One of the newest and most mysterious sky events is the fast radio burst – a brief pulse of intense energy of varying length and frequency coming usually from other galaxies but occasionally originating in the Milky Way. As astronomers became better at picking them up, their strange behavior became stranger instead of explainable. A good example is FRB121102 – first detected in 2012 in the direction of Auriga in the northern hemisphere using the Arecibo radio telescope. Since then, it has became the most active FRB and the target of the aptly-named Five-hundred-meter Aperture Spherical radio Telescope (FAST) in southwest China, which recently tallied the number of FRBs from FRB121102 and came up with a shocking total.
“Here we report the detection of 1,652 independent bursts with a peak burst rate of 122 h−1, in 59.5 hours spanning 47 days.”
The journal Nature reports that FAST users Prof. LI Di and Dr. Wang Pei from National Astronomical Observatories of Chinese Academy of Sciences (NAOC) watched as FRB121102 emitted 1,652 independent bursts during the 47 days between Aug. 29 and Oct. 29, 2019. That’s a record for the largest set of fast radio bursts and raises a number of questions, with the most obvious being, “What the heck is sending those fast radio bursts?”
"The total energy of this burst set already adds up to 3.8% of what is available from a magnetar and no periodicity was found between 1 ms and 1000 s, both of which severely constrains the possibility that FRB 121102 comes from an isolated compact object."
In a press release, Dr. Wang Pei rejects the magnetar theory (magnetars are highly magnetized neutron stars) because emitting this amount of energy would probably destroy it. However, FRB 121102 was the first known repeater and now the most active, so if they’re not coming form one source, it’s a lot of sources in one tight formation – and those sources are pretty efficient at what they do.
“The high burst rate also implies that FRBs must be generated with a high radiative efficiency, disfavouring emission mechanisms with large energy requirements or contrived triggering conditions.”
That’s science-speak for ”We know what it isn’t, but we still don’t know what it is.” One thing Li Di and the rest of the researchers do know is this:
“As the world's largest antenna, FAST's sensitivity proves to be conducive to revealing intricacies of cosmic transients, including FRBs.”
Pat yourself on the back, Five-hundred-meter Aperture Spherical radio Telescope – you’re proving yourself to be more than just the world’s largest bowl of leaves.