Evaporation and accretion of extrasolar comets following white dwarf kicks

Nicholas Stone, Brian D. Metzger, Abraham Loeb

Research output: Contribution to journalArticlepeer-review

Abstract

Several lines of observational evidence suggest that white dwarfs receive small birth kicks due to anisotropic mass-loss. If other stars possess extrasolar analogues to the Solar Oort cloud, the orbits of comets in such clouds will be scrambled by white dwarf natal kicks. Although most comets will be unbound, some will be placed on low angular momentum orbits vulnerable to sublimation or tidal disruption. The dusty debris from these comets will manifest itself as an IR excess temporarily visible around newborn white dwarfs; examples of such discs may already have been seen in the Helix Nebula, and around several other young white dwarfs. Future observations with the James Webb Space Telescope may distinguish this hypothesis from alternatives such as a dynamically excited Kuiper Belt analogue. Although competing hypotheses exist, the observation that ≳15 per cent of young white dwarfs possess such discs, if interpreted as indeed being cometary in origin, provides indirect evidence that low-mass gas giants (thought necessary to produce an Oort cloud) are common in the outer regions of extrasolar planetary systems. Hydrogen abundances in the atmospheres of older white dwarfs can, if sufficiently low, also be used to place constraints on the joint parameter space of natal kicks and exo-Oort cloud models.

Original languageAmerican English
Pages (from-to)188-206
Number of pages19
JournalMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume448
Issue number1
DOIs
StatePublished - 21 Mar 2015
Externally publishedYes

Keywords

  • Accretion
  • Accretion discs
  • Comets: general
  • Infrared: stars
  • White dwarfs

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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