1. Department of Astronomy, University of Florida, Gainesville, Florida 32611, USA
2. Gemini Observatory Northern Operations Center, 670 N. A'ohoku Place, Hilo, Hawaii 96720, USA
3. UK Astronomy Technology Centre, Royal Observatory, Edinburgh EH9 3HJ, UK
4. Gemini Observatory Southern Operations Center, c/o AURA, Casilla 603, La Serena, Chile
5. Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, Casilla 603, La Serena, Chile

Correspondence to: Charles M. Telesco¹ Correspondence and requests for materials should be addressed to C.M.T. (Email: telesco@astro.ufl.edu).

When viewed in optical starlight scattered by dust, the nearly edge-on debris disk surrounding the A5V star Pictoris (distance 19.3 pc; ref. 1) extends farther than 1,450 au from the star². 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^{3, 4}, perhaps resulting in both the observed tilt of 4.6 degrees relative to the large-scale main disk^{5, 6} and the partial clearing of the innermost dust^{7, 8, 9}. A peculiarity of the central disk (also possibly related to the presence of planets) is the asymmetry in the brightness of the 'wings'^{9, 10}, in which the southwestern wing is brighter and more extended at 12 m 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.

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