ISRO՚s AstroSat for First Time Accomplishes X-Ray Polarization

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AstroSat accomplished the 18-month-long task of measuring X-ray polarization of Crab pulsar in the Taurus constellation for the first time, marking a new era in the country՚s space program.

Pulsar Neutron Star
  • Indian Space Research Organisation (ISRO) launched its first dedicated multi-wavelength space observatory - AstroSat - in Spetember 2015.
  • The observatory has accomplished the extremely strenuous job of X-ray polarisation.
  • The polarization challenges prevailing theories of high-energy radiation from pulsars
  • Indian astronomers documented their results of the study ‘Nature Astronomy’ .
  • They measured the variations of polarization as the highly magnetized neutron star called pulsar spins around 30 times every second.

What is a Pulsar?

  • A pulsar is a rotating neutron star or white dwarf, which emits electromagnetic radiation.
  • The celestial body made up on neutrons and rotates 30 times per second.
  • Although tiny in size, pulsars have much more than entire Sun, and hence are known as compact objects.
  • An extremely large mass condensed in a very small volume makes them have extremely strong gravitational and magnetic fields, both approximately trillion times that on the Earth.
  • Sources of intense X-ray radiation carrying vital information to understand them and the physical processes responsible for the radiation.
Pulsar Neutron Star Image

What is Taurus?

Taurus is the second astrological sign in the present zodiac spaning the 30th -60th degree of the zodiac.

Who Was Involved?

  • Scientists and astronomers from the country՚s top scientific institutes:
  • Tata Institute of Fundamental Research (TIFR) , Mumbai
  • Vikram Sarabhai Space Centre, Thiruvananthapuram
  • ISRO Satellite Centre (ISAC) , Bengaluru
  • The Inter-University Centre for Astronomy and Astrophysics (IUCAA) , Pune
  • Physical Research Laboratory (PRL) , Ahmedabad.

Why is the Discovery Important?

  • The discovery challenges theories of high-energy X-ray emission from pulsars.
  • Astronomers had already studied various properties of this radiation to get complete picture of compact objects, however they were missing information about the elusive properties of X-rays known as polarization.
  • Indian scientists using data from the CZT Imager performed most sensitive measurement of X-ray polarization of the Crab pulsar, which is the main energy source of the nebula
  • Measurements also included polarization properties at different rotation phases of the pulsar- team had to observe the Crab pulsar many times and combine data of months given its small rotation period.
  • To get microsecond accuracy for combining data, the AstroSat team used one of the world՚s best radio telescopes - the Indian Giant Meter-wave Radio Telescope (GMRT) , at Khodad near Pune.

Details of AstroSat

Astrosat Instrument Configuration
  • It is 1,513 kg space observatory built at a cost of ₹ 180 crore
  • Only observatory with five scientific instruments to study celestial objects simultaneously at optical, ultraviolet and x-ray wavebands.
  • Instruments are soft x-ray telescope, an ultraviolet imaging telescope, an imager, and a scanning sky monitor.
  • The landmark measurement was done using satellite՚s CZT (Cadmium-Zinc-Telluride) imaging instrument.

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