IAS Gyan

Daily News Analysis

WHITE DWARF            

24th November, 2021 Science and Technology

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  • A white dwarf star that completes a full rotation once every 25 seconds is the fastest spinning confirmed white dwarf, according to a team of astronomers..



  • They have shown that it is an extremely rare example of a magnetic propeller system.
  • This particular star, named LAMOST J024048.51+195226.9 — or J0240+1952 —is the size of the Earth but is least 200,000 times more massive.
  • It is part of a binary star system; its immense gravity is pulling material from its larger companion star in the form of plasma and flinging it into space at around 3,000 kilometres per second.
  • It is only the second magnetic propeller white dwarf to have been identified in over 70 years.
  • One rotation of the planet Earth takes 24 hours, while the equivalent on J0240+1952 is a mere 25 seconds.


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 then cools down over the next billion years or so.
  • Many nearby, young white dwarfs have been detected as sources of soft, or lower-energy, X-rays.
  • Recently, soft X-ray and extreme ultraviolet observations have become a powerful tool in the study the composition and structure of the thin atmosphere of these stars.
  • A typical white dwarf is half as massive as the Sun, yet only slightly bigger than Earth.
  • An Earth-sized white dwarf has a density of 1 x 109 kg/m3.
  • Earth itself has an average density of only 5.4 x 103 kg/m3.
  • That means a white dwarf is 200,000 times as dense.
  • This makes white dwarfs one of the densest collections of matter, surpassed only by neutron stars.

Note: A typical white dwarf is half the size of our Sun and has a surface gravity 100,000 times that of Earth. Using the Hubble Space telescope and Transiting Exoplanet Survey Satellite (TESS), astronomers have identified several white dwarfs over the years.



  • Usually, white dwarfs are composed of carbon and oxygen (CO white dwarf).
  • Neon Magnesium Helium white dwarf may also form.