A major SETI Institute investigation found no evidence of artificial narrowband radio signals coming from K2-18b, but the search significantly improved techniques for detecting possible extraterrestrial transmissions in the future.

Located 124 light-years away in the constellation Leo, K2-18b has become one of the most closely watched worlds in exoplanet science. The planet orbits within the habitable zone of a red dwarf star, where conditions could potentially allow liquid water to exist.

Figure 1. Scientists Scan K2-18b for Possible Alien Radio Signals

Observations from the James Webb Space Telescope suggest its atmosphere contains large amounts of carbon dioxide and methane, making it a strong candidate for a “Hycean” planet — a world with a hydrogen-rich atmosphere covering a vast global ocean.

Because of its potential habitability, researchers used two of the world’s most powerful radio telescopes to monitor the star system. According to a recent preprint published on arXiv, scientists analyzed millions of possible detections but found no convincing artificial radio signals from the planet at a technological level comparable to modern human civilization.

Two Powerful Telescopes Joined the Search for Alien Signals

The search relied on both the Karl G. Jansky Very Large Array and the MeerKAT, two of the most advanced radio telescopes on Earth. Coordinated observations between facilities of this scale are rare, making the campaign especially significant.

But the telescopes themselves were only part of the challenge. In radio astronomy, sophisticated software is equally critical because most detected radio signals originate from human activity on Earth rather than space. To handle this, researchers used advanced filtering systems designed to separate potential astronomical signals from massive amounts of terrestrial radio interference.

For the study, the VLA relied on the Commensal Open-Source Multi-Mode Interferometer Cluster system, while MeerKAT used the Breakthrough Listen User Supplied Equipment (BLUSE) platform. Both systems played a key role in identifying and filtering out Earth-based radio noise during the search for possible signals from K2-18b.

Scientists Had to Strip Away Earth’s Radio Noise

The filtering process still depended heavily on human decision-making, and the researchers applied five separate screening methods to identify possible alien technosignatures hidden within the data.

The first step involved removing radio frequencies heavily polluted by human-made interference on Earth, a process known as RFI masking. Any potential extraterrestrial signals broadcasting on those contaminated frequencies would likely remain undetectable from Earth-based observatories.

Scientists also filtered out signals that showed little or no Doppler shift — the same effect that changes the sound of a passing ambulance. Because signals traveling between planets should naturally shift in frequency due to motion, any signal without this change was assumed to originate from Earth and was discarded.

Researchers further excluded signals with extremely weak or unusually strong signal-to-noise ratios. This helped eliminate false positives and instrumental artifacts, though the team acknowledged it may also have removed some faint genuine signals.

Another important technique involved multibeam analysis. The telescopes created multiple focused beams across the sky, with one aimed directly at K2-18b and others pointed elsewhere. A true signal from the exoplanet would appear only in the targeted beam, while Earth-based interference would typically show up across multiple beams simultaneously.

The team also considered using transit filtering, a method that checks whether a signal disappears when the planet moves behind its star. However, because K2-18b did not pass behind its parent star during the observation period, that final filtering step was unnecessary.

No Alien Technosignals Survived the Final Screening

Despite detecting millions of possible signals during the observations, none survived the filtering process. Researchers found no confirmed narrowband radio technosignatures coming from K2-18b. While the result may seem disappointing, scientists say it still provides valuable scientific insight.

The search allowed researchers to establish “upper bounds” on the strength of any potential transmitter in the system [1]. In practical terms, if an extraterrestrial civilization exists there, it is not broadcasting signals stronger than something comparable to the former Arecibo Observatory radar facility.

Perhaps the most significant achievement was demonstrating the effectiveness of the automated filtering system itself. Manually sorting through millions of detected signals would have been nearly impossible. The new techniques could become essential for future observatories such as the Square Kilometre Array, which will collect vastly larger amounts of radio data. Scientists say that while K2-18b appears quiet for now, humanity’s ability to listen for possible extraterrestrial signals is rapidly improving.

Reference:

1. https://scitechdaily.com/are-there-aliens-on-the-famous-exoplanet-k2-18b-scientists-just-scanned-it-for-signals/

Cite this article:

Janani R (2026), Scientists Scan Famous Exoplanet K2-18b for Possible Signs of Alien Life, AnaTechMaz, pp.879.