What is sending radio signals to Earth from deep space like clockwork? Mysterious object 500million light years away is transmitting signals that hit our planet every 16-days without fail Astronomers have identified the first reliable pattern of a fast radio burst (FRB) source in deep space, but still don't know what causes the phenomenon. Such signals have baffled scientists since their discovery in 2014, as their origin is a complete mystery. But scientists have now found one sporadic radio burst source 500million light years away expressing a specific pattern. It belts out a signal for a few milliseconds once every hour, every hour for four days. It then goes silent for 12 days before resuming its 16 day cycle. This is the first time a FRB pattern has been spotted by astronomers but the underlying reasons are unknown. However, scientists have all but ruled out alien communication as 16 days for a message would be impractical and inefficient. The pattern was discovered after 400 days of observations by researchers at CHIME (Canadian Hydrogen Intensity Mapping Experiment). Some radio bursts detected on Earth are one-offs, coming from a random space and never seen again. 'This is very significant,' Duncan Lorimer, an astrophysicist at West Virginia University in Morgantown, told Science news. 'It's potentially going to take us in an interesting direction to get to the bottom of these repeaters.' No explanation has yet been found, but astronomers speculate it may be due to its source being in orbit. 'Such a periodicity, if confirmed, would be the first smoking-gun signature [of any particular property of an FRB source], which points towards very likely orbital motion,' Bing Zhang at the University of Nevada, Las Vegas, told New Scientist. It would mean two objects in orbit around one another would complete their journey every 16 days, with Earth receiving signals on the four days when the world is not blocked by its neighbour. But some repeat several times, although it was previously believed this was done at random. Now the astronomers at CHIME, who declined to comment on the finding, proved this not to be the case by studying FRB 180916. Scientists do not know if the repeating signal is an anomaly or the norm and have to contend with the possibility they have been looking for radio bursts in the wrong way for several years. .