Recent research suggests a strange radio signal that was once thought to be a sign of aliens in the closest star system to Earth, may be human technology. Turns out, not aliens.
On April 29, 2019, astronomers detected a signal emitted to Earth, from Proxima Centauri, the closest star system to our Sun (about 4.2 light-years away).
Proxima Centauri is also home to at least one potentially habitable planet. Because the signal fell into the 982 MHz radio waves rarely made by human planes or satellites, the researchers interpreted it as a possible sign of alien technology.
But the signal, which lasted for about five hours, never reappeared during subsequent Proxima Centauri scans. The reason, according to two new studies published Oct. 25 in the journal Nature Astronomy, may be that the signal didn't come from Proxima Centauri at all. To put it in Halloween-y terms: The call came from deep within the solar system.
"This is man-made radio interference from some technology, possibly at the Earth's surface," said Sofia Sheikh, an astronomer at the University of California, Berkeley, and co-author of both papers.
Astronomers captured five hours of radio waves with the Parkes Murriyang radio telescope in southeastern Australia during the 26-hour Proxima Centauri survey. The survey is part of a $100 million alien-hunting program called Breakthrough Listen, which uses telescopes around the world to capture possible extraterrestrial transmissions.
The telescope recorded more than 4 million radio signals from around Proxima Centauri during that observation, but only BLC1 astronomers found unusual, both for its long duration and odd wavelength. The team quickly ruled it out for possible interference by satellites or other man-made aircraft.
However, after the signal failed to reappear in subsequent stellar observations, the researchers reviewed their initial data. This time, they discovered that their previous automatic sorting system ignored some signals that looked very similar to BLC1 but were transmitted at different frequencies.
In the second of two new Nature papers, the researchers conclude that BLC1 and the "similar" signal are components of the same radio source, and that the radio source is likely something on Earth's surface, somewhere within a few hundred miles of the telescope. Parkes Murriyang. The team said the signal could have emerged during the five-hour observation of Proxima Centauri perhaps by chance.
"Since the signal never reappeared, it is possible that it came from a malfunctioning electronic equipment that was either turned off or being repaired," Sheikh said.
The researchers say the frequency range in the signal is also consistent with the frequency of the common clock oscillators used in digital electronics. This suggests a nearby phone or computer on the fritz may have generated what is considered an 'alien signal'. Currently, the team is planning further studies to find out what the source is.