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Fast Radio Burst (FRB)

Posted on June 10, 2022 by admin1  900

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Recently, astronomers have reported a Fast Radio Burst (FRB) whose characteristics are different from almost all other FRBs previously detected, except one.

Key Findings

  • One of the best-known fast radio bursts is FRB20180916B. This FRB was discovered in 2018 and is only 500 million light-years away from us in another galaxy.
    • Repetition: The FRB is the closest so far and has a burst pattern that repeats every 16 days: four days of bursts, 12 days of relative quiet. That predictability makes it an ideal object for researchers to study.
    • And between bursts, it constantly emits weaker radio waves. 
  • Location: It is co-located with a compact, persistent radio source and associated with a dwarf host galaxy of high specific-star-formation.
  • Only one FRB has been previously observed to behave this way. Called FRB 121102, it was discovered in 2012.
  • The discovery raises new questions about the nature of these mysterious objects and also about their usefulness as tools for studying the nature of intergalactic space. 
  • The scientists used the National Science Foundation’s Karl G Jansky Very Large Array (VLA) and other telescopes to study the object.
  • The astronomers have suggested that there may be two different mechanisms producing FRBs, or that the objects producing them may act differently at different stages. 
    • Among the candidates for the sources of FRBs are the superdense neutron stars left over after a supernova, or magnetars (neutron stars with ultra-strong magnetic fields).
  • The researchers have also theorised that the FRB 190520 may be a newborn. This means it is still surrounded by dense material ejected by the supernova explosion that left behind the neutron star.

Fast Radio Burst (FRB)

  • FRBs are bright flashes (radio Pulses) of light and are super intense, millisecond-long bursts of radio waves produced by unidentified sources in the distant cosmos. 
  • Their origins are unknown, and their appearance is unpredictable.
  • They were first discovered in 2007 when scientists combed through archival pulsar data. 
    • Pulsars refer to spherical, compact objects in the universe, which are about the size of a large city but contain more mass than the sun. 
    • They often look like flickering stars but are not stars.

 

  • Since the first FRB was discovered in 2007, 140 more were discovered until June 2021. 

 

Image Courtesy: Quant 

Significance

  • It can be used to understand the three–dimensional structure of matter in the universe.
  • It will even help to learn about the origin and evolution of the universe.
  • Big questions still remain, and this object is giving us challenging clues about those questions relating to the Universe.

Conclusion

  • The FRB field is moving very fast right now and new discoveries are coming out monthly. 

Magnetar

  • About: 
    • A magnetar is a rare compact type of neutron star teeming with energy and magnetism. 
    • They are relatively rare objects, with only about thirty having been spotted within the Milky Way so far. 
  • Study: 
    • The present magnetar is only the second one to be studied which is located outside the galaxy and is also the furthest, at 13 million light years distance but is the first study to characterise such a flare from such a distant magnetar.
  • How magnetars form
    • During the course of their evolution, massive stars – with masses around 10-25 times the mass of the Sun – eventually collapse and shrink to form very compact objects called neutron stars. 
    • A subset of these neutron stars are the so-called magnetars which possess intense magnetic fields. 
    • These are highly dense and have breathtakingly high rotation speeds – they have rotational periods that can be just 0.3 to 12.0 seconds. 
  • High luminosity:
    • Magnetars have high magnetic fields in the range of 1015 gauss and they emit energy in the range given by luminosities of 1037 – 1040 joules per second. 
    • Compare this to the luminosity of the sun which is in the order of 1026 joules per second – a factor of at least 1011 lower. Further, these magnetars emit violent flares.
  • Energy dissipation:
    • Eruptions in magnetars are believed to be due to instabilities in their magnetosphere, or “starquakes” produced in their crust – a rigid, elastic layer about one kilometre thick. This causes waves in the magnetosphere, and interaction between these waves causes dissipation of energy. 
    • Magnetars are very difficult to observe when they are silent. It is only during a flare that they can be observed, and these flares are so short-lived that it presents a formidable problem. 
  • Cosmic lighthouses:
    • A few magnetars are also pulsars, those celestial lighthouses that sweep the sky with powerful radio beams (and, rarely, beams of visible light too, such as in the case of the Crab Nebula). 
    • Recently, detecting a magnetar that is also a pulsar enabled astronomers to establish an accurate distance to a magnetar for the first time.

Source: IE

 
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