Mysterious radio bursts - incredibly powerful and short signals - can create debris from planets that are blasted away by neutron stars, showering them with their harsh radiation.
In 2007, astronomers first spotted a strange signal - a brief but exceptionally powerful burst in the radio band. Its unknown, compact and distant source emitted as much energy in a few milliseconds as the Sun loses in a few days. Since then almost a hundred such Fast Radio Bursts (FRBs) have been recorded, but their nature remains a mystery.
Most likely, they are associated with superdense neutron stars, or with magnetars - neutron stars with huge magnetic fields. However, there are other theories that link FRBs to hypothetical quark stars and even to communications from extraterrestrial civilisations. In an article published in The Astrophysical Journal, Chinese astrophysicists put forward a new idea: fast radio bursts can create planets that die if they come too close to neutron stars.
Planets may indeed exist near such extreme objects. Yong-Feng Huang of Nanjing University and his colleagues have simulated a system consisting of a neutron star and a planet orbiting a tight and highly extended orbit. By moving closer and farther away from the star, the planet is subject to powerful tidal forces in its heterogeneous gravitational field. Thanks to these forces, the star "bites off" from the planet piece by piece.
The star also bites off relatively small fragments, no larger than a few kilometres, which can produce radio bursts. A neutron star emits a stellar wind much stronger than an average star like the Sun. Under the influence of this flux of particles and radiation, a cloud of fragments from a dying planet can emit brightly in the radio spectrum. As such debris flies between the neutron star and us observing it from Earth, instruments pick up this radiation as a fast radio burst.
Using data from two previously recorded bursts, FRB 121102 and FRB 180916, scientists have shown that this scenario can explain both their periodicity (157 and 16.4 days, respectively) and brightness. New long-term observations of similar repetitive radio bursts may help to confirm or refute the hypothesis. If they are really produced by planets near neutron stars, the orbits of such planets should degrade rather quickly. The orbital changes should affect the character of the next bursts, which can be observed on the scale of a few years.
