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Explained: What is a radio burst, spotted by NASA for the first time in the Milky Way?         

8th November, 2020 Science and Technology

Context: NASA has reported that, it observed a mix of X-ray and radio signals never observed before in the Milky Way.

  • Significantly, the flare-up it observed included the first fast radio burst (FRB) seen within the galaxy.

Who discovered the simultaneous bursts in the Milky Way?

  • The X-ray portion of the simultaneous bursts was detected by several satellites, including NASA’s Wind mission.
  • The radio component was discovered by the Canadian Hydrogen Intensity Mapping Experiment (CHIME), a radio telescope located at Dominion Radio Astrophysical Observatory in British Columbia
  • A NASA-funded project called Survey for Transient Astronomical Radio Emission 2 (STARE2) also detected the radio burst seen by CHIME.

So what is an FRB?

  • The first FRB was discovered in 2007, since when scientists have been working towards finding the source of their origin.
  • FRBs are bright bursts of radio waves (radio waves can be produced by astronomical objects with changing magnetic fields) whose durations lie in the millisecond-scale, because of which it is difficult to detect them and determine their position in the sky.

What is the origin of the FRB detected in April?

  • The source of the FRB detected in April in the Milky Way is a very powerful magnetic neutron star, referred to as a magnetar, called SGR 1935+2154 or SGR 1935.
  • It is located in the constellation Vulpecula and is estimated to be between 14,000-41,000 light-years away.
  • The FRB was part of one of the magnetar’s most prolific flare-ups, with the X-ray bursts lasting less than a second.
  • The radio burst, on the other hand, lasted for a thousandth of a second and was thousands of times brighter than any other radio emissions from magnetars seen in the Milky Way previously.
  • It is possible that the FRB-associated burst was exceptional because it likely occurred at or close to the magnetar’s magnetic pole.
  • This flare-up, which lasted for hours, was picked up by NASA’s Fermi Gamma-ray Space telescope and NASA’s Neutron star Interior Composition Explorer (NICER), which is an X-ray telescope mounted on the International Space Station.

What is a magnetar?

  • A magnetar is a neutron star, “the crushed, city-size remains of a star many times more massive than our Sun.”
  • The magnetic field of such a star is very powerful, which can be over 10 trillion times stronger than a refrigerator magnet and up to a thousand times stronger than a typical neutron star’s.
  • Neutron stars are formed when the core of a massive star undergoes gravitational collapse when it reaches the end of its life.
  • This results in the matter being so tightly packed that even a sugar-cube sized amount of material taken from such a star weighs more than 1 billion tons.
  • Magnetars are a subclass of these neutrons and occasionally release flares with more energy in a fraction of a second than the Sun is capable of emitting in tens of thousands of years.
  • In the case of SGR 1935, the X-ray portion of the simultaneous bursts it released in April carried as much energy as the Sun produces in a month, assuming that the magnetar lies towards the nearer end of its distance range.

Why is this observation significant?

  • Until now, there were various theories that tried to explain what the possible sources of an FRB could be.
  • One of the sources proposed by the theories has been magnetars.
  • But before April this year, scientists did not have any evidence to show that FRBs could be blasted out of a magnetar. Therefore, the observation is especially significant.