Newshot Suspected "artificial feature" signal found in China's FAST data; paper authors lean toward interference rather than alien civilization
IT之家 November 12 news: Today, an analysis result based on historical data from China's FAST telescope has drawn attention.
A team led by Chinese scientists, while scanning 33 exoplanetary systems, identified a narrow-band radio signal with "artificial features" coming from the direction of the K2-155 red dwarf system about 238 light-years away, designated NBS 260108.
The related paper has been published in The Astronomical Journal, with Zi-Qi Li of Beijing Normal University as the first author.
NBS 260108 was singled out because it simultaneously possesses two features that attract much attention in SETI (search for extraterrestrial intelligence) research. The first is an extremely narrow frequency band.
When searching for alien technological signals, scientists usually focus on narrow-band signals, because radiation from natural celestial bodies is mostly broadband, while narrow-band signals are more likely to come from artificial equipment. This signal appeared only in the beam pointing at K2-155, was not detected in any other beam, and its frequency changed steadily over time, consistent with "artificial features."
The researchers wrote in the paper: "Natural astrophysical processes rarely produce extremely narrow spectral features, whereas artificial transmitters often do."
Radiation from natural radio sources usually covers a wide frequency range, while signals produced by technological civilizations can be highly concentrated near a single frequency. The second feature is frequency drift over time. Due to the relative motion caused by a planet's rotation and revolution, the signal frequency of a distant transmitter undergoes regular shifts, appearing as a slanted track on a frequency-time plot.
IT之家 note: This phenomenon is the Doppler effect; the received frequency depends on the relative speed and direction between the transmitter and the observer, and the slope of the drift can reflect the kinematic characteristics of the transmitter.
K2-155, toward which the signal points, is a red dwarf known to host three "super-Earths." The outermost of these, K2-155d, lies at the edge of the star's habitable zone, has a radius about 1.64 times that of Earth, and an orbital period of about 40.7 days, and theoretically has the conditions for liquid water on its surface.
The research team said it is precisely the presence of this habitable-zone super-Earth that makes K2-155 "an intriguing SETI target."
Although the signal's features invite speculation, both the research team and the paper itself remain highly restrained about the conclusion. The paper explicitly states: "The generation of a candidate signal and the interpretation of a candidate signal should be kept separate."
Further inspection found that NBS 260108 appears strongly in only one polarization channel, and that similar features also appeared in observations pointing at three other stars. After considering polarization asymmetry, off-beam recurrence, and other interference structures in the same band, the paper concludes that human-made or instrumental interference is a more reasonable explanation than a transmission from an extraterrestrial civilization. The authors accordingly classify NBS 260108 as "a low-priority technosignature candidate rather than a robust detection."
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