Fast Radio Bursts (FRBs) are one of the biggest mysteries in the field of radio astronomy. These are radio signals lasting a few milliseconds to a few hundred milliseconds, coming from different parts of the universe and from every direction. Despite being ubiquitous, we still don’t understand FRBs very well. However, a recent discovery might bring us closer to explaining at least some of these mysterious signals.
FRBs are produced by very powerful events that release as much energy in just a few milliseconds as our sun does in a few days. Theoretically, these signals reach our planet every day, but only some are visible to us. Over the years, scientists have discovered that FRBs are produced by different types of galaxies, in different parts of galaxies, and possess different properties, including different types of polarization. Despite being common events happening all across the universe, they represented a completely new phenomenon that could not be explained as anything else.
Initially, one of the explanations for FRBs involved magnetars, super magnetized neutron stars that produce powerful radio emissions occasionally. These magnetars provided the best possible explanation as FRBs have a tendency to be extremely polarized, which requires very powerful magnetic fields. However, this didn’t explain all of the FRBs, as some were repeated, with different patterns that were too periodic to explain with a simple magnetar. This suggested that maybe FRBs are a phenomenon that seems to happen around various neutron stars, potentially generated in different ways.
Recent research suggests that some FRBs are related to the extreme powerful collisions between neutron stars. Neutron stars are incredibly dense and compact, with masses greater than our sun but only the size of a city. When two neutron stars collide, they produce an explosion known as a Kilo Nova, which is similar to a supernova but usually slightly weaker. This explosion produces very powerful gamma emissions and converts lighter elements into much heavier elements, such as gold and platinum.
During these collisions, an intermediary object is produced, which survives for a few hours before collapsing into a black hole. Some theories suggest that this object can exist as an ultra-massive neutron star that remains stable because of its powerful magnetic fields and fast rotation. During its brief existence, this object can release FRBs, which might resemble a magnetar or an extremely fast spinning neutron star.
In a recent study, scientists found a strong correlation between gravitational waves and an FRB, providing evidence that neutron star collisions might be responsible for at least some FRBs. To discover this connection, they analyzed a catalog containing all known FRBs detected in the last few years, confirming just over 500 sources. They then compared this catalog with the data from the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo.
Gravitational waves are ripples in the fabric of spacetime, produced by the acceleration of massive objects, such as colliding neutron stars. The LIGO and Virgo detectors are designed to detect these waves, and in 2017, they detected a gravitational wave signal, known as GW170817, produced by the collision of two neutron stars.
In their analysis, the scientists found that an FRB known as FRB 190608 was detected just 0.4 seconds after the peak of the gravitational wave signal from GW170817. This strong correlation suggests that the FRB was produced by the neutron star collision, providing further evidence for the theory that some FRBs are generated by neutron star collisions.
The discovery of this correlation is an exciting development in the study of FRBs, and it brings us one step closer to understanding these mysterious signals. However, many questions remain unanswered.