Exoplanet Science lies at the heart of the PLATO mission, in particular the science of transiting exoplanets. By searching for the signatures of planets that pass in front of their host stars, PLATO will discover thousands of new planetary systems.
(Exoplanet Science work breakdown - click to enlarge)
During the development phase of the mission, the Exoplanet Science section of the PSM will work to define and optimise the detection, confirmation, and modelling procedures and algorithms that will be used during the operational phases of the mission. The specifications provided by the PSM will then be implemented by the PLATO Data Centre.
PLATO's exoplanet discoveries will, in almost all cases, rely heavily on an extensive system of ground observations. It is therefore important that this branch of the PSM also develops specific techniques for ranking exoplanet candidates, to allow the Follow-Up program to be as efficient as possible. To reach the aims of the mission we must also take, and refine, our results using information gained from analysis of the host star by techniques developed within the Stellar Science area.
In particular, the Exoplanet Science branch of the PSM will investigate the following:
- Techniques for filtering noise from the data. This means astrophysical noise (e.g. starspots etc.), as well as residual systematic noise arising from the telescopes and instruments.
- Transit detection algorithms. There has been rapid progress in this area, and much has been learnt from previous ground and space based surveys. However, it is important to simulate the performance of the various techniques when applied to the particular design of the PLATO instruments. The reliability of single transit detection also has to be proven, and it is important to fully understand the implications of stellar binarity (or multiplicity) for transit detection; these aspects will likely require new tools to be developed.
- What can be learnt from non-transiting systems that are close enough to display orbital phase variation? Simple scaling laws suggest that small planets would be numerous, and may have detectable signals.
- Planet detection via methods other than transits. It has been demonstrated that timing information derived through other techniques (e.g. pulsation analysis) can be a powerful way of detecting planetary bodies in systems that could not be searched by the usual methods (e.g. white dwarfs). Examining the parameter space of stellar hosts over which these, and other, timing methods can give useful results will have implications for target and field selection.
- Target ranking. The use of centroid shifts during the transit, and other astrophysical mimics, as a false positive discriminator will be investigated. It is vital robust procedures to statistically rank the candidates are developed, and supplied as useable algorithms. Without this the radial velocity follow-up campaign will not be tractable.
- Optimization of transit fitting techniques. Different techniques are commonly used for different types of star and planet; these will be critically examined in light of commonly held assumptions (e.g. the small planet approximation). Related to this is the derivation of sufficiently accurate orbital parameters. For both of these subjects, the PSM must provide the PDC with a robust algorithm specification.
- The requirement for stellar parameters. Planetary data are usually derived relative to that of the host stars. The stellar parameters will be derived from within the Stellar Science work packages, and integrated into the exoplanet processing.
Two of the branches of Exoplanet science, Specification of Planet Detection Tools (WP112) and PLATO Interpretation Specific Science (WP116), have additional sub-branches. These can been seen in the following diagrams (click to enlarge).