Circumstellar Debris and Pollution at White Dwarf Stars

TL;DR

This review discusses the evidence for circumstellar debris disks around white dwarfs, their origins from planetary systems, and how they reveal the composition and evolution of exoplanetary remnants.

Contribution

It synthesizes observational and theoretical evidence for planetary debris disks around white dwarfs and their role in understanding exoplanetary system evolution.

Findings

Disks are within the stellar radii, formed during the white dwarf phase.

Heavy elements in atmospheres indicate ongoing accretion from debris.

Most white dwarfs host remnants of planetary systems.

Abstract

Circumstellar disks of planetary debris are now known or suspected to closely orbit hundreds of white dwarf stars. To date, both data and theory support disks that are entirely contained within the preceding giant stellar radii, and hence must have been produced during the white dwarf phase. This picture is strengthened by the signature of material falling onto the pristine stellar surfaces; disks are always detected together with atmospheric heavy elements. The physical link between this debris and the white dwarf host abundances enables unique insight into the bulk chemistry of extrasolar planetary systems via their remnants. This review summarizes the body of evidence supporting dynamically active planetary systems at a large fraction of all white dwarfs, the remnants of first generation, main-sequence planetary systems, and hence provide insight into initial conditions as well as long-term dynamics and evolution.