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WVU astrophysicist part of research team that discovers mysterious cosmic radio bursts are found to repeat

Figure Credit: Danielle Futselaar — The 305-m Arecibo telescope and its suspended support platform of radio receivers is shown amid a starry night. From space, a sequence of millisecond-duration radio flashes are racing towards the dish, where they will be reflected and detected by the radio receivers. Such radio signals are called fast radio bursts, and Arecibo is the first telescope to see repeat bursts from the same source.A global team of astronomers, including one from  West Virginia University, have for the first time detected repeating short-duration bursts of radio waves from an enigmatic source which is likely located well beyond the edge of the Milky Way galaxy. The findings indicate that these “fast radio bursts,” or FRBs, come from an extremely powerful object which occasionally produces multiple bursts in under a minute.

The research was published online today in the journal Nature.

The first FRB was discovered in 2007 by WVU  physics and astronomy professors  Duncan Lorimer and  Maura McLaughlin, along with then-WVU undergraduate student David Narkevic. Since then scientists have been trying to find out more about where these mysterious phenomena come from and what causes them, increasing our understanding about the universe.

This original burst and all other previously detected FRBs have appeared to be one-off events. Because of that, most theories about the origin of these mysterious pulses have involved cataclysmic incidents that destroy their source – a star exploding in a supernova, for example, or a neutron star collapsing into a black hole. The new finding, however, shows that at least some FRBs have other origins.

FRBs, which last just a few thousandths of a second, have puzzled scientists since they were first reported nearly a decade ago. Despite extensive follow-up efforts, astronomers until now have searched in vain for repeat bursts.

That changed on Nov. 5, 2015, when an international collaboration including McLaughlin made a startling discovery. New data from the Arecibo radio telescope in Puerto Rico showed several bursts with properties consistent with those of an FRB detected in 2012. There were a total of 10 new bursts.

The finding suggests that these bursts must have come from a very exotic object, such as a rotating neutron star having unprecedented power that enables the emission of extremely bright pulses, the researchers say. It is also possible that the finding represents the first discovery of a sub-class of the cosmic fast-radio-burst population.

Scientists believe that these and other radio bursts originate from distant galaxies, based on the measurement of an effect known as plasma dispersion. Pulses that travel through the cosmos are distinguished from man-made interference by the influence of interstellar electrons, which cause radio waves to travel more slowly at lower radio frequencies. The 10 newly discovered bursts, like the one detected in 2012, have three times the maximum dispersion measure that would be expected from a source within the Milky Way.

Intriguingly, the most likely implication of the new finding – that the repeating FRBoriginates from a very young extragalactic neutron star – is at odds with the results of a study published last week in Nature by another research team. That paper suggested FRBs are related to cataclysmic events, such as short gamma-ray bursts, which cannot generate repeat events. However, the apparent conflict between the studies could be resolved, if it turns out that there are at least two kinds of FRB sources.

In future research, the team hopes to identify the galaxy where the radio bursts originated. To do so, they will need to detect bursts using radio telescopes with far more resolving power than Arecibo, a National Science Foundation-sponsored facility with a dish that spans 305 meters and covers about 20 acres. Using a technique called interferometry, performed with radio telescope arrays spread over large geographical distances, the astronomers may be able to achieve the needed resolution.

“Achieving localization on the sky will allow us to say exactly which galaxy this burst is coming from,” said Maura McLaughlin. “Finding the host galaxy of this source is critical to understanding its properties.”

The Arecibo Observatory is operated by SRI International under a cooperative agreement with the National Science Foundation, and in alliance with Ana G. Méndez-Universidad Metropolitana, and the Universities Space Research Association.

The research was supported by grants from the European Research Council, the National Science and Engineering Council of Canada, and the American National Science Foundation.

McLaughlin’s participation in the project is yet another example of recent discoveries being made by WVU astrophysicists. Last month, WVU announced that assistant professor  Sean McWilliams was a member of the Laser Interferometer Gravitational-Wave Observatory, or LIGO, research team that  detected gravitational waves, invisible ripples in spacetime, which verified that Einstein’s final prediction in his theory of general relativity is true.

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