Daily Current Affairs for 7th December 2019

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Why planet orbiting white dwarf star is a breakthrough discovery

GS Paper III

Topic: Science and Technology- developments and their applications and effects in everyday life Achievements of Indians in science & technology

Prelims: White dwarf

Mains: What are white dwarf planets and their origin?

What’s the News?

  • The first evidence of a giant planet orbiting a dead white dwarf star has been found in the form of a disc of gas formed from its evaporating atmosphere.

The discovery:

  • The Neptune-like planet orbits a star a quarter of its size about once every ten days, leaving a comet-like tail of gas comprised of hydrogen, oxygen and sulphur in its wake.
  • It is the first evidence of a giant planet orbiting a white dwarf star and suggests that there could be many more planets around such stars waiting to be discovered.
  • Until now, there has never been evidence of a planet that has survived a star’s transition to a white dwarf.
  • Using the Very Large Telescope of the European Southern Observatory in Chile to obtain more observations of this star, they found that the shapes of the hydrogen, oxygen and sulphur features are typical indicators of a ring of gas.

Significance of discovery:

  • This discovery is major progress because over the past two decades we had growing evidence that planetary systems survive into the white dwarf stage.
  • Once our own sun runs out of fuel in about 4.5 billion years it will shed its outer layers, destroying Mercury, Venus, and probably the Earth, and eventually expose the burnt-out core — the white dwarf.
  • The astronomers argue that this planetary evaporation and subsequent accretion by young white dwarfs is probably a relatively common process and that it might open a new window towards studying the chemical composition of the atmospheres of extrasolar gas giant planets.


  • When a Sun-like star runs out of fuel, it swells into a red giant, ejects at least half of its mass, and leaves behind a very hot white dwarf.

Features of white debris:

  • White dwarfs slowly cool as they age, and Debes’ team calculated J0207 is about 3 billion years old based on a temperature just over 10,500 degrees Fahrenheit (5,800 degrees Celsius).
  • A strong infrared signal picked up by NASA’s Wide-field Infrared Survey Explorer (WISE) mission – which mapped the entire sky in infrared light – suggested the presence of dust, making J0207 the oldest and coldest white dwarf with dust yet known.

White debris origin:

  • Over the course of the star’s giant phase, planets and asteroids close to the star become engulfed and incinerated. Planets and asteroids farther away survive, but move outward as their orbits expand. That’s because when the star loses mass, its gravitational influence on surrounding objects is greatly reduced.
  • Scientists think the dust around white debris may arise from distant asteroids and comets kicked closer to the star by gravitational interactions with displaced planets.
  • As these small bodies approach the white dwarf, the stars strong gravity tears them apart in a process called tidal disruption. The debris forms a ring of dust that will slowly spiral down onto the surface of the star.

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