Young white dwarfs have to cool first before they get disc of material around them

When a star like our Sun burns all the hydrogen and helium in its disposal, it becomes a white dwarf - small, hot and dense core of the star that was. Around this core remains the matter from the outer layers of the progenitor star. These layers can form disk of material around the white dwarf, but only after the star cools.

Summary

  
Astronomers sometimes see discs around white dwarfs.
  
New study suggests, that these structures can form only after the dense remnant of a star cools enough to allow condensation of matter in its surroundings.