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)
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)
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)
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)
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)
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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