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Interstellar visitor may be able to explain signal that came to Earth 48 years ago

David Benjamin
In 1977, a radio telescope detected a 72-second radio burst from space. The telescope was from Ohio State University’s Big Ear radio telescope, and it received an unusually strong narrowband radio signal. This led to a ripple of excitement in the scientific community about the possibility of having encountered evidence of life beyond Earth. At the time, astronomer Jerry Ehman spotted the burst, and annotated the major radio band fluctuation with the word ‘Wow!’ in red pen, – giving it a memorable nickname: the ‘Wow! Signal’. But now one astronomer thinks it comes from our interstellar visitor, the object 3I/ATLAS (Picture: Big Ear Radio Observatory and North American AstroPhysical Observatory (NAAPO)/Public domain, via Wikimedia Commons)
An image of the interstellar invader Comet 3I/ATLAS as seen by Hubble (Image credit: NASA/ ESA/Hubble)
The Wow signal has never been spotted again in the 48 years since. It has left plenty of questions, like where did it come from, and why did it last for 72 seconds. But Harvard astronomer Dr Avi Loeb has a wild new theory about the signal. In a new blog post, he suggested that interstellar object 3I/ATLAS could have been the source of the signal in 1977 – when it was still 600 times the distance between the Earth and Sun away from us (Picture: NASA/ ESA/Hubble)
Mandatory Credit: Photo by NASA/ESA/ZUMA Press Wire/Shutterstock (15433532a) Hubble captured this image of the interstellar comet 3I/ATLAS on July 21, 2025, when the comet was 277 million miles from Earth. Hubble shows that the comet has a teardrop-shaped cocoon of dust coming off its solid, icy nucleus. The Hubble Space Telescope has captured the best picture yet of a high-speed comet visiting our solar system from another star. Discovered last month by a telescope in Chile, the comet known as 3I-Atlas is only the third known interstellar object to pass our way and poses no threat to Earth. Hubble Telescope Captures Best Picture Yet Of A High-Speed Comet, In Space - 08 Aug 2025
Interstellar object 3I/ATLAS was first spotted on July 1 2025, by the Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope in Río Hurtado, Chile. It’s thought to be 20 kilometres wide and is travelling roughly 60km/s relative to the Sun. It is moving through the solar system at nearly twice the velocity of previous interstellar visitors ‘Oumuamua and Comet Borisov – and Nasa thinks it is a comet. Dr Loeb has also suggested the comet could be an interstellar probe sent by an intelligent species, who are on their way to scope out the Earth to see if there is any intelligent life in this solar system (Picture: NASA/ESA/ZUMA Press Wire/Shutterstock)
ESO?s Very Large Telescope (VLT) has obtained new images of 3I/ATLAS, an interstellar object discovered last week. Identified as a comet, 3I/ATLAS is only the third visitor from outside the Solar System ever found, after 1I/?Oumuamua and 2I/Borisov. Its highly eccentric hyperbolic orbit, unlike that of objects in the Solar System, gave away its interstellar origin.? This VLT image is the result of stacking several observations obtained on the night of 3 July 2025. When combining the different frames, the background stars were removed, showing only a deep image of the interstellar comet. The data were obtained with the FORS2 instrument, and are available in the ESO archive.? Links? Timelapse of the observations Single image with the entire sequence
Dr Loeb suggests that by examining the sky coordinates of the object and the Wow! Signal, the ‘chance of two random directions in the sky being aligned to that level is about 0.6 percent’. He wrote: ‘If the ‘Wow! Signal’ originated from 3I/ATLAS, how powerful was the transmitter?’. He theorises that 3I/ATLAS would have needed to have a power source of 0.5 to 2 gigawatts to send off the Wow! Signal from 600 astronomical units away, which he says is the equivalent to the ‘output of a typical nuclear reactor on Earth’ (Picture: ESO/O. Hainaut)
This image shows the observation of comet 3I/ATLAS when it was discovered on July 1, 2025. The NASA-funded ATLAS survey telescope in Chile first reported that the comet originated from interstellar space. ATLAS/University of Hawaii/NASA The NASA-funded ATLAS (Asteroid Terrestrial-impact Last Alert System) survey telescope in Rio Hurtado, Chile, first reported observations to the Minor Planet Center of comet 3I/ATLAS on July 1, 2025. Since the first report, observations made before the discovery were gathered from the archives of three different ATLAS telescopes around the world and Caltech’s Zwicky Transient Facility at the Palomar Observatory in San Diego County, California. These “pre-discovery” observations extend back to June 14.
But this theory would need a lot more additional data to confirm it. He added: ‘So far, no radio telescope reported data on 3I/ATLAS. Here’s hoping that the coincidence in the arrival direction of 3I/ATLAS and the ‘Wow! Signal’ would motivate radio observers to check whether 3I/ATLAS shows any radio transmission around the hyperfine line of hydrogen. To measure these properties, we should attempt to use all telescopes on Earth and in space’ (Picture:ATLAS/University of Hawaii/NASA)
This animation shows the observations of comet 3I/ATLAS when it was discovered on July 1, 2025. The NASA-funded ATLAS survey telescope in Chile first reported that the comet originated from interstellar space. Credit: ATLAS/University of Hawaii/NASA
The Wow Signal has attracted a number of strange theories. In one case, in 2017, a teacher from Florida suggested the signal came from a hydrogen cloud surrounding two comets that were near the location at the time. However, the clouds were not in view of the telescope and no such emission has ever been reported from a comet. Another theory in 2020 saw amateur astronomer Alberto Caballero use new data from ESA’s Gaia space observatory to search the location for sun-like stars. He came up with the star 2MASS 19281982-2640123 to have produced the signal as it has the same temperature, radius and luminosity as our own Sun  (Picture: ATLAS/University of Hawaii/NASA)

Will the 3I/ATLAS pose a danger to Earth? 

Nasa says 3I/ATLAS is a comet, and the European Space Agency says the comet will come no closer than 240 million kilometres – which is over 1.5 times the distance between Earth and the Sun. It says: ‘By the time the comet reaches its closest point to Earth, it will be hidden behind the Sun. It is expected to reappear by early December, offering astronomers another window for study’ (Picture: Hugo Mathy/ AFP)

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