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14th of July 2021
Proto-planets and PLATYPUS
by Norfolk et al.
Planets form from the material in molecular clouds left over from the formation of stars. Debris discs are the final stage of protoplanetary disc evolution. The majority of primordial gas has either accreted onto the star or been blown away by stellar winds, and the remaining dust is replenished through ongoing collisions between dust-producing planetesimals, i.e., asteroids and comets. The size distribution of the grains produced by these collisions provides insight into the different physical and dynamical properties of the invisible parent planetesimals. The material properties and collisional models of planetesimals leave their signature on the grain size distribution, which can be traced through the millimetre spectral index. Norfolk et al. present 8.8 mm (33 and 35 GHz) observations of the debris discs in four relatively young debris disc host stars spanning a broad range of stellar luminosities, as part of the PLanetesimals Around TYpical Pre-main seqUence Stars (PLATYPUS) survey. All four targets were detected with a characteristic beam size of 5 arcseconds and a grain size distribution parameter was derived that is consistent with collisional cascade models and theoretical predictions for parent planetesimal bodies.

The images above show the four debris discs detected in the ATCA observations. The synthesized ATCA beam FWHM extent and orientation for each observations is represented by the shaded ellipse in the bottom left of each panel. The contours are ±2-sigma and 3-sigma, with negative contours denoted by dashed lines. The paper will be published in Monthly Notices of the Royal Astronomical Society.

ASKAP Survey Science Projects include WALLABY, EMU, DINGO and POSSUM; QUOKKA is an ATCA survey, and there is a companion LBA project named QUOLL, so PLATYPUS has plenty of good company!

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