Cosmic radio signals are beaming to Earth every day – and astronomers are stumped as to their origin. Now a new study finds evidence that these signals, known as fast radio bursts (FRBs), could be caused by “starquakes.”
The name of this phenomenon tells you pretty much everything you need to know – these signals are bright bursts of radio waves that are gone in a flash. Thousands of FRBs have been detected since their initial discovery in 2007, some that are one-off events and others that repeat on either predictable or random timeframes.
Exactly what was causing them remains a mystery, but with so many FRBs on record now astronomers have been able to make some educated guesses. Some have been traced to neutron stars – the collapsed cores of massive stars – and in particular, those with extremely powerful magnetic fields, known as magnetars. Even so, it’s still hard to explain how these objects would produce the signals.
But now we may be closer to an answer. Scientists at the University of Tokyo have analyzed the time-energy correlation of thousands of FRBs from repeating sources, and compared them to other high-energy events. Solar flares have been a strong contender as an explanation, but intriguingly the team found distinct differences between those and FRBs. There was, however, a surprising similarity between FRBs and earthquakes.
“First, the probability of an aftershock occurring for a single event is 10-50%,” said Professor Tomonori Totani, co-author of the study. “Second, the aftershock occurrence rate decreases with time, as a power of time; third, the aftershock rate is always constant even if the FRB-earthquake activity (mean rate) changes significantly; and fourth, there is no correlation between the energies of the main shock and its aftershock.”
So what does all this mean to those of us not well-versed in statistical analysis? The team says the findings suggest that FRBs might not be produced through flares from neutron stars but from “starquakes,” which suddenly release huge amounts of energy. The weirder implication there is that some neutron stars may actually have solid crusts for these quakes to occur on – a hypothesis backed up by recent X-ray observations of a magnetar.
Such a strange hypothesis will of course require more study to confirm or rule out. And with so many FRBs occurring regularly, there’s no shortage of data to pore over.
The research was published in the journal Monthly Notices of the Royal Astronomical Society.
Source: University of Tokyo
