Context: Researchers discovered a remote blast of cosmic radio waves that lasted less than a millisecond in June 2022. This “fast radio burst” is the most distant ever detected and its source is in a galaxy that took eight billion years to reach Earth. It is also one of the most energetic ones ever observed. In a fraction of a second, it released the equivalent of 30 years of emissions from our Sun.
Fast Radio Bursts
- Fast radio bursts are sudden releases of powerful radio waves that last just milliseconds.
- In that time, they discharge as much energy as 500 million Suns. Most of them flare just once, making them unpredictable and difficult to study.
- Origin: The origin of FRBs is still mysterious. However, one leading theory is that they are caused by magnetars.
- Neutron stars are the incredibly dense remnants of supermassive stars (with masses around 1025 times the mass of the Sun) that have exploded as supernovae.
- Neutron stars are about 12 miles (20 km) in diameter and have breathtakingly high rotation speeds – they have rotational periods that can be just 0.3 to 12.0 seconds.
Types of Neutron Stars
- Pulsars: Pulsars are a type of neutron star that emits an electromagnetic beam from their poles The difference between pulsars and neutron stars is that other neutron stars do not shoot a pulse (beam) as strong as pulsars.
- Pulsars rotate so fast (many times per second) that they generate an electric field that accelerates protons and electrons through their axis. These shoot out like a beam of electromagnetic radiation out of their poles.
- Pulsars rotate so fast because even after the supernova, the momentum of the star remains, but since the resulting neutron star is many times smaller than the original massive star, it spins at a much faster rate. (In accordance with the principle of conservation of angular momentum)
- Magnetars are types of neutron stars that have much more powerful magnetic fields than normal neutron stars. They are the most powerful known magnetic objects in the Universe.
- Magnetars have magnetic fields in the range of 1015 gauss and they emit energy in the range given by luminosities of 1037 – 1040 joules per second.
- The luminosity of the sun is in the order of 1026 joules per second.
- In 2020, for the first time, a fast radio burst was detected from inside the Milky Way – which enabled scientists to trace the very star that emitted it (that star was a magnetar).
- A possible explanation for these colossal eruptions could be that:
- The magnetic field of magnetars is so powerful that it distorts the magnetar’s shape, exerting an outward pull.
- Meanwhile, the density of the collapsed stellar core results in a powerful inward gravitational pull.
- The tension between these two opposite forces causes the magnetar to rupture and quake, releasing powerful flares and large amounts of electromagnetic energy in the form of radio waves – fast radio bursts.
- Plots that compare the energy and time distributions of fast radio bursts and quakes produce similar graphs. The results show notable similarities between FRBs and earthquakes and meanwhile, there was no notable similarity with solar flares.
- Starquakes in neutron stars have opened up the possibility of gaining new insights into very high-density matter and the fundamental laws of nuclear physics.