The polarimetric dust properties of the debris disc HR4796

Abstract : Debris discs represent the ultimate stage of planetary formation, after the initial gas-rich protoplanetary disc dissipated and potential giant planets have already formed in the system. Infrared observations have shown that at least 20% of main-sequence stars host a dusty debris disc [1], i.e. a massive analog to the Edgeworth-Kuiper belt in the solar system, typically detected at tens to hundreds of astronomical units from their parents stars. Considering the short lifetime of the dust particles compared to the system age, this dust population is believed to originate from collisions of a population of kilometre-sized parent bodies, called planetesimals, reminiscent of Kuiper belt objects or comets in our solar system. Collisions constantly replenish the disc and create smaller and smaller dust particles, until the smallest micron-sized particles leave the system expelled by the radiation pressure of the central star.