Mid-infrared images of beta Pictoris and the possible role of planetesimal collisions in the central disk.

When viewed in optical starlight scattered by dust, the nearly edge-on debris disk surrounding the A5V star β Pictoris (distance 19.3 pc; ref. 1) extends farther than 1,450 au from the star. Its large-scale complexity has been well characterized, but the detailed structure of the disk's central ∼200-au region has remained elusive. This region is of special interest, because planets may have formed there during the star's 10–20-million-year lifetime, perhaps resulting in both the observed tilt of 4.6 degrees relative to the large-scale main disk and the partial clearing of the innermost dust. A peculiarity of the central disk (also possibly related to the presence of planets) is the asymmetry in the brightness of the ‘wings’, in which the southwestern wing is brighter and more extended at 12 µm than the northeastern wing. Here we present thermal infrared images of the central disk that imply that the brightness asymmetry results from the presence of a bright clump composed of particles that may differ in size from dust elsewhere in the disk. We suggest that this clump results from the collisional grinding of resonantly trapped planetesimals or the cataclysmic break-up of a planetesimal.

[1]  Michael S. Bessell,et al.  The β Pictoris Moving Group , 2001 .

[2]  E. Becklin,et al.  Resolution of the circumstellar disk of β Pictoris at 10 and 20 µm , 1988, Nature.

[3]  H. Beust,et al.  Cometary-like bodies in the protoplanetary disk aroundβ pictoris , 1994 .

[4]  M. C. Wyatt,et al.  HOW OBSERVATIONS OF CIRCUMSTELLAR DISK ASYMMETRIES CAN REVEAL HIDDEN PLANETS : PERICENTER GLOW AND ITS APPLICATION TO THE HR 4796 DISK , 1999 .

[5]  A. Vidal-Madjar,et al.  The β Pictoris circumstellar disk. VI: Evidence for material falling on to the star , 1988 .

[6]  G. Vogt.  Asteroids, Comets and Meteors , 1996 .

[7]  Mid-infrared images and models of the β Pictoris dust disk ? , 1997 .

[8]  A. Vidal-Madjar,et al.  BETA PICTORIS REVISITED BY HIPPARCOS : STAR PROPERTIES , 1997 .

[9]  Close stellar encounters with planetesimal discs: the dynamics of asymmetry in the β Pictoris system , 2000, astro-ph/0011279.

[10]  M. C. Wyatt,et al.  RESONANT TRAPPING OF PLANETESIMALS BY PLANET MIGRATION: DEBRIS DISK CLUMPS AND VEGA'S SIMILARITY TO THE SOLAR SYSTEM , 2003 .

[11]  Pierre-Olivier Lagage,et al.  Mid-infrared images and models of the beta Pictoris dust disk , 1997 .

[12]  The spatial structure of the beta Pictoris gas disk , 2003, astro-ph/0310146.

[13]  B. Zuckerman,et al.  The First Spatially Resolved Mid-Infrared Spectroscopy of β Pictoris , 2003 .

[14]  C. Dominik,et al.  Age Dependence of the Vega Phenomenon: Theory , 2003, astro-ph/0308364.

[15]  D. Mouillet,et al.  A planet on an inclined orbit as an explanation of the warp in the β Pictoris disc , 1997 .

[16]  The Inner Rings of β Pictoris , 2002, astro-ph/0212081.

[17]  F. C. Witteborn,et al.  Infrared observations and thermal models of the Beta Pictoris disk , 1992 .

[18]  S. Dermott,et al.  A circumsolar ring of asteroidal dust in resonant lock with the Earth , 1994, Nature.

[19]  Collisional processes in extrasolar planetesimal discs – dust clumps in Fomalhaut's debris disc , 2002, astro-ph/0204034.

[20]  S. Kenyon,et al.  Detecting the Dusty Debris of Terrestrial Planet Formation , 2004, astro-ph/0401343.

[21]  Bruce E. Woodgate,et al.  Space Telescope Imaging Spectrograph Coronagraphic Observations of β Pictoris , 2000 .

[22]  Shigeyuki Sako,et al.  An early extrasolar planetary system revealed by planetesimal belts in β Pictoris , 2004, Nature.

[23]  J. Greenberg,et al.  A comet dust model for the beta Pictoris disk , 1998 .

[24]  William K. Hartmann,et al.  Satellite-Sized Planetesimals and Lunar Origin , 1975 .

[25]  P. O. Lagage,et al.  Dust depletion in the inner disk of β Pictoris as a possible indicator of planets , 1994, Nature.