The first repeating fast radio burst discovered by scientists is still somewhat the black sheep in the fast radio burst family. But that now seems to be changing.

Scientists have discovered a fast radio burst that in many ways resembles the very first repeating fast radio burst known as FRB 121102. Nature†

What are fast radio flashes?
Fast radio bursts are huge explosions in space that release a huge amount of energy in a short time. Very concretely, it often concerns eruptions in which more energy is released in 1 millisecond than our sun generates in 80 years. The first fast radio burst was discovered in 2007. Since then, many more fast radio bursts have been found scattered across the universe.

FRB 190520

The new fast radio flash – designated FRB 190520 – was first spotted in 2019 by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in China. Follow-up observations with the same telescope then showed that the fast radio flash – unlike most other fast radio flashes – repeatedly appears.

Location

In addition, thanks to observations with the Karl G. Jansky Very Large Array (VLA) in the US managed to locate the source of the fast radio burst. And visible light observations from the Subaru telescope in Hawaii then indicated that the radio burst originated in the outer regions of a dwarf galaxy about 3 billion light-years away from Earth. And finally, observations by the VLA show that FRB 190520 constantly emits much weaker radio waves between the radio pulses.

Agreements

“These characteristics (the repetitive character, the constant emission of radio waves and the location, ed.) ensure that this fast radio flash is in many ways reminiscent of the first fast radio flash whose location – also with the help of VLA – in 2016 determine,” said researcher Casey Law.

Stranger in our midst

That fast radio burst whose location was pinpointed in 2016 has always been a bit of an odd one out. First of all because of the repetitive nature; only five percent of the fast radio bursts discovered to date have been heard several times. In addition, FRB 121102 – unlike all other fast radio flashes that we knew until recently – also constantly emits radio waves between the radio pulses. But now there is FRB 190520: a fast radio flash that also repeatedly makes an appearance, also emits radio waves in the meantime and, like FRB 121102, resides in a galaxy at a distance of three billion light-years from Earth.

Black sheep?

And with that, the fast radio flash family now has two black sheep (of which FRB 190520 is, among other things, even more strange than FRB 121102 due to its extremely active character, among other things. “And that raises some important questions,” said Law. Because are FRB 121102 and FRB 190520 really black sheep? Or are they really just a family of their own? The differences that exist between FRB 190520 and FRB121102 and all other fast radio bursts gently hint that this could certainly be the case. In that scenario there would therefore be two ‘types’ of fast radio bursts, each of which arises in a different way. That has certainly not yet been proven. It is also still possible that all fast radio flashes originate in the same way, but behave differently depending on their age, for example.

It is still unclear exactly how fast radio bursts occur. But researchers do have ideas about it. For example, the radio bursts could be generated by neutron stars that are formed when massive stars explode or by magnetars (neutron stars with very powerful magnetic fields). “Research on fast radio bursts is very fast now and new discoveries are announced monthly,” said researcher Sarah Burke-Spolaor. “But big questions remain. And this object (FRB 190520, ed.) gives us some challenging clues in that regard.”