We develop a semi-analytical model for computing planetary system formation with the aim of explaining the observed diversity of planetary systems architectures and relate this primordial diversity with the initial properties of the disc where they were born. We adopt different initial conditions based on recent results in protoplanetary discs observations, to generate a variety of planetary systems and analyze them statistically. We explore the relevance of the mass and size of the disc, its metallicity, the mass of the central star and the time-scale of gaseous disc dissipation, in defining the architecture of the planetary system. We also test different values of some key parameters of our model, to find out which factors best reproduce the diverse sample of observed planetary systems. According to this, we predict which systems are the most common in the solar neighbourhood. Our results show that planetary systems with only terrestrial planets are the most common, being the only planetary systems formed when considering low metallicity discs and which also represent the best environment for the developing of rocky, potentially habitable planets. We also found that planetary systems like our own are not rare in the solar neighbourhood, being its formation favoured in massive discs where there is not a large accumulation of solids in the inner region of the disc. Regarding the planetary systems that harbor hot and warm Jupiter planets, we found that this systems are born in very massive, metal-rich discs. Also a fast migration rate is required in order to form these systems. According to our results, most of the hot and warm Jupiter systems are composed by only one giant planet, which is also a tendency of the current observational data.
Small bodies, the unaccreted leftovers of planetary formation, are often mistaken for the leftovers of planetary science in the sense that they are everything else after the planets and their satellites (or sometimes just their regular satellites) are accounted for. This mistaken view elides the great diversity of compositions, histories, and present-day conditions and processes found in the small bodies, and the interdisciplinary nature of their study. Understanding small bodies is critical to planetary science as a field, and we urge planetary scientists and our decision makers to continue t…
Star compositions are essential for examining densities and compositional ranges of rocky exoplanets, testing their similarity to Earth. Stellar elemental abundances and planetary orbital data show that of the ~5000 known minerals, exoplanetary silicate mantles will contain mostly olivine, orthopyroxene, and clinopyroxene, $\pm$ quartz, and magnesiuwustite at the extremes; wholly exotic mineralogies are likely absent. Understanding these exotic geological systems requires a better marriage of geological insights to astronomical data. The study of exoplanets is like a mirror, reflecting our inc…
This chapter of the Planetary Exploration Horizon 2061 Report reviews the way the six key questions about planetary systems, from their origins to the way they work and their habitability, identified in chapter 1, can be addressed by means of solar system exploration, and how one can find partial answers to these six questions by flying to the different provinces to the solar system: terrestrial planets, giant planets, small bodies, and up to its interface with the local interstellar medium. It derives from this analysis a synthetic description of the most important space observations to be pe…
The coupled interior-atmosphere system of terrestrial exoplanets remains poorly understood. Exoplanets show a wide variety of sizes, densities, surface temperatures, and interior structures, with important knock-on effects for this coupled system. Many exoplanets are predicted to have a "stagnant lid" at the surface, with a rigid stationary crust, sluggish mantle convection, and only minor volcanism. However, if exoplanets have Earth-like plate tectonics, which involves several discrete, slowly moving plates and vigorous tectono-magmatic activity, then this may be critical for planetary habita…
The planetary systems detected so far already exhibit a wide diversity of architectures, and various methods are proposed to study quantitatively this diversity. Straightforward ways to quantify the difference between two systems and more generally, two sets of multiplanetary systems, are useful tools in the study of this diversity. In this work we present a novel approach, using a Weighted extension of the Energy Distance (WED) metric, to quantify the difference between planetary systems on the logarithmic period-radius plane. We demonstrate the use of this metric and its relation to previous…
A comprehensive study of the relations between the properties of planetary systems and the chemical compositions of their host stars
Universidade Federal do Rio de Janeiro（里约热内卢联邦大学）；Observatório Nacional（国家天文台）；Universidade Federal de Sergipe（塞尔希培联邦大学）；Steward Observatory, University of Arizona（亚利桑那大学斯图尔德天文台）
The final orbital configuration of a planetary system is shaped by both its early star-disk environment and late-stage gravitational interactions. Assessing the relative importance of each of these factors is not straightforward due to the observed diversity of planetary systems compounded by observational biases. Our goal is to understand how a planetary system may change when planetesimal accretion and planet migrations stop and secular gravitational effects take over. Our approach starts with a novel classification of planetary systems based on their orbital architecture, validated using Ap…
Because of the diversity of stellar masses and orbital sizes of binary systems, and the complex interaction between star-star, star-planet and planet-planet, it has been difficult to fully characterize the planetary systems associated with binary systems. Here, we report high-precision astrometric observations of the low-mass binary system GJ 896AB, revealing the presence of a Jupiter-like planetary companion (GJ 896Ab). The planetary companion is associated to the main star GJ 896A, with an estimated mass of 2.3 Jupiter masses and an orbit period of 284.4 days. A simultaneous analysis of the …
The diversity in mass and composition of planetary atmospheres stems from the different building blocks present in protoplanetary discs and from the different physical and chemical processes that these experience during the planetary assembly and evolution. This review aims to summarise, in a nutshell, the key concepts and processes operating during planet formation, with a focus on the delivery of volatiles to the inner regions of the planetary system.
Pairwise collisions between terrestrial embryos are the dominant means of accretion during the last stage of planet formation. Hence, their realistic treatment in N-body studies is critical to accurately model the formation of terrestrial planets and to develop interpretations of telescopic and spacecraft observations. In this work, we compare the effects of two collision prescriptions on the core-mantle differentiation of terrestrial planets: a model in which collisions are always completely accretionary (``perfect merging'') and a more realistic model based on neural networks that has been t…
Exoplanets display incredible diversity, from planetary system architectures around Sun-like stars that are very different to our Solar System, to planets orbiting post-main sequence stars or stellar remnants. Recently the B-star Exoplanet Abundance STudy (BEAST) reported the discovery of at least two super-Jovian planets orbiting massive stars in the Sco Cen OB association. Whilst such massive stars do have Keplerian discs, it is hard to envisage gas giant planets being able to form in such hostile environments. We use N-body simulations of star-forming regions to show that these systems can …
Exoplanetary science continues to excite and surprise with its rich diversity. We discuss here some key aspects potentially influencing the range of exoplanetary terrestrial-type atmospheres which could exist in nature. We are motivated by newly emerging observations, refined approaches to address data degeneracies, improved theories for key processes affecting atmospheric evolution and a new generation of atmospheric models which couple physical processes from the deep interior through to the exosphere and consider the planetary-star system as a whole. Using the Solar System as our guide we f…
The diversity of planetary systems that have been discovered are revealing the plethora of possible architectures, providing insights into planet formation and evolution. They also increase our understanding of system parameters that may affect planetary habitability, and how such conditions are influenced by initial conditions. The AU~Mic system is unique among known planetary systems in that it is a nearby, young, multi-planet transiting system. Such a young and well characterized system provides an opportunity to study orbital dynamical and habitability studies for planets in the very early…
Previous studies using Kepler data suggest that planets orbiting the same star tend to have similar sizes. However, due to the faintness of the stars, only a few of the planets were also detected with radial velocity follow-ups, and therefore the planetary masses were mostly unknown. It therefore yet to be determined whether planetary systems indeed behave as "peas in a pod". Follow-up programs of TESS targets significantly increased the number of confirmed planets with mass measurements, allowing for a more detailed statistical analysis of multi-planet systems. In this work we explore the sim…
Despite the discovery of thousands of exoplanets in recent years, the number of known exoplanets in star clusters remains tiny. This may be a consequence of close stellar encounters perturbing the dynamical evolution of planetary systems in these clusters. Here, we present the results from direct $N$-body simulations of multiplanetary systems embedded in star clusters containing $N = 8k, 16k, 32k$, and $64k$ stars. The planetary systems, which consist of the four Solar system giant planets Jupiter, Saturn, Uranus, and Neptune, are initialized in different orbital configurations, to study the e…
Today, we know ~4330 exoplanets orbiting their host stars in ~3200 planetary systems. The diversity of these exoplanets is large, and none of the known exoplanets is a twin to any of the solar system planets, nor is any of the known extrasolar planetary systems a twin of the solar system. Such diversity on many scales and structural levels requires fundamental theoretical approaches. Large efforts are underway to develop individual aspects of exoplanet sciences, like exoplanet atmospheres, cloud formation, disk chemistry, planet system dynamics, mantle convection, mass loss of planetary atmosp…
In the general classical picture of pebble-based core growth, planetary cores grow by accretion of single pebble species. The growing planet may reach the so-called pebble isolation mass, at which it induces a pressure bump that blocks inward drifting pebbles exterior to its orbit, thereby stalling core growth by pebble accretion. In recent hydrodynamic simulations, pebble filtration by the pressure bump depends on several parameters including core mass, disc structure, turbulent viscosity and pebble size. We investigated how accretion of multiple, instead of single, pebble species affects cor…
In the Solar System short-lived radioisotopes, such as 26Al, played a crucial role during the formation planetary bodies by providing a significant additional source of heat. Notably, this led to early and large-scale melting and iron core formation in planetesimals and their loss of volatile elements, such as hydrogen and carbon. In the context exoplanetary systems, therefore, the prevalence of short-lived radioisotopes is key to interpreting the observed bulk volatile budget and atmospheric diversity among low-mass exoplanets. White dwarfs that have accreted planetary material provide a uniq…
Giant planets can interact with multiple and chemically diverse environments in protoplanetary discs while they form and migrate to their final orbits. The way this interaction affects the accretion of gas and solids shapes the chemical composition of the planets and of their atmospheres. Here we investigate the effects of different chemical structures of the host protoplanetary disc on the planetary composition. We consider both scenarios of molecular (inheritance from the pre-stellar cloud) and atomic (complete chemical reset) initial abundances in the disc. We focus on four elemental tracer…
