On 9 January 2019, a group of Canadian-led astronomers working with a radio telescope dubbed CHIME, published a study announcing the second registered instance of a "Fast Radio Burst" or repeated FRB. Although the non-repetitive FRBs have been known to science since 2007, the mechanisms that produce them remain largely a mystery. These millisecond explosions of electromagnetic radiation, necessarily produced by high-energy events, reach the Earth from sources to billions of light years away, where they are detected by large ranks of radio telescopes. Until recently, FRBs were exclusively singular, transient events that made them difficult to study or understand with depth or precision.
CHIME's findings, which included 12 non-repetitive FRBs in addition to the second that was always repeated, were made before that the telescope is even fully operational. The authors have argued that these results may open the possibility that the repetition of FRB is a common feature of our universe. In their study, published in the scientific journal Nature the authors concluded that "CHIME / FRB, with its wide field and high sensitivity, would have to find a large population of repeaters, if they exist. Our first 13 repeats events suggest that there is indeed a large population. "
If you have heard of this discovery from an outlet other than Nature however, you may have the impression that a protagonist l & # 39; hypothesis for the source of these radio explosions was a kind of alien technology:
- Mysterious fast radio burst by Deep Space & # 39; Could Be Aliens & # 39; ( The Guardian )
- Mysterious repeated radio signals have reached the Earth from a galaxy 1.5 billion light years away (but are evidence of alien civilization?) ( Daily Mail ).
- Alien signals? More bizarre "gusts of fast radios" detected from outer space ( USA Today )
Of course, anything "could be" alien, but because such an argument is noteworthy it should have been done with relevant evidence. The CHIME document did not attempt to present such an argument and therefore did not provide any specific evidence in favor of any alien technological scenario. Instead, this document showed that the same narrow region of space emitted huge amounts of radio energy more than once.
Nearly all the outlets that suggested an alien mechanism connected to FRB cited the same speculative statements of the astronomer of Harvard Avi Loeb. In 2017 (in a paper not related to the study currently reported), Loeb suggested that a possible source of FRB could be an alien civilization that radiates radio waves in order to push distant light sails, thin objects accelerated by the pressure of solar radiation. Loeb, it should be noted, was also the main scientific voice that fed the media reports that an object discovered passing through our solar system towards the end of 2018, & # 39; Oumuamua, was an alien light sail.
Loeb has a strong interest in light sails. He is the chairman of an advisory committee for a project called Breakthrough Starshot, which aims to send a light sail to the star closest to our sun. His analyzes do not attempt to prove an alien mechanism for these various FRB events, simply to show that such scenarios are possible in our understanding of the physical laws of the universe, and could involve a light sail. Although fascinating, the subject is (from a scientific point of view) a distraction from the real scientific progress made by the CHIME team.
CHIME, which stands for Canadian Hydrogen Intensity Mapping Experiment, was originally built to detect the radio emissions of hydrogen coming from deep within the primordial past of our universe. The ability to distinguish extremely weak radio sources through a huge sky sample, however, makes it a perfect tool to monitor FRBs as well. It is not that FRBs are rare: some estimates suggest that a FRB occurs somewhere in the sky every eight seconds. It's that the universe is big enough, and you have to constantly observe a large area of sky to detect a FRB and, and an even greater amount to find an instance of a repeated one.
With the large amount of sky captured by the highly sensitive CHIME radio telescope, experts predicted that it would lead to the discovery of a much larger number of FRBs and even repeat FRBs. Based on the initial results in Nature their hypothesis seems to have been confirmed. In a three-week period in August 2018, the CHIME telescope detected 13 FRBs, and one of them was a repeater. Speaking with The Guardian astrophysicist of CHIME and professor of the University of British Columbia, Ingrid Stairs, said: "Until now, there was only one known repeater FRB. another suggests that there could be more out there, and with more repeaters and more sources available for study, we might be able to understand these cosmic puzzles – where they come from and what causes them. "
The astrophysics of West Virginia University, Sarah Burke-Spolaor, was part of the team that identified the position of the first recurrent FRB known to science, a weak dwarf galaxy about 2.5 billion light years away. This knowledge allowed the team to perceive the energy behind the event that produced radio waves, as described in Science News in January 2017: "For about five milliseconds, the burst has he eclipsed all the stars in his galaxy and rivaled the luminosity of incandescent disks of gas that revolved around supermassive black holes, said Burke-Spolaor, one of the researchers involved in the project. "
Speaking by telephone, Burke-Spolaor, who was not part of the CHIME study, told us that "the two main hypotheses [for what causes FRBs] at this time, more or less, are a sort of black hole origin or some kind of neutron star origin. "Neutron stars are the collapsed nucleus of giant stars that can emit radiation of electromagnetic radiation. "It would be [have to] to be a very extreme neutron star … much more energetic than what we see in our galaxy" to propagate radio waves for billions of light years, said Burke-Spolaor.
Some scientists, including members of the CHIME team, pose scenarios that involve a combination of neutron stars and supermassive black holes. This existence of a black hole is supported by the observation that the radio impulses that make up most of the newly discovered FRBs are "dispersed" in a way that betrays high energy or a "special" environment. Speaking with The Guardian CHIME team member Cherry Ng explained "This could mean in a dense group like a supernova remnant or near the central black hole in a galaxy, but it must be somewhere special to give us all the dispersion we see. "
Outside of being a scientific mystery that could one day be resolved while the more repeated FRBs are discovered by large telescopes like CHIME, these FRBs could also be a tool to help us better understand the 39, the immense emptiness of our universe. In a commentary of 18 November 2018 on Nature Astronomy Burke-Spolaor claimed that the FRBs provided science with a "rich set of data with which to probe" both the mechanisms that produce the bursts and the nature of the intergalactic medium that they travel through. "Gravitational waves, neutrinos and the full electromagnetic spectrum are now open to business," he wrote.
"Until recently, there were more theories [about FRBs] of actual radio blasts," Burke-Spolaor joked. With these early results of CHIME, this balance could change.