Planetesimals are, by number, the overwhelming component of the proto-planetary disks that surround young stars. Besides their fundamental role as the building blocks of planets they are, as well, expected to play other, no minor, tasks: i) when delivered from beyond the ice-line and impacting in rocky planet surfaces could fill them with their water content and possibly help build their atmospheres; ii) they are responsible for the exocometary activity observed in several late type main sequence stars; iii) they can replenish with gas debris disks, and iv) they cause metal pollution into the surfaces of white dwarfs and allow us to determine the planetary composition in a novel manner.
A significant amount of planetesimals initially in proto-planetary disks are expected to be released into interstellar space, and even a yet unknown fraction is possibly formed orbiting giant evolved stars and ejected as well. In fact, in the past our own asteroid and Kuiper Belts were depleted below their primordial mass by scattering events as the recent discoveries of two interstellar visitors to our Solar System, namely 1I/'Oumuamua (asteroid) and 2I/Borisov (comet) corroborates. This is supposed to be a common phenomenon in stars, the details of which however, are far from being fully understood.
Within this project, "Big problems for small bodies: DISrupting COmetary BOdies and asteroids using Large Objects" (DISCOBOLO) we attempt to tackle problems that underline the importance and role of minor bodies, comets and asteroids, by studying a variety of physical processes -prevalence, ejections, dynamics, chemistry, accretion...- in the environment of stars at different evolutionary stages. The efforts of the team will concentrate in novel approaches to the theoretical understanding of such objects, and on the study of their observational properties.
The detectability of exocometary material around main-sequence stars, and its prevalence, will be assessed, following up previous work by our group on the circumstellar environment of A-type stars, also investigating why the detection of such bodies around cooler, late-type stars, remains elusive. Planet detection around Red Giants, a line also in progress, will continue with the aim of determining the frequency of evolved stars with planets -and brown dwarfs- and their mass distribution, and to provide a wealth of planetary and brown dwarf discoveries, setting stringent constraints to theoretical studies.
Theoretically, we aim to explore the influence of small bodies on planetary evolution and chemistry by studying the rates of their impacts on planet surfaces and the mechanisms by which they take place. Furthermore, we will quantify how gravitational perturbations by large bodies -planets and stars- are expected to disrupt small bodies (either by interactions with planets or resonances) and as a result a significant fraction of planetesimals in disks around evolved stars are released into interstellar space.
The project is demanding and ambitious, but the research team we have gathered, composed of theoreticians, observers and specialists in stars at different evolutionary stages and their peculiarities, guarantees the success of the objectives we detail in the proposal. All this has a clear influence in astrobiology processes including water delivery, atmospheric composition, and the formation and evolution of planetary systems.
