Research From University of Tokyo Links Fast Radio Burst to Starquakes on Neutron Stars

Saturday - October 21 2023, 14:39 UTC - 1 year ago

New research at the University of Tokyo has found similarities between Fast Radio Bursts and earthquakes, suggesting that at least some FRBs are caused by starquakes on the surface of neutron stars. This discovery could help us better understand earthquakes, the behavior of high-density matter, and aspects of nuclear physics.

Fast radio bursts, or FRBs, are an astronomical mystery, with their exact cause and origins still unconfirmed. These intense bursts of radio energy are invisible to the human eye, but show up brightly on radio telescopes. Previous studies have noted broad similarities between the energy distribution of repeat FRBs, and that of earthquakes and solar flares.

However, new research at the University of Tokyo has looked at the time and energy of FRBs and found distinct differences between FRBs and solar flares, but several notable similarities between FRBs and earthquakes. This supports the theory that FRBs are caused by "starquakes" on the surface of neutron stars. This discovery could help us better understand earthquakes, the behavior of high-density matter, and aspects of nuclear physics.

The vastness of space holds many mysteries. While some people dream of boldly going where no one has gone before, there is a lot we can learn from the comfort of Earth. Thanks to technological advances, we can explore the surface of Mars, marvel at Saturn’s rings, and pick up mysterious signals from deep space. Fast radio bursts are hugely powerful, bright bursts of energy that are visible on radio waves.

First discovered in 2007, these bursts can travel billions of light years but typically last mere thousandths of a second. It has been estimated that as many as 10,000 FRBs may happen every day if we could observe the whole sky. While the sources of most bursts detected so far appear to emit a one-off event, there are about 50 FRB sources that emit bursts repeatedly.

The cause of FRBs is unknown, but some ideas have been put forward, including that they might even be alien in origin. However, the current prevailing theory is that at least some FRBs are emitted by neutron stars. These stars form when a supergiant star collapses, going from eight times the mass of our sun (on average) to a superdense core only 20-40 kilometers across. Magnetars are neutron stars with extremely strong magnetic fields, and these have been observed to emit FRBs.

"It was theoretically considered that the surface of a magnetar could be experiencing a starquake, an energy release similar to earthquakes on Earth," said Professor Tomonori Totani from the Department of Astronomy at the Graduate School of Science. "Recent observational advances have led to the detection of thousands more FRBs, so we took the opportunity to compare the now large statistical data sets available for FRBs with data from earthquakes and solar flares, to explore possible similarities." .

So far, statistical analysis of FRBs has focused on the distribution of wait times between two successive bursts. However, Totani and co-author Yuya Tsuzuki, a graduate student in the same department, point out that calculating only the wait-time distribution does not take into account correlations that might exist across other bursts. So the team decided to calculate correlation across two-dimensional space, analyzing the time and energy of over 1,400 FRB sources.

The study revealed that the peaks of the distributions of wait times and energies of FRBs and their corresponding repeats are far apart for solar flares, indicating that the two have significantly different behaviors. However, this was not the case for earthquakes, whose distributions indicated strong correlation between the release time and the total energy of the events. FRBs showed a similar trend to earthquakes.

The analysis showed that the two-dimensional correlation of FRBs and earthquakes are also nearly similar, suggesting that both are driven by the same kind of bursting energy. Thus, unlike the solar flares, FRBs appear to be linked to some kind of release of energy at the surface of the neutron star, called a starquake.

It is still unclear what a starquake is, but the research team are confident that the answer lies in the behavior of high-density matter inside the neutron star. The next step is to explore this further. Understanding starquakes could help us understand earthquakes, and contribute evidence that can inform aspects of nuclear physics. This new discovery could be just the tip of the iceberg.