For the first time, the source of a unique fast radio burst has been identified
– News of July 2, 2019 –
In 2007, while digging into old archives of the Parkes observatory in Australia, a student made a strange discovery. The radio telescope appeared to have recorded a very short radio burst in 2001 that did not correspond to any known type of source. In the last ten years, however, other similar signals have been detected. Fast radio bursts (FRB) have become a subject of study although we still do not know what causes them.
The mystery deepened in 2014 when an American astrophysicist identified a source of repeated fast radio bursts called FRB 121102. They sometimes remain silent for years before issuing a dozen bursts over several minutes. The last time was in 2017. The repetition of the signals made possible to identify the source, a dwarf galaxy located 3 billion light-years away from us. It’s a very active galaxy that produces a lot of new stars.
In 2019, there is still no explanation of the physical phenomenon that allows these signals to exist. Worse, perhaps two different explanations could explain unique signals and repeated signals. Failing to understand, we continue to observe. In a study published on June 26, a team announced that it has been able to identify the source of a unique fast radio burst, which is a first. They used an Australian observatory specialized in detecting fast radio bursts. The observatory has identified nearly a third of those known to date. The discovery was allowed because the 36 antennas of the observatory pointed that day in the same direction. This allowed to compare the the signals to isolate the source in a very precise way. This is once again a distant galaxy located about 4 billion light-years from the Milky Way.
It does not look like the FRB 121102 host galaxy at all. It’s old, as big as the Milky Way, and does not create a lot of stars. Moreover, the source does not seem to come from the center of the galaxy. It appears to be thirteen thousand light-years from the center of the galaxy, suggesting that supermassive black holes would not be the cause of these fast radio bursts. It is not sure that this observation allows to know more. Many more or less credible hypotheses have been formulated to explain these mysterious radio signals. Extraterrestrials, magnetars, cosmic strings have been mentioned for example.
The origin of fast radio bursts (FRB) is always a mystery
– News of January 13, 2019
In recent days, there has been a lot to say about fast radio bursts, the FRB. This phenomenon is still poorly understood and becomes even more intriguing. In 2007, David Narkevic, then a student at the West Virginia University, met his teachers with a strange discovery after searching in old data from the Australian Parkes radio telescope. He identified a very strong and very short signal in the region of the sky near the little cloud of Magellan. Subsequent analyzes show that the signal was unique and that its origin was probably extragalactic. The signal does not correspond to any known cosmic event. The astrophysicists were perplexed.
At the beginning of 2010, we start to detect other similar signals, at Parkes and other observatories. Some of the signals detected at Parkes were eliminated when we realized that they were of terrestrial origin. We discovered that the opening of microwaves doors by observatory scientists create a parasitic signal very similar to that of a FRB. Nevertheless, the cosmic phenomenon is real. Other observatories also identify signals similar to that discovered by David Narkevic in 2015.
In 2015, the mystery grows when we discover a new source of fast and repeated radio bursts, but this time with dozens of bursts spread over several years. The same year began the construction of the CHIME radio telescope in Canada. It had to be particularly effective in discovering new FRBs. It has barely been put into operation when it identifies the second source of repeated FRBs. It is therefore a new type of radio signal which origin seems extragalactic and can be repeated or not. We must now find an explanation for the phenomenon.
Some hypotheses have already been formulated. Of course, the possibility that it is a signal of an intelligent civilization has been relayed in the press around the world. The situation is somewhat reminiscent of the discovery of pulsars in the 1960s. A repeated and unexplained radio signal necessarily evokes aliens, but there is a good chance that the FRB is of natural origin.
It may be necessary to look for two different origins. Supernovae, neutron stars or black holes, or active nuclei of galaxies could be responsible of single or repeated signals. Almost all assumptions are open. Meanwhile, CHIME continues to capture FRBs.
Image by Jingchuan Yu, Beijing Planetarium