space — it does not close the question.