Astronomers have discovered their 22nd fast radio burst (FRB) and it has them buzzing. This is because the mysterious signal, which only lasted a few milliseconds, had to cross a very special region of the Milky Way to get to us.
The signal, known as FRB 150215, was detected as it happened on February 15, 2015, by the Parkes Telescope in Australia, a facility that has now become synonymous with the hunt for FRBs. The study has been accepted for publication in the Monthly Notices of the Royal Astronomical Society.
Finding FRB 150215 is great enough in itself, but it’s even better than other detections as it was recorded live. This allowed astronomers to collect a lot more information, like the polarization of the radio light. When light is polarized, the electrical fields point in the same direction. The team measured that 43 percent of the light from FRB 150215 was linearly polarized.
Out of the 22 known FRBs, only four had their polarization measured. One with no polarization, one with linear, one circular, and one both linear and circular. For FRB 150215, researchers were able to go one step further. They measured the Faraday rotation of polarization due to magnetic fields. That allowed them to work out the magnetic fields between us and the source. The more magnetic fields, the bigger the Faraday rotation.
And what they discovered is that this quantity was zero for FRB 150215. This signal traveled through a dense region of the Milky Way that has, surprisingly, very little magnetic interaction. This is pretty weird.
“This FRB seems to have found a very unusual sightline through the Galaxy, perhaps why we managed to find it given such a dense foreground,” lead author Emily Petroff wrote in a tweet.
The researchers tried to look at what actually produced the signal. They were able to quickly follow-up the detection with 11 telescopes. These instruments looked for signals in gamma-ray, radio wave, X-ray, optical, and neutrino emissions, but they weren’t able to find the source.
“No precise location was determined for FRB 150215; however, the observational evidence from the burst itself is consistent with an origin outside the Milky Way,” the team wrote in the paper.
So far, only FRB 121102 has had its source identified. And that’s a source like no other since it’s an FRB that repeats itself. Astronomers are still unsure of what causes these signals, but every single one gives us more clues about where they come from.