The universe appears to be full of strange radio signals that come and go so quickly that their sources are difficult to locate. As such, we don’t really know what causes these fast radio bursts (FRBs). But now astronomers have traced one back to its home galaxy – the closest one yet – which could help unravel the mystery.
The name given to this phenomena tells you basically everything you need to know. These signals are incredibly fast, usually lasting just milliseconds. They’re made up of radio waves. And they burst with huge amounts of energy.
Dozens of FRBs have been detected since their discovery in 2007, and they seem to fall into two main categories. Most appear to just fire off once and are never heard from again, while others repeat at irregular, unpredictable intervals. Scientists don’t really know what causes them, and there may be separate causes for repeaters versus one-offs.
Figuring out where they’re actually coming from is, of course, a major step towards determining what causes them. In the new study, an international team of astronomers has pinpointed the location of a repeating burst known as FRB 180916, and it’s the closest signal ever located.
“Identifying the host galaxy for FRBs is critical to tell us about what kind of environments FRBs live in, and thus what might actually be producing FRBs,” says Sarah Burke-Spolaor, co-author of the study. “This is a question for which scientists are still grasping at straws.”
The team tracked the signal to an area about seven light-years wide, placing it in a galaxy called SDSS J015800.28+654253.0, which is about 500 million light-years from Earth. That might sound like quite a distance, but it’s a cosmic stone’s-throw considering that most others are more than 3 billion light-years away.
That makes this the fifth FRB whose source galaxy to have been located, and only the second repeating signal. Interestingly though, this one seems to be residing in a very different environment to the first one, which confounds the mystery even further.
In 2018, astronomers found that FRB 121102 – the first repeater ever discovered – was in a star-forming dwarf galaxy. Its emissions seemed to be twisted, leading scientists to speculate that it was located near a huge black hole or inside a nebula. But FRB 180916 appears to be in a much calmer area of a galaxy much like our own.
“What’s very interesting about this particular repeating FRB is that it is in the arm of a Milky Way-like spiral galaxy, and is the closest to Earth thus far localized,” says Kevin Bandura, co-author of the study. “The unique proximity and repetition of this FRB might allow for observation in other wavelengths and the potential for more detailed study to understand the nature of this type of FRB.”
The research was published in the journal Nature.
Source: West Virginia University
