My primary research interest is circumstellar debris discs as evidence of planetary systems around mature, main-sequence stars.
Debris discs are the tenuous, dusty remnants of the gas-rich, primordial protoplanetary discs that surround stars during their formation and within which planetary systems like our own are created. They are composed of rocky and icy bodies ranging from micron-sized dust grains to kilometre-sized planetesimals (asteroids and comets). We most commonly observe these systems as an infrared excess at mid- and far-infrared wavelengths produced by thermal emission from small dust grains produced in collisions between larger, unseen planetesimals, but have also observed them at optical and near-infrared wavelengths by the light they scatter from their host star. Currently, we have identifed that around 20 +/- 2 % of nearby sun-like stars have an excess consistent with the presence of debris.
Under the core accretion theory of planet formation, dust grains present in a primordial protoplanetary disc grows through collisions into larger bodies, becoming pebbles, boulders and eventually planetesimals. It is these planetesimals that constitute the building blocks of planets. We might therefore surmise that the presence (and properties) of dusty debris and planets around another star to be correlated. Indeed, we find a higher incidence of planets around systems with debris and have further identified an anti-correlation between planet mass and debris disc brightness.
As an easily visible remnant of the planet formation process, a debris disc is therefore an ideal marker of a planetary system existing around another star. For sun-like stars, these planetary systems represent alternative outcomes of the same planet formation process that produced our own solar system with its two debris belts (the Asteroid belt and Edgeworth-Kuiper belt) and eight planets. By studying such systems in detail we thus obtain an understanding of the formation timescales, range of outcomes, and incidence of planetary systems like our own.