A new hypothesis tries to give a credible explanation for the mysterious radio bursts known as FRB 121102. These radio bursts could be emanating from a neutron star near a supermassive black hole.

In 2007, scientists were digging through archival data of a 6-year pulsar survey of the Magellanic Clouds. These are two nearby dwarf galaxies visible in the Southern Hemisphere. Researchers were surprised by what they found.

parked 64 meter radio telescope
Parkes 64 meter radio telescope in New South Wales, Australia | Stuart Duff, CSIRO (used by Swinburne with permission) | Astronomy.swin.edu.au

Using data from radio telescopes like the Parkes 64 meter radio telescope, pictured to the left, intense bursts of radio emission were discovered. These bursts lasted a few miliseconds at most and “exhibit[ed] the characteristic dispersion sweep of radio pulsars,” according to Swinburne Astronomy. They were found near the Small Magellanic Cloud.

the magellanic clouds
The Magellanic Clouds: two irregular dwarf galaxies, one larger and one smaller, that are orbiting the Milky Way Galaxy. | CC by 4.0 | Wikimedia

Discovered by Lorimer et al. and thereby known as the Lorimer Burst, these intense and brief pulses were thought to be unique. A Swinburne student, Sarah Burke-Spolaor later found conflicting radio burst behind readings of the Lorimer Burst. Consequently, interest in these bursts dwindled.

Then, in 2013, more dramatic radio emissions were discovered. Thornton et al. found four “Lorimer Bursts” and reclassified them as Fast Radio Bursts (FRBs). Parkes 64 meter radio telescope found these bursts as a part of the High Time Resolution Universe Surveys.

first extragalactic radio burst
“The first extragalactic radio burst.” | Swinburne | Astronomy.swin.edu.au

Over the past decade, over three dozen FRBs have been detected and classified. Yet, they remained a mystery and scientists have proposed several scenarios as to their origin.

One proposal is that the brightest of these FRBs could be from extra-terrestrial life. According to Swinburne with regards to Thornton et al.’s findinds: “The brightest burst exhibited a classic dispersion sweep and showed scatter-broadening with power law dependencies exactly like we’d expect from true extra-terrestrial sources of radio emission.

Where do Fast Radio Bursts Come From?

Before 2012-13, one of the challenges in studying the nature of FRBs was that they hadn’t repeated frequently. This prevents follow-up comparisons after initial detection.

Recorded data can be analyzed. However, as we mentioned, there were years between these detection events.

At first, astronomers hypothesized that because they don’t repeat, FRBs may originate from violent cosmic events. For example, a collapsing star or two black holes merging. These could potentially explain the intense energy released.

Stars Orbiting Supermassive Black Hole
Artist rendering of stars orbiting a supermassive black hole | ESO | M. Parsa | L. Calçada

Despite many research efforts, astronomers hadn’t conclusively traced FRBs back to any known high-energy phenomena. The origin of FRBs remained an enigma.

One FRB packs enough energy for humanity to run for over 10 trillion years. #EatthatElonClick To Tweet

Since 2012, scientists have reevaluated what they thought they knew about FRBs. The first-ever repeating FRB, FRB 121102, was detected and localized.

FRB 121102, was first detected, as all FRB names are categorized, on November 2nd, 2012. Three years later, another 16 high-energy bursts were detected. Then, 9 more in 2016–all seeming to be emanating from the same source.

The repeating pulses led to the logical conclusion that FRBs don’t result in the destruction of the event host. In other words, their origin may not be as cataclysmic an event as previously thought.

Despite that, we still wouldn’t want this source close to us. We’ll get into that a little later.

In 2016, the FRB 121102 source was identified as lying in a dwarf galaxy, about three billion light-years away from Earth. However, the location still didn’t explain what could possibly have caused FRBs in the first place.

An Alien Signature or a “Magnetar”?

FRBs are transient and very strong. Lasting less than 5 milliseconds, one burst yields enough energy for humanity to run for over 10 trillion years. As recently proven, these bursts can repeat and appear to be polarized beams of energy.

This led some astronomers to suggest that FRBs could be a signature of an alien civilization far, far away. Harvard researchers seriously investigated this hypothesis and said that FRBs might be leakage from artificial transmitters used to power alien spaceships.

But now, a new study suggests that the only FRB known to repeat, FRB 121102, could originate from a neutron star that’s hiding in the vicinity of a massive black hole.

An international team of astronomers found that whatever the source of FRB 121102, it’s powerful. In fact, it’s surrounded by an extremely powerful magnetic field that causes the burst to “shout and twist.”

This twisting describes the phenomenon called Faraday rotation. It is caused by the radio burst traveling through a high magnetic field. Likely, this field would be encased in dense plasma. Scientists thus believe that that the FRB 121102 must have come from near a black hole, a nebula-cradled neutron star, or some remnant of a supernovae.

Similar phenomena have been documented previously and traced back to neutron stars orbiting the supermassive black hole in our own Milky Way. Researchers said the source of FRBs could be young, fast-rotating, and highly magnetized neutron stars, also known as “magnetars”.

“The bursts may therefore come from a neutron star in such an environment,” said researchers in the study. “Or could be explained by other models, such as a highly magnetized wind nebula or supernova remnant surrounding a young neutron star.”

George Feldstein Professor of Astronomy James Cordes says “We estimate the magnetic field and gas density surrounding the blast source, and we can link them, for example, with a model involving a young magnetar – a neutron star with an especially large magnetic field – to the central engine that produces the bursts.

Cordes continues: “This is exotic. If we had one of these on the other side of our own galaxy – the Milky Way – it would disrupt radio here on Earth, and we’d notice, as it would saturate the signal levels on our smartphones. Whatever is happening there is scary. We would not want to be there.

At least, we wouldn’t want to be there with our smartphones.

Do you think this is a valid hypothesis to explain this phenomenon? Or is something else more likely?

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