Vicky Kaspi is the recipient of this year’s Gerhard Herzberg Canada Gold Medal for Science and Engineering, the highest honour bestowed by the Natural Sciences and Engineering Research Council of Canada (NSERC). Photo courtesy of McGill University McGill University PhD student Paul Scholz had a eureka! moment last November as he sat at his computer, sifting through results from observations made by the Arecibo radio telescope in Puerto Rico.
The data showed several cosmic bursts with properties consistent with those of a fast radio burst (FRB) detected in 2012 mysterious split-second pulses that appeared to come from deep in outer space, beyond our galaxy. Ten bursts in all were found in the data and they have raised a deep space mystery that has baffled and excited scientists. The repeat signals were surprising and very exciting, said Scholz, who quickly called over his fellow researchers to look at his screen and share the news.
Astronomers have searched the sky in vain for repeat bursts until now. All previously detected FRBs appeared to be one-off events, thought to involve cataclysmic incidents which caused the type of spectacular explosion that could be seen across the universe and destroyed the source. Possible explanations included a star exploding in a supernova or a neutron star collapsing into a black hole.
In a paper published in Nature on Wednesday, the new finding indicates something different, or possibly points to a subclass of FRBs. It shows that at least some FRBs have other origins and likely come from an extremely powerful object that can produce multiple bursts in under a minute. Now that we have repeat bursts, it looks like they can survive the event, Scholz said in an interview.
We re thinking it looks like it might be a pulsar in another galaxy that is emitting pulses that are quite a bit brighter than any we ve seen in our galaxy. In that sense, it would be unprecedented. These extraterrestrial bursts likely occurred billions of years ago and certainly offer no proof of life in the universe they were much too distant, and much too strong, to have been caused by a civilization sending a signal, friendly or otherwise.
But the discovery does suggest the bursts emanated from something exotic, such as a rotating neutron star with unprecedented power. (A neutron star is the most dense thing in the universe after a black hole; it can be the size of a city with the mass of the sun packed into it and some rotate once per millisecond.) It was probably some extreme object like that, said Scholz, who is doing his PhD in astrophysics under the direction of Vicky Kaspi, the renowned McGill astrophysicist who heads the McGill Space Institute and just won the prestigious Killam Prize for academic-career achievement. The finding is the result of an international collaboration called PALFA for which Kaspi is principal investigator that includes researchers from Canada, the U.S., the Netherlands, the U.K. and Germany.
While it has shed some new light on FRBs, it also raises many questions. One of the team s next objectives is to determine where the radio bursts originated, possibly using a technique called interferometry. Finding the galaxy it s coming from would tell us about the environment it s coming from, said Scholz.
To date, only 17 FRBs have been found (the McGill team s 11 radio bursts count as one FRB source), so much is left to discover about this powerful, enigmatic phenomenon. Knowledge of FRBs may really start to advance when Canada s CHIME (Canadian Hydrogen Intensity Mapping Experiment) radio telescope becomes operational. It will be able to produce a map of cosmic structure over the largest volume of the universe ever observed.
It will definitely open a big window on FRBs, said Scholz.
And he and his team will eagerly be looking through it.
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