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Pulsating White Dwarf

  • IASbaba
  • October 26, 2021
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Pulsating White Dwarf

Part of: Prelims and GS III – Sci and Tech 

Context A team of astronomers, using NASA’s Transiting Exoplanet Survey Satellite (TESS) have reported a unique phenomenon in a white dwarf about 1,400 light years from Earth. 

  • They saw the white dwarf lose its brightness in 30 minutes. 

About white dwarf

  • A white dwarf is what stars like the Sun become after they have exhausted their nuclear fuel. 
  • Near the end of its nuclear burning stage, this type of star expels most of its outer material, creating a planetary nebula. 
  • Only the hot core of the star remains. 
  • This core becomes a very hot white dwarf, with a temperature exceeding 100,000 Kelvin. 
  • The white dwarf cools down over the next billion years or so.
  • A pulsating white dwarf is a white dwarf star whose luminosity varies due to non-radial gravity wave pulsations within itself. 

It’s switch on and off mode

  • As per scientists,in this system the donor star in orbit around the white dwarf keeps feeding the accretion disk. 
    • An accretion disk is a structure formed by diffuse material in orbital motion around a massive central body. The central body is typically a star.
  • As the accretion disk material slowly sinks closer towards the white dwarf it generally becomes brighter(on mode). 
  • During the ‘on’ mode, the white dwarf feeds off the accretion disk as it normally would. 
  • Suddenly and abruptly the system turns ‘off’ and its brightness plummets.
  • When this happens the magnetic field is spinning so rapidly that a centrifugal barrier stops the fuel from the accretion disk constantly falling on to the white dwarf.
  • The new discovery will help the astronomers understand the physics behind accretion – how black holes and neutron stars feed material from their nearby stars. 

About Transiting Exoplanet Survey Satellite (TESS)

  • TESS  is a space telescope for NASA’s Explorers program, designed to search for exoplanets using the transit method in an area 400 times larger than that covered by the Kepler mission.
  • It was launched in 2018 by Falcon rocket system.
  • Using the Hubble Space telescope and TESS, astronomers have identified several white dwarfs over the years.

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