Millimetre observations of Pleiades stars: a lack of solar-analogue planetesimal discs at 100 Myr?

Solar analogues approximately 100 Myr old may have dusty debris from collisions within evolving cometary belts, and such remnant discs might also be associated with earlier stellarspin braking. We observed at 1.2 mm wavelength a sample of 17 fast and slow rotators, mostly single K dwarfs, in the 100 Myr Pleiades cluster. No dust was detected for individual stars or the ensemble, so there are no cold massive debris discs nor any discernible relation of such distant material to stellar spin. The net limits from these data and our earlier far-infrared results imply that the typical Pleiades G/K dwarf has a relative disc-to-star luminosity 2 × 10−4. Collisional evolution models have predicted greater luminosities at the 108 yr epoch, for debris discs evolving out of a proto-solar nebula. This suggests that substantial primordial discs such as that of the Sun are not the norm amongst young solar analogues, or that dynamical interactions with giant planets can remove much of the comet belt by as early as 100 Myr.