Statistics of Debris Disks
The very presence of debris disks can also yield a significant amount of information, even if those disks are too distant, or too faint to be imaged:
Wyatt, Dent & Greaves (2003) used sub-millimetre photometry of a sample of nearby young (10-170 Myr) stars to show that the dispersal of the massive protoplanetary disks found around younger T Tauri and Herbig AeBe stars must have taken place by 10 Myr. This sets hard constraints on the timescale within which planets can form. Further, none of the three disks that were detected with SCUBA were also detected in the far-infrared by IRAS. This not only implies these disks are cold (<40 K), but also that the 15% fraction of stars with disks which was inferred from IRAS detections may be an underestimate by up to a factor of two.
Greaves & Wyatt (in press) collated published observations debris disks to explore the issue of how disk mass varies with stellar age. They found that disks are found at all stages of a star’s main sequence lifetime, but that disk mass does decrease slightly with age, proportional to t -0.5. They also showed that disks are much more likely to be found around A stars, than G stars, even when the higher luminosity of A stars is taken into account.
Sheret, Dent & Wyatt (2003) presented the results of a SCUBA photometry programme to search for sub-millimetre emission toward nearby stars. Modelling of the resulting Spectral Energy Distributions was able to set constraints on the size distribution and composition of these disks, as well as to estimate the spatial extent of unresolved disks.