Astronomers discover repeated bursts of radio waves in space

posted on 08/06/2022 21:28 / updated on 08/06/2022 21:36


(credit: BILL SAXTON, NRAO/AUI/NSF)

Astronomers have found the second example of a Fast Radio Burst (FRBs) in history. The event calls into question the nature of mysterious space phenomena. The explosions are intense and through brief flashes of radio frequency emissions, which last for milliseconds.

The phenomenon was first discovered in 2007 by graduate student David Narkevic and has become commonly known as the ‘Lorimer Burst’. The source of these high-energy events is a mystery, but clues to their nature are being gathered through repetition.

The FRB is a transient radio pulse ranging in length from a fraction of a millisecond to a few milliseconds, caused by some mysterious high-energy astrophysical process that has yet to be discovered. Astronomers estimate that the average FRB releases as much energy in one millisecond (one thousandth of a second) as the Sun releases in 3 days (which is about 250,000 seconds).

The new discovery raises new questions about the nature of these mysterious objects and also about their usefulness as tools for studying the nature of intergalactic space.

The new source was detected with the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) in Guizhou, China, in 2019. Observation of the discovery was made by the Jansky Very Large Array (VLA) program in 2020. Led by Caltech, the group was able to pinpoint the location of the object, and this allowed visible-light observations with the Subaru telescope in Hawaii to show that it is on the outskirts of a dwarf galaxy nearly 3 billion light-years from Earth.

The VLA observations also found that the object constantly emits weaker radio waves between bursts.

To the National Astronomical Observatories of China (NAOC), Di Li, leader of the Commensal Radio Astronomy FAST Survey (CRAFTS), which discovered the FRB in China, highlighted that the biggest question is where the explosions come from. “One of the key questions in the field of FRBs is whether or not all sources are repeated.”

The researcher explains that another special feature is the wave dispersion measurement, which indicates that the emissions passed through the highest electron density of any FRB before being observed on Earth. This suggests that the FRB is active in a local plasma environment, such as that created by a supernova, and is a newly created source.

While providing insights into the FRB’s environment, the wide disparity in scatter measurements with other FRBs calls into question their use as “cosmic standards” for measuring distances.

Franz Kirsten, a postdoctoral researcher at the Dutch Institute for Radio Astronomy (Astron), told space.com that it would be possible to trace an evolutionary path for fast radio bursts, but with these two sources alone it is difficult to say. “We need to find more and constrain this evolutionary stage model. We really need more (radio bursts) at different ages to say ok, this thing is disappearing all the time. So what would be really nice to see is if these persistent sources were in fact disappearing with time”

Co-author Yu Wenfei told space.com that “the mechanisms responsible for the extra scatter measurement and quasi-source environment of such repeated FRBs with a PRS association are still a problem. But I am optimistic that the FRB puzzle will be solved by investigating such extreme FRBs,” said Yu.

This is why there is high value in discovering more repeated FRB sources, along with trying to get a much better picture of the environments in which they occur, for example using the Hubble Space Telescope for follow-up observations.

*Intern under the supervision of Pedro Grigori.

  • Artist's conception of a neutron star with an ultra strong magnetic field, called a magnetar, that emits radio waves (red).  magnetars are a prime candidate for what generates fast radio bursts

    Artist’s conception of a neutron star with an ultra strong magnetic field, called a magnetar, that emits radio waves (red). magnetars are a prime candidate for what generates fast radio bursts
    Photo: BILL SAXTON, NRAO/AUI/NSF

  • Artist's conception of a neutron star with an ultra strong magnetic field, called a magnetar, that emits radio waves (red).  magnetars are a prime candidate for what generates fast radio bursts

    Artist’s conception of a neutron star with an ultra strong magnetic field, called a magnetar, that emits radio waves (red). magnetars are a prime candidate for what generates fast radio bursts
    Photo: BILL SAXTON, NRAO/AUI/NSF

  • Artist's conception of a neutron star with an ultra strong magnetic field, called a magnetar, that emits radio waves (red) magnetars are a prime candidate for what generates fast radio bursts

    Artist’s conception of a neutron star with an ultra strong magnetic field, called a magnetar, that emits radio waves (red) magnetars are a prime candidate for what generates fast radio bursts

    Photo: BILL SAXTON, NRAO/AUI/NSF

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