WORLD


This is the way the world ends: Planets turned to dust devoured by a white dwarf star offer a glimpse of our own apocalypse

Baku, May 8 (AzerTAc). The shattered remains of planets that bear a striking resemblance to our own Earth have been found around white dwarf stars - offering a vision of what will one day happen to our planet.
University of Warwick astrophysicists found four white dwarves surrounded by the dust of shattered planets.
White dwarfs are the final stage of life of stars like our Sun - once the thermonuclear furnace inside a star 'burns out'.
Using the Hubble Space Telescope to carry out the biggest survey to date of the chemical composition of the atmospheres of white dwarf stars, the researchers found that the most frequently occurring elements in the dust around these four white dwarfs were oxygen, magnesium, iron and silicon -- the four elements that make up roughly 93 percent of the Earth.
It's evidence that the small, dense stars are surrounded by the 'corpses' of worlds they've 'eaten'.
At least one of the stars is in the process of sucking in the planet's core - rich in iron, nickel and sulphur - at a rate of around a million kilos a second. However an even more significant observation was that this material also contained an extremely low proportion of carbon, which matched very closely that of the Earth and the other rocky planets orbiting closest to our own Sun.
This is the first time that such low proportions of carbon have been measured in the atmospheres of white dwarf stars polluted by debris.
This clear evidence that these stars once had at least one rocky exoplanet which they have now destroyed, the observations must also pinpoint the last phase of the death of these worlds.
The atmosphere of a white dwarf is made up of hydrogen and/or helium, so any heavy elements that come into their atmosphere are dragged downwards to their core and out of sight within a matter of days by the dwarf’s high gravity.
Given this, the astronomers must literally be observing the final phase of the death of these worlds as the material rains down on the stars at rates of up to 1 million kilograms every second.
Not only is this clear evidence that these stars once had rocky exoplanetary bodies which have now been destroyed, the observations of one particular white dwarf, PG0843+516, may also tell the story of the destruction of these worlds.
This star stood out from the rest owing to the relative overabundance of the elements iron, nickel and sulphur in the dust found in its atmosphere. Iron and nickel are found in the cores of terrestrial planets, as they sink to the center owing to the pull of gravity during planetary formation, and so does sulphur thanks to its chemical affinity to iron.
The University of Warwick led team surveyed more than 80 white dwarfs within a few hundred light-years of the Sun, using the Cosmic Origins Spectrograph onboard the Hubble Space Telescope
 

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