Hungry White Dwarfs

Astronomers have found four white dwarf stars they believe to be in the process of  devouring planets similar to Earth.  The evidence for such an extraordinary conclusion lies in the composition of the stars' atmospheres.

Usually the atmosphere of a white dwarf is almost completely made up of hydrogen and helium.  The composition of the atmospheres of the four under study, however, include magnesium, oxygen, iron, and silicon-- the four most common elements in Earth's makeup.  So, astronomers theorize the stars are absorbing terrestrial-type planets that once orbited them.

White dwarfs are the final life stage for stars like the Sun.  As they begin to run low on their nuclear fuels, such stars first swell inro red giants, then implode into white dwarfs.  That dying process, as you might imagine, is not kind to planets orbiting close to the stars.  When the Sun goes through it, for example, Mercury and Venus will be swallowed up, Earth may or may not be, and the changing gravitationnal environment of the system will throw the outer planets into disarray.