Astronomers listening out for signs alien life have received a mysterious radio signal originating from the general vicinity of Proxima Centauri – one of Earth’s closest neighbours.
And it has no obvious explanation raising the possibility the transmission is an alien signal.
Proxima Centauri is just 4.2 light-years away from Earth and is also the nearest star to the sun.
The signal was received amid 30 hours of observation in 2019 by astronomers at the Parkes Observatory in NSW.
It was then identified just a couple of months ago, as researchers trawled through the data, with its very narrow frequency of 982 MHz suggesting technological rather than natural origins.
The exciting discovery was only publicly revealed this week in news leaked to the British Guardian newspaper.
Proxima Centauri is also home to an Earth-like planet called Proxima b which is the nearest planet outside our solar system.
The signal was detected as part of the decade-long $US100 ($A131) million Breakthrough Listen project, founded in 2016.
The project is based at the University of California, Berkeley’s SETI Research Center, at the institution’s astronomy department.
Breakthrough Listen is funded by tech billionaire Yuri Milner and led by University of California, Berkeley astrophysicist Andrew Siemion.
“It has some particular properties that caused it to pass many of our checks, and we cannot yet explain it,” Siemion told Scientific American this week.
The signal has been named BLC1 or “Breakthrough Listen Candidate 1” and is being analysed for a paper for publication early next year.
“It’s the most exciting signal that we’ve found in the Breakthrough Listen project, because we haven’t had a signal jump through this many of our filters before,” Penn State University’s Sofia Sheikh told Scientific American.
Writing on the SETI website, the organisation’s senor astronomer Seth Shostak points out that Breakthrough Listen’s analysts will be looking at every possible explanation for the signal and canvasses many of them himself.
But he does allow some room for optimism.
“As long as we still don’t know, we should continue to consider the alien hypothesis viable,” Shostak writes.
“After all, any SETI detection is going to be dicey when we first make it … there will be plenty of calls for restraint intended to pacify the all-too-eager.
“But it’s reasonable to expect that someday one of these suspicious signals will, indeed, be the sought-after proof of intelligence on another world.”