'Dead planets around dead stars'

Polluted White Dwarfs

Once a star, similar to our Sun, ceases fusing hydrogen, it will undergo a violent stage of stellar evolution resulting in the production of a small, hot and dense stellar core. This is a white dwarf. It has been demonstrated that although the inner planetary system is engulfed during the red giant stage, the outer planetary system can survive. Evidence for the survival of outer planetary systems to the white dwarf phase comes from observations of planetary material polluting the atmospheres of white dwarfs. At least 30% of white dwarfs have been observed with elements heavier than helium in their atmospheres. The rapid gravitational settling times in comparison to the white dwarf's cooling age implies ongoing accretion from an external reservoir. So we are witnessing exo-planetary destruction in action. These white dwarfs systems with atmospheric pollutants are called polluted white dwarfs.

My Research

  • It is thought that the source of the pollution is tidally disrupted extrasolar planetesimals. I am interested in near and mid infrared observations of the dust around the white dwarfs to search for infrared variability.
  • I am also interested in searching for variability in the metal spectral features in the white dwarf atmospheres.
  • These approaches help us to understand the stages leading up to the planetesimals being engulfed by their host star. This aids the understanding of the end stages of a planetary system.