There are roughly four malicious extraterrestrial civilisations in the Milky Way that could attack our planet, a researcher has claimed.

As per Vice, Alberto Caballero, a PhD student at the University of Vigo in Spain, has said that he pinpointed the exact source of the “WoW Signal”, which was detected in 1977 and was a strange minute-long burst of radio energy. 

Mr Caballero explained that the Big Ear telescope at Ohio State University received a burst of radio waves that lasted a minute and 12 seconds. The signal contained an alphanumeric code and it was dubbed the “WoW Signal”. It is considered the best candidate signal of extraterrestrial life since humans began searching more than 60 years ago. 

Over decades, researchers tried to study the signal and its origins in further detail. Now, in his paper - titled “Estimating the Prevalence of Malicious Extraterrestrial Civilizations”- Mr Caballero claimed that he had pinpointed the exact source of this signal. He believes that it originated from a Sun-like star 1,800 lightyears from the Earth. 

Mr Caballero's research is considered to be more of a “thought experiment”. The researcher said that the aim of his paper is to warn other scientists and put a number to the civilizations that could possibly revert to the messages we send out. 

In putting together his study, Mr Caballero counted the number of invasions that have happened on Earth - including the Wow Signal - and then applied this to the estimated number of exoplanets in the Milky Way. By his calculations, the number of civilisations that could possibly invade our planet is four. He warned scientists to use caution in using the practice of Messaging Extraterrestrial Intelligence (METI) for fear it could provoke an alien invasion. 

However, as per New York Post, the researcher also concluded that the odds of extraterrestrials wiping out the human species is about the same as the Earth being hit by a “planet-killer asteroid”. In his paper, Mr Caballero wrote that such an event takes place once every 100 million years, so humans are in all likelihood safe for the time being. 

He also stated that there is likely fewer than one malicious extraterrestrial civilisation in the Milky Way that has also mastered interstellar travel. Further, the researcher said that as societies advance, they are less likely to engage in conflict, suggesting to him that an alien force will also follow the same behaviour as they progress technologically. 

Mr Caballero hopes that his research will help start a conversation about whether it is actually risky to send messages into space. His research comes amid a time when the US government has taken seriously increasing signs of extraterrestrial life, though there is still no definitive proof.