White dwarfs are ‘heavy metal’ zombie stars endlessly cannibalizing their dead planetary systems

White dwarfs are dense, dead remnants of stars like our Sun that have burned up their nuclear fuel. They account for 97% of stars in the Milky Way.
Scientists have discovered that white dwarfs have layers of “heavy metals” like silicon, magnesium and calcium on their surface, which is puzzling since these elements should sink below the surface.
New research through computer simulations suggests white dwarfs feed on rocky planetary remnants like asteroids and comets that orbit them after receiving a “natal kick” during formation, altering planetary orbits.
The kick causes orbits to become more elongated and aligned, with 40% in retrograde orbits opposing the star’s rotation. Planetesimals within 30 AU are most at risk.


Over 100 million years of simulation, the close-in planetesimals maintained elongated, coinciding orbits and began streaming, allowing for continued long-term feeding of the white dwarf to replenish surface metals.
This helps explain how white dwarfs can maintain heavy metal layers despite the elements sinking – they are constantly harvesting remnants of their dead planetary systems, acting as “zombie stars” that mindlessly consume surrounding materials.

Source: Space

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