Infamous ‘WOW’ alien message ‘may have come from interstellar object 3I/ATLAS’
A recent natural hypothesis suggested a sudden brightening of hydrogen emissions from an interstellar cloud triggered by a magnetar flare
A leading astrophysicist has suggested that the famous “Wow! Signal” detected in 1977 may have originated from the interstellar object 3I/ATLAS, which passed near the same region of the sky just three days before the signal was recorded.
The claim comes from Professor Avi Loeb, head of the Galileo Project and founding director of Harvard University’s Black Hole Initiative. Writing in a new Medium article, Loeb argues that the alignment between the signal’s origin point and the object’s trajectory is too close to ignore.
The “Wow! Signal” was detected on August 15, 1977, as a powerful narrowband radio burst captured by Ohio State University’s Big Ear telescope. The source appeared extraterrestrial, and for decades astronomers have searched for an explanation.
A recent natural hypothesis suggested a sudden brightening of hydrogen emissions from an interstellar cloud triggered by a magnetar flare.
Loeb notes that on August 12, 1977, the interstellar object 3I/ATLAS was located about 600 astronomical units from Earth, equivalent to a light-travel time of three days.
At that moment, its sky coordinates were RA 19h40m (295 degrees) and Dec −19 degrees. The “Wow! Signal” originated from RA 19h25m (291 degrees) and Dec −27 degrees. Loeb calculates that the chance of two random sky positions being this closely aligned is roughly 0.6 per cent.
If the signal did originate from 3I/ATLAS, Loeb estimates that the transmitter would have needed a power output of 0.5 to 2 gigawatts, similar to the output of a terrestrial nuclear reactor.
The signal was detected at 1420.4556±0.005 MHz and appeared blue-shifted by about 10 km per second relative to the hydrogen line. Loeb notes that this is slightly smaller than the expected approach velocity of 3I/ATLAS, around 60 km per second.
“So far, no radio telescope reported data on 3I/ATLAS,” he writes, urging astronomers to examine whether the object emits any radio signals near the hydrogen hyperfine frequency.
Loeb also raises a broader question: how humanity should respond if an artificial signal is ever confirmed from an interstellar object.
He points to upcoming opportunities to study 3I/ATLAS. NASA’s Mars Reconnaissance Orbiter and ESA’s Mars Express and ExoMars missions will observe it between October 1 and 7, 2025, when it passes within 29 million kilometres of Mars. ESA’s Juice spacecraft will then observe it between November 2 and 25, 2025.
The professor notes that any required response would depend on how the object ranks on the “Loeb Scale”, a system he developed to assess potential threat levels.
Engagement options, he adds, could range from radio or laser messaging to sending interceptors for close-up examination.
Loeb concludes that humanity must be prepared for “a black swan event” involving interstellar objects that may appear benign yet pose unforeseen risks.
For the latest breaking news and stories from across the globe from the Daily Star, sign up for our newsletters .
