In the search for extraterrestrial intelligence, astronomers have come across a variety of unusual phenomena in the universe; while natural explanations have been found for them, so far at least, some of these phenomena can be very bizarre. Fast Radio Bursts (FRBs) are one such example, and one for which an explanation has not yet been found—very brief (milliseconds), but powerful radio emissions from outside of our galaxy. Now, a new detection of 15 repeating radio bursts has been made by astronomers, adding a new piece to the puzzle and posing more questions.
The new bursts were detected by Breakthrough Listen, a project to search for possible evidence of alien signals, radio or otherwise, on Aug. 26, 2017. They were found using the Breakthrough Listen backend instrument at the Green Bank Telescope in West Virginia. 400 TB of data were obtained over a five-hour period, observing the entire 4 to 8 GHz frequency band.
The 15 new bursts all originate from the same FRB, called 121102. It is the first, and so far only, FRB known to repeat, making it of special interest. FRB 121102 was discovered on Nov. 2, 2012, and found to repeat in 2015. In 2016, its specific location was determined to be a dwarf galaxy about 3 billion light-years away from Earth.
These new bursts were also found to be emitting at higher frequencies than ever previously observed, up to 7 GHz.
“Bursts from this source have never been seen at this high a frequency,” said Andrew Siemion, director of the Berkeley SETI Research Center and the Breakthrough Listen program.
The results were posted in the Astronomer's Telegram on Aug. 29, 2017.
The causes of FRBs are as yet unknown, but theories include rotating neutron stars with strong magnetic fields. A more speculative possibility is that they are the product of alien intelligence, perhaps to serve as "navigation guides" or directed-energy beams to propel solar-sail type spacecraft.
As Seth Shostak, a senior astronomer at the California-based SETI Institute, told GeekWire, FRB 121102 is the “one burster that it pays to observe,” since it’s the only one so far that’s been known to repeat.
Of course, any detection of odd radio signals from space brings up the big question—could they be from alien intelligence? Nature can produce many types of radio emissions, such as from neutron stars as noted earlier. The goal of projects like SETI and Breakthrough Listen is to hopefully find a signal which cannot be explained as a natural occurrence. There have been tantalizing moments, such as the "Wow!" signal in the 1970s, but nothing definitive yet. It was also thought that pulsars might be caused by ET until it was found that they were a new and bizarre type of natural phenomena.
At the moment, the assumption is that FRBs are also a natural phenomenon, but we simply don't know yet. It is most likely that they are, given past experience, but it would also be premature to say they can't be. The fact that one of them at least is now known to repeat means it can be studied further. One of the problems with trying to confirm alien radio signals, such as with the "Wow!" signal, is that the most promising candidates never repeated, meaning they couldn't be examined closer. Now we finally have some interesting signals which are repeating.
FRBs definitely deserve to be studied further, even if they are "just" natural radio emissions. They would still be a bizarre new phenomenon for scientists to scratch their heads over. The universe is full of many weird and wonderful things on its own, but if FRBs turned out to something else, that would of course be a revolutionary discovery.