Has SETI Found an Alien Signal? Every Candidate So Far
Updated October 29, 2026
Short answer
No. As of October 29, 2026, no telescope has confirmed a signal, or any other trace, of extraterrestrial technology. Every candidate so far, from the 1977 Wow! signal to BLC1, China's FAST candidates and the interstellar comet 3I/ATLAS, was traced to human-made interference or to nature, or was never detected again.
Status: As of October 29, 2026: no confirmed alien signal. The newest candidate, a narrowband radio signal toward the star K2-155 found in data from China's FAST telescope, is most likely interference from Earth.
The Wow! signal (1977): unexplained, and never seen again
On August 15, 1977, Ohio State University's Big Ear radio telescope recorded a strong, narrow burst near 1420 MHz. That is the frequency at which hydrogen radiates, and SETI researchers (the search for extraterrestrial intelligence) had long guessed another civilization might use it. The signal lasted 72 seconds, exactly the time it took that patch of sky to drift through the telescope's beam. Astronomer Jerry Ehman circled it on the printout and wrote "Wow!" beside it.
Dozens of searches of the same area in Sagittarius have found nothing since. A signal that never repeats can't be checked, so it can't be confirmed. In 2024 a team led by Abel Méndez of the University of Puerto Rico at Arecibo proposed a natural cause: a cold hydrogen cloud that briefly brightened when a burst of radiation, for example from a magnetar, hit it. A 2025 follow-up refined its strength and position. It is a hypothesis, not a settled answer.
BLC1: the best candidate so far, and why it failed
In April and May 2019, the Breakthrough Listen project pointed the Parkes (Murriyang) radio telescope in Australia at Proxima Centauri, the nearest star to the Sun. An undergraduate intern, Shane Smith, later found a narrow signal at 982 MHz that seemed to appear only when the telescope pointed at the star. The story leaked to the press in December 2020.
Two papers in Nature Astronomy in October 2021 closed the case. Sofia Sheikh's team found about 60 lookalike signals in observations pointed at other parts of the sky. Their conclusion: human-made radio interference, probably from equipment on Earth's surface. It also produced a verification framework for future candidates.
Other famous "alien signals" and how they ended
The best-known false alarms:
- SHGb02+14a (2003): a SETI@home candidate from Arecibo data, near the hydrogen frequency. Its frequency drifted fast, and the project's own scientists called it unlikely to be real. It was never confirmed.
- Fast radio bursts (FRBs): millisecond flashes from distant galaxies. The first was reported in 2007, and thousands have been found since. In 2020 one came from a magnetar, a dead star with an enormous magnetic field, in our own galaxy. They are natural.
- Tabby's star (2015): irregular dips of up to 22% in a star's light prompted talk of an "alien megastructure." In 2018 observations showed the dimming depends on the color of light, which points to dust, not a solid structure.
- China's FAST telescope (2022): a state newspaper reported suspicious signals, then deleted the story. A scientist on the project said radio interference was very likely, and the team's paper concluded that its strongest candidate, toward the star Kepler-438, was most likely interference.
- K2-155 (2026): a new analysis of FAST's 2021 data found a narrow signal at 1148.4 MHz, only in the beam pointed at this red dwarf 238 light-years away. It was strong in only one polarization, and similar signals turned up near three other stars, so the authors consider interference from Earth more likely.
- Beta Pictoris b (2026): the first radio emission traced to a planet outside the solar system. It comes from auroras on a giant planet with an unusually strong magnetic field: nature, not technology.
Interstellar objects: 'Oumuamua, Borisov and 3I/ATLAS
'Oumuamua, discovered in October 2017, was the first object seen passing through the solar system from another star. It was elongated, showed no visible gas cloud, and sped up slightly as it left the Sun. Harvard astronomer Avi Loeb suggested in 2018 that it might be an artificial light sail. Most astronomers favor a natural explanation: a 2023 paper in Nature showed that hydrogen escaping from its ice could produce the push. Radio searches found nothing.
2I/Borisov (August 2019), found by amateur astronomer Gennady Borisov in Crimea, was plainly a comet. 3I/ATLAS, discovered on July 1, 2025 by the ATLAS survey telescope in Chile, is also a comet, according to NASA; it came no closer than about 270 million km to Earth and posed no threat. Loeb co-wrote a paper asking whether it could be alien technology, which its authors described as largely a pedagogical exercise. Searches with the SETI Institute's Allen Telescope Array, MeerKAT and the Green Bank Telescope found no artificial signals.
What about signs of life?
A biosignature is evidence of life itself, not of technology. In April 2025 a Cambridge-led team using the James Webb Space Telescope reported a tentative hint of dimethyl sulfide (DMS), a gas made on Earth mainly by marine life, on the planet K2-18b, 124 light-years away. The result fell short of the usual standard of statistical significance, later reanalyses found weaker evidence, and DMS can also form without life.
In September 2025 NASA announced a potential biosignature in a rock sample from Mars: something that may have been made by life but still needs more study. Neither is a confirmed discovery.
How a real detection would be checked and announced
A real signal would have to pass several tests. It must appear when the telescope points at the target and vanish when it points away. Its frequency drift must match a source moving with the sky, not with Earth. Above all, a second observatory with different equipment must detect it again. BLC1 failed that last test.
In June 2026 the International Academy of Astronautics (IAA) ratified an updated Declaration of Principles for SETI researchers, the first major revision since 2010. It says a candidate should be verified independently before any announcement; if it is confirmed, it should be reported promptly and fully to the public, the scientific community and the UN; and no reply should be sent before international consultations through a body such as the UN. These are voluntary scientific guidelines, not law. Researchers also grade claims on the Rio Scale, from 0 to 10, which weighs how credible a claim is against how big its consequences would be. More in our first contact protocol explainer.
How to read the next "alien signal" headline
A few questions sort out most claims:
- Who is claiming it? A paper or an observatory statement carries more weight than a social media post or a deleted article.
- Has a second telescope seen it? Without independent confirmation it is a candidate, not a detection.
- Does it repeat? A one-off blip can't be checked.
- Is it a natural phenomenon with an exciting name? Fast radio bursts, pulsars and planetary auroras all produce "signals from space."
- Even a confirmed signal would not mean anyone is coming: the nearest stars are light-years away (see the Fermi paradox). Follow updates on our live page.
Questions and answers
Has the Wow! signal been explained?
Not definitively. It has never been detected again. In 2024 researchers at the University of Puerto Rico proposed that a cold hydrogen cloud briefly brightened, a natural cause, but that is still a hypothesis.
Was BLC1 a signal from Proxima Centauri?
No. Two 2021 studies in Nature Astronomy concluded it was radio interference from human technology, most likely on Earth. Researchers found about 60 lookalike signals in observations pointed away from Proxima.
Did China's FAST telescope detect an alien signal?
No. The 2022 candidate was judged most likely interference, and the team that found the 2026 candidate toward the star K2-155 also considers interference from Earth the more likely source.
Is 3I/ATLAS an alien spacecraft?
There is no evidence that it is. NASA says 3I/ATLAS is a comet, and radio searches with several telescopes found no artificial signals. Avi Loeb's case for a technological origin is a minority view.
Has NASA found alien life?
No. NASA has reported a potential biosignature in a Mars rock sample, and a team using the Webb telescope reported a tentative hint of DMS on K2-18b. Neither is confirmed.
What happens if SETI detects a real alien signal?
Under the IAA guidelines updated in 2026, scientists would first ask independent observatories to confirm it, then announce it openly to the public, scientists and the UN. No reply would be sent without international consultation.
From the past hours
UFO news todaySources
- Méndez et al., Arecibo Wow! I: An Astrophysical Explanation for the Wow! Signal (arXiv, 2024)
- Sheikh et al., Analysis of the Breakthrough Listen signal of interest blc1 (Nature Astronomy, 2021)
- Li et al., A Wavelet-Integrated Search Pipeline for Narrowband Technosignatures in FAST Observations of 33 Exoplanet Systems (AJ, 2026)
- NASA: Comet 3I/ATLAS
- SETI Institute: Looking for signs of technology in interstellar visitor 3I/ATLAS
- Breakthrough Listen observations of interstellar object 3I/ATLAS
- Bergner & Seligman, Acceleration of 1I/ʻOumuamua from radiolytically produced H2 in H2O ice (Nature, 2023)
- Madhusudhan et al., New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI (2025)
- International Academy of Astronautics: updated SETI Declaration of Principles (press release, June 2026)
- Forgan et al., Rio 2.0: revising the Rio scale for SETI detections (International Journal of Astrobiology)
More explainers
- If aliens made contact tomorrow: the actual protocolThere's no binding first contact law. The real SETI protocol (updated 2026), who would speak for Earth, the UN's actual role, and whether we'd reply.
- Are aliens real? Yes, no, and what we actually knowAre aliens real? There's no proof. Life elsewhere is plausible, but no UFO has been shown to be alien. What science, NASA, AARO and the 2026 UFO files say.
- What happens if the US confirms aliens are real: the day-after guideIf the US confirmed aliens: who would announce it, what Congress and scientists would do, how people and religions react, and what wouldn't change.
- Is That UFO Video Real? How to Check It, Including AI FakesMost viral UFO clips turn out to be satellites, planets, launches, drones, balloons or AI fakes. Here is a 5-step check you can run in minutes.