Europlanet Science Congress 2022
Palacio de Congresos de Granada, Spain
18 – 23 September 2022
Europlanet Science Congress 2022
Palacio de Congresos de Granada, Spain
18 September – 23 September 2022
Formation, evolution, and stability of extrasolar systems


Hundreds of planetary systems are currently known. A deep understanding of the architecture of both RV-detected systems and transit-detected systems is essential to probe planetary system formation.

In this session we address the question of the formation, dynamical evolution and stability of planetary systems in a broad sense, including the effects of planet-disc interactions, resonances, high eccentricity migration, binary stars, chaotic dynamics,...

Conveners: Anne-Sophie Libert, Antoine Petit
| Mon, 19 Sep, 10:00–11:30 (CEST), 15:30–17:00 (CEST)|Room Andalucia 3
| Attendance Mon, 19 Sep, 18:45–20:15 (CEST) | Display Mon, 19 Sep, 08:30–Wed, 21 Sep, 11:00|Poster area Level 2

Session assets

Discussion on Slack

Orals: Mon, 19 Sep | Room Andalucia 3

Chairperson: Antoine Petit
Disc and tidal interactions
Philippine Griveaud, Aurélien Crida, and Elena Lega

Planets form in protoplanetary discs and their interactions with the gas give rise to migration. For a long time, discs were believed to have a non-negligible viscosity to justify the high accretion rates of gas onto the central star. However, it has recently been shown observationally and theoretically that protoplanetary discs are probably much less viscous than previously thought. In our study, we use a new paradigm for the theoretical modelling of discs where the accretion onto the central star is done through the superficial layers while the mid-plane has a close to zero viscosity (Lega et al. 2022). In such discs, the migration of a single giant planet differs from the classical Type-II migration regime and depends on the thickness of the accretion layer. It is therefore interesting to consider the migration of a pair of giant planets in this new model. We have started this project, in the simplified framework of 2D hydrodynamical simulations (using the code FARGOCA) with an α viscosity parameter of 10−5 (in the standard Shakura & Sunyaev 1973 viscosity parametrization). We first consider a pair of Jupiter and Saturn mass planets, then extend our study to a wider range of planetary masses.

In classical viscous discs (corresponding to an α=10−3), Jupiter and Saturn systems are most often locked in the 3:2 mean motion resonance and may migrate outwards. Instead in our case (α=10−5), we find that the pair of planets gets locked in the 2:1 resonance and has a stalled or slightly inward migration. We confirmed this result for a range of disc masses and thicknesses as well as different starting positions of Saturn. This result is also independent of the mass of the outer planet. In order to explain our result, we have a used a criterion for resonance crossing based on Batygin, 2015 . Unlike in classical discs, a planet growing and migrating in a low viscosity disc does not reach the migration speed required to cross the 2:1 MMR. The only case in which outward migration is observed, is the "ad-hoc" scenario where Saturn would form inside the 2:1 resonance and get locked in the 3:2. However, owing to the large width of Jupiter's gap, this scenario seems unlikely.

If the Solar System formed from such a low-viscosity disc, this result has strong implications for the Grand Tack and Nice models, which both assume Jupiter and Saturn to be inside the 2:1 resonance. The stalled migration could, however, explain the so called warm-Jupiters population among the detected exoplanets, providing that these are in multi-planet systems. Additionally, we remark that the only system with two giant planets observed in a disc of gas, namely PDS70, occurs to be close to the 2:1 resonance.


Figure 1: Surface density of a 2D simulation after nearly 300 000 years of evolution, displaying Jupiter (filled circle) and Saturn (empty circle) in their common gap. The planets are stably locked in the 2:1 mean motion resonance and are following a very slow inward migration at a speed of one a.u. per million years.



E. Lega et al., “Migration of Jupiter Mass Planets in Discs with Laminar Accretion Flows,” Astronomy & Astrophysics 658 (2022)

Konstantin Batygin, “Capture of Planets into Mean-Motion Resonances and the Origins of Extrasolar Orbital Architectures,” Monthly Notices of the Royal Astronomical Society 451, no. 3 (August 11, 2015)


How to cite: Griveaud, P., Crida, A., and Lega, E.: Minimal viscosity discs lock pairs of giant planets in 2:1 resonance with stalled migration., Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-464,, 2022.

Oliver Schib, Christoph Mordasini, and Ravit Helled

We aim to develop a simple prescription for migration and accretion in 1D disc models, calibrated with results of 3D hydrodynamic simulations [1,2]. Our focus lies on non-self-gravitating discs, but we also discuss to what degree our prescription could be applied when the discs are self-gravitating.

We study migration using torque densities. Our model for the torque density is based on existing fitting formulas, which we subsequently modify to prevent premature gap-opening. At higher planetary masses, we also apply torque densities from hydrodynamic simulations directly to our 1D model [3]. These torque densities allow modelling the orbital evolution of an initially low-mass planet that undergoes runaway-accretion to become a massive planet. The two-way exchange of angular momentum between disc and planet is included. This leads to a self-consistent treatment of gap formation that only relies on directly accessible disc parameters.

We present a formula for Bondi- and Hill- gas accretion in the disc-limited regime. This formula is self-consistent in the sense that mass is removed from the disc in the location from where it is accreted. Fig. 1 shows an exampe of the time evolution of semi-major axis and mass of a growing, migrating planet. Our proposed model "High mass torque" is shown as purple dash-dotted line.

We find that the resulting evolution in mass and semi-major axis in the 1D framework is in good agreement with those from 3D hydrodynamical simulations for a range of parameters.

Our prescription is valuable for simultaneously modelling migration and accretion in 1D-models. We conclude that it is appropriate and beneficial to apply torque densities from hydrodynamic simulations in 1D models, at least in the parameter space we study here. More work is needed to in order to determine whether our approach is also applicable in an even wider parameter space and in situations with more complex disc thermodynamics, or when the disc is self-gravitating.

Fig. 1: Time evolution of an initially low-mass planet (5 Mearth), starting at 5.2 au in a disc with an initial surface density of 100 g cm-2. Left: Semi-major axis. Right: Planetary mass. The figure shows different models for the torque density and the feeding zone radius we studied in [4].

[1] D’Angelo, G. & Lubow, S. H. 2008, Astrophysical Journal, 685, 560
[2] D’Angelo, G. & Lubow, S. H. 2010, Astrophysical Journal, 724, 730
[3] Schib, O., Mordasini, C., Wenger, N., Marleau, G. D., & Helled, R. 2021, Astronomy and Astrophysics, 645, A43
[4] Schib, Mordasini & Helled 2022, Astronomy and Astrophysics accepted

How to cite: Schib, O., Mordasini, C., and Helled, R.: Calibrated Gas Accretion and Orbital Migration of Protoplanets in 1D Disc Models, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-46,, 2022.

Guillem Anglada, Ana K. Diaz-Rodriguez, Guillermo Blázquez-Calero, Mayra Osorio, José F. Gómez, Gary A. Fuller, Robert Estalella, José M. Torrelles, Sylvie Cabrit, Luis F. Rodríguez, Enrique Macías, Carlos Carrasco-González, Luis A. Zapata, Itziar de Gregorio-Monsalvo, and Paul T. P. Ho

The early stages of the formation of binary stellar systems are still rather poorly understood observationally, which contrasts with some significant recent improvements in numerical simulations. We present a comprehensive study with the VLA and ALMA of the close (separation = 90 au) proto-binary system SVS 13. Our very high sensitivity and spatial resolution observations trace the dust as well as the ionized and molecular gas in this system, reaching scales as small as ~10 au. We infer the orbital motion and masses of the two protostars. We image two circumstellar disks and a still-forming circumbinary disk with prominent spiral arms extending ~500 au. We study the 3D kinematics of the system and measure the physical properties of the disks. We also find evidence for variation of chemical properties on scales of a few tens of au. Finally, we will discuss on how the properties of the SVS 13 system compare with those of a few other protobinary systems that have been observed with a similar degree of detail, and with the predictions of numerical simulations. This kind of information provides some clues on the final configuration of planetary systems in binary systems.

ALMA observation of dust in the disks around SVS 13 (credit: A.K. Diaz-Rodriguez, G. Anglada 2022).


Cartoon model of the system. The red-blue colours indicate the motion of the gas. Red – away from us, blue – towards us. The peculiar yin-yang shape results from the combination of infalling and rotation motions (credit: A. K. Diaz-Rodriguez et al. 2022).

How to cite: Anglada, G., Diaz-Rodriguez, A. K., Blázquez-Calero, G., Osorio, M., Gómez, J. F., Fuller, G. A., Estalella, R., Torrelles, J. M., Cabrit, S., Rodríguez, L. F., Macías, E., Carrasco-González, C., Zapata, L. A., de Gregorio-Monsalvo, I., and Ho, P. T. P.: Observing the very early stages of the formation of a circumbinary planetary system in SVS 13, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1031,, 2022.

Nader Haghighipour

The discovery of multi-planet resonant chains such as those in TRAPPIST-1 and Kepler-90, where adjacent planets are in different commensurabilities, has raised questions on the formation of these systems and the reason for the diversity of their resonances. It is widely accepted that these systems formed through the combination of migration and resonance-capture where migrating planets capture each other in resonances. However, this scenario cannot explain why adjacent planets have different period-ratios. The reason is that migrating planets tend to capture each other in the same resonances (e.g., the three giant planets in the four-planet system of GJ 876 are in a 4:2:1 Laplace resonance).

To overcome this difficulty, it has been suggested that the diversity of resonances in resonant-chain systems is a post-capture phenomenon that has roots in the mutual tidal interactions of these bodies. That is, after planets have been captured in the same resonance, tidal forces cause the planets to leave their commensurabilities until they are captured in a different resonance. The latter motivated us to examine the validity of this scenario, both during the formation of resonant chains and also as a post-formation phenomenon.

To determined the probability of forming resonant chains and capture in different resonances, we carried out more than 2700 simulations of multiple-planet migration, where fully formed planets were migrating while interacting with one another, and more than 60 simulations of planet formation in a protoplanetary disk subject to the perturbation of migrating planets. Simulations were carried out for different values of planets’ masses and migration rates, and the number of migrating planets.

Figure 1 shows the results. As shown here, from all our simulations, only 130 (~5%) resulted in captures into resonances suggesting that multi-planet resonances are not a common occurrence. The largest number of captures appears for 5:3 (a new finding) followed by 3:2 and 2:1 resonances. Results also showed that the probability of capture (and, therefore, the final commensurabilities) is highly depended on the characteristics of the systems, especially the planets’ mass-ratio and migration speed. Figure 2 shows a sample of our planet formation simulations in which planets form in a protoplanetary disk that is subject to the perturbation of three migrating giant planets. As shown here, after 1 Myr, super-Earth and larger planet are formed with some being mutually captured in resonances (i.e., forming a resonant chain).

Our simulations also demonstrated that capture in a resonance never occurs at the resonance’s exact commensurability and there is always some deviation (Figure 3). The extent of this deviation also depends on the mass-ratio and orbital characteristics of the planets and the mechanism through which migrating planets lose energy.

Collectively, our results confirm that, 1) migrating planets can be captured in different resonances and that the diversity of resonances observed in resonant chains is a natural consequence of the formation and resonance capture mechanism, and does not require a secondary, post-formation process, and 2) no post-capture mechanism is needed to explain the deviation from exact commensurabilities observed in Kepler (and RV) planet pairs.    











How to cite: Haghighipour, N.: Size and resonance diversity of multi-planet resonant chains is a natural outcome of their formation, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-303,, 2022.

Aurélie Astoul and Adrian Barker

In close exoplanetary systems, tidal interactions are known to shape the orbital architecture of the system, modify star and planet spins, and have an impact on the internal structure of the bodies through tidal heating. Most stars around which planets have been discovered are low-mass stars and thus feature a magnetised convective envelope, as is also expected in giant gaseous planets like Hot-Jupiter. Tidal flows, and more specifically inertial waves (restored by the Coriolis acceleration, and recently discovered in the Sun) tidally-excited, are the main direct manifestation of tidal interactions in the convective envelopes of these bodies. Furthermore, inertial waves are small-scale waves that are sensitive to nonlinearities, especially in close Hot-Jupiter systems with strong tidal forcing. The nonlinear self-interaction of inertial waves is known to trigger differential rotation in convective shells, as shown in numerical and experimental hydrodynamical studies. Since inertial waves are a key contribution to the tidal dissipation in close star-planet systems, it is essential to have the finest understanding of tidal inertial wave propagation and dissipation in such a complex nonlinear, magnetised, and differentially rotating environment.
In this context, we investigate how nonlinearities affect the tidal flow properties, thanks to new 3D hydrodynamic and magneto-hydrodynamic nonlinear simulations of tides, in an adiabatic and incompressible convective shell. First, we show to what extent the emergence of differential rotation is modifying the tidal dissipation rates, prior to linear predictions. In this newly generated zonal flows, nonlinear self-interactions of tidal inertial waves can also trigger different kind of instabilities and resonances between the waves and the background sheared flow, when the tidal forcing is strong enough or the viscosity low enough. These different processes disrupt the energetic exchanges between tidal waves and the background flow, and also further modifies the tidal dissipation rates. Secondly, we present the first non-linear numerical analysis of tidal flows in a magnetised convective shell. One main effect of the magnetic field in our model is to mitigate zonal flows triggered by the nonlinear interaction of inertial waves. The consequences for tidal flows are important, since the installation of zonal flows in nonlinear hydrodynamical simulations is the main cause of significant changes in tidal dissipation and angular momentum exchanges, compared to linear predictions for a uniformly rotating body. 

How to cite: Astoul, A. and Barker, A.: Nonlinear tidal interactions in the convective envelopes of low-mass stars and giant gaseous planets, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1198,, 2022.

Luisa Maria Serrano

It is commonly accepted that exoplanets with orbital periods shorter than one day, also known as ultra-short-period (USP) planets, formed further out within their natal protoplanetary disks before migrating to their current-day orbits via dynamical interactions. One of the most accepted theories suggests a violent scenario involving high-eccentricity migration followed by tidal circularization. Here we present the discovery of a four-planet system orbiting the bright (V=10.5) K6 dwarf star TOI-500. The innermost planet is a transiting, Earth-sized USP planet with an orbital period of nearly 13hours, a mass of 1.42±0.18Earth Masses, a radius of 1.166±0.061 Earth Radii and a mean density of 4.89±1.03gcm-3. Via Doppler spectroscopy, we discovered that the system hosts 3 outer planets on nearly circular orbits with periods of 6.6, 26.2 and 61.3 days and minimum masses of 5.03±0.41 Earth Masses, 33.12±0.88 Earth Masses and 15.05±1.12 Earth Masses respectively. The presence of both a USP planet and a low-mass object on a 6.6-day orbit indicates that the architecture of this system can be explained via a scenario in which the planets started on low-eccentricity orbits then moved inwards through a quasi-static secular migration. Our numerical simulations show that this migration channel can bring TOI-500 b to its current location in 2Gyr, starting from an initial orbit of 0.02au. TOI-500 is the first four-planet system known to host a USP Earth analogue whose current architecture can be explained via a non-violent migration scenario.

Published on Nature Astronomy (

How to cite: Serrano, L. M.: A low-eccentricity migration pathway for a 13-h-period Earth analogue in a four-planet system, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-703,, 2022.

Coffee break
Chairperson: Anne-Sophie Libert
Dynamical characterization
Vincent Bourrier and Adrien Deline and the CHEOPS and HARPS-N consortia

Much remains to be understood about the nature of exoplanets smaller than Neptune, most of which have been discovered in compact multi-planet systems. With its inner ultra-short period planet b aligned with the star and two larger outer planets d/c on polar orbits, the multi-planet system HD 3167 features a peculiar architecture and offers the possibility to investigate both dynamical and atmospheric evolution processes. To this purpose we combined multiple datasets of transit photometry and radial velocimetry to revise the properties of the system and inform models of its planets. This effort was spearheaded by CHEOPS observations of HD3167b, which appear inconsistent with a purely rocky composition despite its extreme irradiation. Overall the precision on the planetary orbital periods are improved by an order of magnitude, and the uncertainties on the densities of the transiting planets b and c are decreased by a factor 3. Internal structure and atmospheric simulations draw a contrasting
picture between HD3167d, likely a rocky super-Earth that lost its atmosphere through photo-evaporation, and HD3167c, a mini-Neptune that kept a substantial primordial gaseous envelope. We detect a fourth, more massive planet on a larger orbit, likely coplanar with HD3167d/c. Dynamical simulations indeed show that the outer planetary system d/c/e was tilted as a whole early in the system history, when HD3167b was still dominated by the star influence and maintained its aligned orbit. RV data and direct imaging rule out that the companion that could be responsible for the present-day architecture is still bound to the HD3167 system. Similar global studies of multi-planet systems will tell how many share the peculiar properties of the HD3167 system, which remains a target of choice for follow-up observations and simulations.

How to cite: Bourrier, V. and Deline, A. and the CHEOPS and HARPS-N consortia: A CHEOPS-enhanced view of the HD3167 system, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-954,, 2022.

Maximilian N. Günther

The nearby TOI-270 system provides an unparalleled opportunity to observationally probe hypotheses for exoplanet formation and evolution. The system hosts one super-Earth and two sub-Neptunes near mean-motion resonances and transiting a bright (K-mag 8.25) M3V dwarf. Strangely, M-dwarf systems harbouring only super-Earths or only sub-Neptunes are ubiquitous. However, for still unknown reasons, systems with multiple planets spanning the radius valley are rare - and we know merely a handful of systems bright enough for precise mass measurements and atmospheric studies. To this end, TOI-270's planets are exceptionally favourable for detailed transit timing variation (TTV) and transmission spectroscopy observations. First, with the planets orbiting near low-order resonances (5:3 and 2:1), our extensive observing campaign with eight different observatories since 2018 yields clear TTV signals for planets c and d, with amplitudes of around 10 min and a super-period of circa 3 yr. Using dynamical models, we can thus significantly constrain their radii, mass ratios, and eccentricities. This adds to complementary radial velocity (RV) mass measurements from HARPS and ESPRESSO. Second, via HST and JWST transmission spectroscopy we can characterise and compare the atmospheres of two sub-Neptunes formed from the same protoplanetary nebula and test hypotheses like photoevaporation, core-powered mass-loss, and gas-poor formation. As one of the best-constrained small planet systems, TOI-270 can thus serve as a unique observational testbed for formation and evolution theories. 

How to cite: Günther, M. N.: TOI-270 as a unique testbed for exoplanet formation & evolution, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1183,, 2022.

Carolina Charalambous, Jean Teyssandier, and Anne-Sophie Libert

Planetary formation theories predict that planets can be captured in mean-motion resonances (MMRs) during the migration process in the protoplanetary disc. However, among the discovered extrasolar planets, there is an enormous variety of orbital architectures and generally the planet pairs are not precisely found at the nominal resonance, but instead present a resonant offset slightly exterior to it.

In this work we focus on Kepler-80 which falls into the category known as STIPs: Systems with Tightly packed Inner Planets. The planets of these systems are believed to form farther from the star and then migrate inward while the disc is present. Once the disc disperses, tidal interactions with the central star become important, usually slowly pushing the planets outwards.

Kepler-80 is a 6-planet STIP which exhibits a particular dynamical configuration. The planets are in 2 and 3-planet MMRs and the observed resonant offset grows with the distance to the star. We aim to understand whether the tides can generate this particular configuration of the offsets. To do so, we propose a realistic scenario for the formation of Kepler-80 and analyze how the tidal effects can transport from the inner planets to the outer ones through the resonances of the system.

How to cite: Charalambous, C., Teyssandier, J., and Libert, A.-S.: Offsets in Laplace resonances: The case of Kepler-80, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-976,, 2022.

Mariah MacDonald

The study of orbital resonances allows for the constraint of planetary properties of compact systems. Mean motion resonance occurs when two or more planets repeatedly exchange angular momentum and energy as they orbit their host star, since the planets will always conjunct at the same point in their orbits. We can predict a system's resonances by observing the orbital periods of the planets, as planets in or near mean motion resonance have period ratios that reduce to a ratio of small numbers. However, a period ratio near commensurability does not guarantee a resonance; we must study the system's dynamics and resonance angles to confirm resonance. Because resonances require in-depth study to confirm, and because two-body resonances require a measurement of the eccentricity vector which is quite challenging, very few resonant pairs or chains have been confirmed. We thus remain in the era of small number statistics, not yet able to perform large population synthesis or informatics studies. To address this problem, we build a python package to find, confirm, and analyze mean motion resonances, primarily through N-body simulations. We verify our package by recovering the known resonances of Kepler-80 and Kepler-223. We then demonstrate the package’s functionality and potential by confirming new resonances, characterizing the mass-eccentricity degeneracy of Kepler-80g, and exploring the likelihood of an exterior giant planet in Kepler-80 and Kepler-223. We also study the formation history of K2-138 and constrain the planets’ masses and orbital parameters.

How to cite: MacDonald, M.: New Python package to find, confirm, and characterize mean motion resonances, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-169,, 2022.

Anastasiia Nahurna, Mykhailo Solomakha, Mariia Lobodenko, and Olexandr Baransky

We report the results of the investigation of five planetary systems TrES-3b, Kepler-17b, WASP-3b, Qatar-1b, and Qatar-2b. For the exoplanets TrES-3b, Kepler-17b, WASP-3b, and Qatar-1b, the obtained results of the center-transit time, depth and length of transit agree with the ephemeris data, while for two observations of the Qatar-2 system for the planet Qatar-2b there is a clear decreasing trend of the value of the O-C parameter.

Observations were carried out from 2 April 2021 to 14 February 2022 by using a 70-cm reflecting telescope AZT-8 on the Astronomical Observatory of Taras Shevchenko National University of Kyiv / Kyiv comet station (Kyiv, Ukraine). Photometric processing of the observation results was performed by using the Muniwin program. The obtained exoplanet transit brightness curves were published in ETD. The accuracy and quality of our observations on the ETD database scale ranged from 1 to 3.

Additionally, applying the method of time transit variation (TTV) to our and Exoplanet Transit Database (ETD) data, we found a possible gravitational effect on the orbit of the exoplanet Qatar-2b of another massive body. This suggests that the assumption of the existence of the planet Qatar-2c conjectured in Bryan et al. (2011) is true.

How to cite: Nahurna, A., Solomakha, M., Lobodenko, M., and Baransky, O.: Investigation of planetary systems of WASP, TrES, Qatar and Kepler projects by using transit photometry with O-C parameter tracking and TTV method application on Kyiv Comet Station, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-200,, 2022.

Manu Stalport, Jean-Baptiste Delisle, Stéphane Udry, Elisabeth Matthews, Vincent Bourrier, and Adrien Leleu

The formation and evolution of planetary systems has been, and remains, one of the big questions of Science. With more than 800 multi-planet systems discovered so far, as many outcomes of these formation and evolution processes are in reach of characterization. These represent precious pieces of the big puzzle. In order to obtain the most from these constraints, a precise knowledge of each system's architecture is crucial: it is key to identify the leading processes in shaping those systems, and hence relate their present state to their formation stage.


In this presentation, I will introduce a technique aiming at refining the planetary orbital parameters and masses (Stalport et al. 2022). This technique uses orbital stability arguments on top of a bayesian approach for the parameters' estimation. The estimation of orbital stability is based on short N-body numerical integrations together with the Numerical Analysis of Fundamental Frequencies (NAFF) fast chaos indicator (Laskar 1990), for which we propose a calibration strategy to scale chaos. The stability information is finally included a posteriori in the planetary parameters' posterior through importance sampling, after which new distributions of stable-only solutions are built.

This stability-driven refinement technique can be applied on any type of multi-planet systems, and notably in the context of planets in binaries. Besides the advantage of reducing the uncertainties on the dynamical parameters (orbital elements and planetary masses), such an approach can also provide additional insights into the dynamical states of the studied systems. I will present the revision of a few multi-planet systems in light of our approach, and particularly, I will describe a comprehensive dynamical analysis of the Kepler-444 planetary system (Stalport et al. submitted to A&A).


Approaches such as the one presented here are timely. They represent a way of getting the best constraints on planetary systems' architectures within limited observational datasets. I will stress for the importance of carrying a systematic revision of multi-planet systems under the loop of orbital stability. 

How to cite: Stalport, M., Delisle, J.-B., Udry, S., Matthews, E., Bourrier, V., and Leleu, A.: An orbital stability-driven approach for the refinement of multi-planet systems’ architectures, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-720,, 2022.

Display time: Mon, 19 Sep 08:30–Wed, 21 Sep 11:00

Posters: Mon, 19 Sep, 18:45–20:15 | Poster area Level 2

Chairpersons: Anne-Sophie Libert, Antoine Petit
Jeanne Davoult, Lokesh Mishra, and Yann Alibert

Context: The detection of Earth-like planets is both one of the major goals of planetology and at the same time one of the most complicated. Earth-like planets are difficult to detect and imply a lot of observation time with the current detection methods. Currently only 0.06% of the confirmed exoplanets are similar to Earth by their masses and semi-major axis.

Aims:  Here, a way to identify systems, which are likely to harbor an Earth-like planet, is considered.  This can facilitate the selection of targets and reduce the time necessary for observations.

Methods: Mishra et. al 2022 (to be submitted) have developed a method for classifying planetary systems according to their architecture. Applied on generation III Bern model synthetic population, a class has been identified in which a majority of systems harbors an Earth-like planet. Using the same classification scheme now taking into account the observational bias, we investigate whether the observed class of a system (the one obtained only from observable planets) could help to find systems more likely to have an Earth-like planet.

Results: The classes in themselves with only the detectable planets are not sufficient to identify systems with an Earth-like planet, but the characteristics of the remaining planets and the prognostic of the intrinsic architecture is a solid base for such a conjecture

References: [1] Mishra L. et al. (2022) To be submitted. [2] Davoult J. In prep..

How to cite: Davoult, J., Mishra, L., and Alibert, Y.: On planetary systems classification and Earth-like planet, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-6,, 2022.

Andrin Kessler, Yann Alibert, Christoph Mordasini, Alexandre Emsenhuber, and Remo Burn


High-precision measurements of isotopes in meteorites suggest that the early population of small bodies in the Solar System has been separated into two reservoirs by the forming Jupiter, acting as a radial barrier for these 'planetesimals' [1]. In a proposed Jupiter formation scenario [2], the solid core must grow within 1 Myr to around 20 Earth masses, then stagnate its growth for 2-3 Myr and thus separating the planetesimal reservoirs, and finally grow to the final Jupiter mass stirring and mixing the inner and outer planetesimals. The fast and early core growth is efficiently facilitated by the accretion of small 'pebble-like' objects. In order to delay the otherwise inevitable rapid runaway gas accretion for an extended period of time after the pebble accretion stops, Jupiter is proposed to be heated by slower planetesimal accretion before finally becoming massive enough to accrete a large amount of gas, reaching its present day mass.

Motivated by this proposed formation scenario of Jupiter, we investigate the consequences of a combined pebble and planetesimal accretion model for the formation of giant planets and planet formation in general [3]. We modify the Bern model of planetary population synthesis [4] with a simple model of pebble formation and accretion [5]. In a single-planet population synthesis approach, we run the model on a thousand different initial protoplanetary disks in order to probe the effects of the two solid accretion mechanisms on a population level. To uncover the interplay of the two models, we vary the amount of pebbles with respect to planetesimals.

As shown in figure 1, it proves to be difficult to form giant planets from the accretion of pebbles and planetesimals whereas both mechanisms individually are able to form giants in suitable disks. We identify the remaining accretion of planetesimals after the stop of pebble accretion to be crucial for the formation pathway of a growing planet. The envelope heating due to the accretion of solids is shown to play a critical role for the accretion of gas. A combination of enhanced inward orbital migration and delayed runaway gas accretion strongly suppresses the formation of giants in disks containing both pebbles and planetesimals.


Figure 1: Planet mass over semi-major axis snapshot after 2 Gyr of evolution for populations of one thousand disks, containing one planet. The four, otherwise identical, populations start with either only planetesimals (left), 30% pebbles (middle left), 70% pebbles (middle right), or only pebbles (right).


[1] Kruijer T. S., Burkhardt C., Budde G., Kleine T., 2017, Proc. Natl. Acad. Sci., 114, 6712

[2] Alibert Y., Venturini J., Helled R., et al., 2018, Nature Astronomy, 2, 873

[3] Kessler A., et al., in prep.

[4] Emsenhuber A., Mordasini C., Burn R., et al., 2021, A&A, 656, A 69 

[5] Bitsch B., Lambrechts M., Johansen A., 2015b, A&A, 582, A 112

How to cite: Kessler, A., Alibert, Y., Mordasini, C., Emsenhuber, A., and Burn, R.: Giant Formation with Pebbles and Planetesimals, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-114,, 2022.

Nicolas Kaufmann and Yann Alibert

The size distribution of solids in the protoplanetary disk is still ill constrained [1] but is a vital parameter that influences planetary growth [2]. The typical size and spatial distribution of solids evolves throughout the planet formation process via collisions and radial drift. As the planets grow, they excite the mutual random velocities among planetesimals making their mutual collisions destructive which leads to fragmentation, reducing their typical size. This effect of self-interacting planetesimals has been found to inhibit or favor the formation of planets due to competing effects of easier accretion of smaller fragments and depletion by gas-drag induced drift [3-4]. However, previous studies have either focused on single planets and systems or have neglected concurrent effects like migration.

Therefore, we run planet formation simulations with the generation III Bern model [5] with a Eulerian 1D solid disks. The model tracks the growth and evolution of several planetary embryos from oligarchic growth to the final planetary system. We added to it a fragmentation toy model [6] to see the impact fragmentation has on planet formation. To see its influence on the diverse types of exoplanets we make use of a population synthesis approach to investigate larger parts of the parameter space [7]. This allows us to have a more complete picture of what influence the collisional evolution of planetesimals has on planet formation and to study the effects that arise from its interplay with the formation of multiple planets in the same system.

In figure 1, we show two exemple synthetic planet populations of 1000 systems with (right) and without (left) the added fragmentation model. We find multiple interesting features in our synthetic populations that arise from the fragmentation of planetesimals. The fragmentation lends more importance to specific locations in the disk where growth is enhanced like the ice line and the inner disk. In addition, it enhances the formation of giants.

In conclusion, there are significant differences in synthetic populations when including or neglecting fragmentation. This suggests that the addition of fragmentation to global planet formation models is important as a self-consistent solid disk description is vital to understand planet formation.

In figure 1. Comparison of a synthetic exoplanet population without (left) the added fragmentation model and one with (right).  The semi major axis (in AU – log scale) is plotted on the x-axis and the planetary mass (in Earth masses – log scale) on the y-axis. Both populations are shown at an age of 5 Gyr. The Red points refer to planets with more envelope than core mass, the blue ones are icy planets (ice mass fraction larger than 1%) and the green points are rocky planets (ice mass fraction smaller than 1%).




[1] Helled, R. & Morbidelli, A. 2021, in ExoFrontiers (IOP Publishing)

[2] Fortier, A., Alibert, Y., Carron, F., Benz, W., & Dittkrist, K.-M. 2012, A&A, 549, A44

[3] Guilera, O. M., de Elía, G. C., Brunini, A., & Santamaría, P. J. 2014, A&A, 565, A96

[4] Chambers, J. 2008, Icarus, 198, 256

[5] Emsenhuber, A., Mordasini, C., Burn, R., et al. 2021, A&A, 656, A69

[6] Ormel, C. W. & Kobayashi, H. 2012, The Astrophysical Journal, 747, 115

[7] Emsenhuber, A., Mordasini, C., Burn, R., et al. 2021b, A&A, 656, A70

How to cite: Kaufmann, N. and Alibert, Y.: A population level study on the influence of planetesimal fragmentation on planet formation, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-135,, 2022.

Laurent Schönau, Tunahan Demirci, Jens Teiser, Tetyana Bila, Kolja Joeris, Florence Chioma Onyeagusi, Niclas Schneider, Miriam Fritscher, Felix Jungmann, Maximilian Kruss, Lars Schmidt, and Gerhard Wurm

In the formation of a planetary system, the objects involved pass through a wide range of sizes starting with micrometre-sized particles and ending up as full-grown planets. An intermediate step in this evolution is represented by kilometre-sized planetesimals, which might consist of very loosely bound millimetre dust granules [1]. Their orbital velocity differs from that of the surrounding gas in the protoplanetary disk resulting in a headwind with relative velocities of the order of 50 m/s [2]. Since self gravity of such a planetesimal is very small, there is a possibility that it loses mass due to wind erosion. This raises the question at which wind speeds and ambient pressures the planetesimal is stable and at which it is not.

To recreate wind erosion on planetesimals in protoplanetary disks as realistically as possible, low pressures and a microgravity environment are needed. The latter can be achieved by placing an experiment in an aircraft that performs parabolic flights (A310 ZERO-G by Novespace). In a cylindrical vacuum chamber a second smaller cylinder is located in its center and can rotate at high frequencies up to 200 Hz to create a shear flow. With this setup, a laminar wind profile can be generated over a simulated planetesimal surface placed within at ambient pressures down to 10-2 mbar.

We used this setup with millimetre dust aggregates consisting of SiO2. The aggregates were produced in an analogous way as dust aggregates at the bouncing barrier in protoplanetary disks might form, i.e. by collisions of micrometre-sized particles, sticking and growing up to the bouncing size. This experimental setup has already been used in previous parabolic flight campaigns with glass spheres as sample [3]. This time, a more realistic approach was applied with these SiO2 aggregates.

Wind erosion was observed at an ambient pressure that was an order of magnitude lower than before. Furthermore, by accurately measuring the residual gravity during the microgravity phases, it was possible to determine an angle of repose under the given conditions. Here we report the latest results of the parabolic flight campaigns.

Applied to planet formation, our results support and expand earlier findings that wind erosion might generate forbidden zones for pebble pile planetesimals, i.e. closer to the star [3,4] and wind erosion might filter out excentric orbits [5].



[1] Wahlberg Jansson K., Johansen A., Bukhari Syed M., Blum J., 2017, ApJ, 835, 109

[2] Weidenschilling S. J., 1977, MNRAS, 180, 57

[3] Demirci T., Schneider N., Steinpilz T., Bogdan T., Teiser J., Wurm G., 2020, MNRAS, 493, 5456-5463

[4] Rozner M., Grishin E., Perets H. B., 2020, MNRAS, 496. 4827-4835

[5] Cedenblad L., Schaffer N., Johansen A., Mehlig B., Mitra D., 2021, ApJ, 921, 123



This project is funded by DLR space administration with funds provided by the BMWK under grant 50 WM 2140. T. B. is funded by DLR space administration with funds from the BMWK under grant 50 WM 2049. K. J. is funded by DLR space administration with funds from the BMWK under grant 50 WM 1943. F. C. O., F. J. and M. K. are funded by DLR space administration with funds from the BMWK under grant 50 WM 2142. N. S. is funded by the DFG under grant WU 321/16-1. M. F. is funded by the DFG under grant TE 890/7-1. We also thank M. Aderholz who helped bringing the idea of this experiment to real life.

How to cite: Schönau, L., Demirci, T., Teiser, J., Bila, T., Joeris, K., Onyeagusi, F. C., Schneider, N., Fritscher, M., Jungmann, F., Kruss, M., Schmidt, L., and Wurm, G.: Shaping planetary systems early on: Experimental view on wind induced erosion of planetesimals, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-232,, 2022.

Maximilian Zimmermann and Elke Pilat-Lohinger

1. Introduction

About 50 % [1] of solar-like stars are part of binary star systems. From the nearly 5000 exoplanet candidates only about 2171 are part of a binary or multiple star systems. Inclined planets have been found in circumbinary motion, nevertheless, there are also planets in circumstellar motion which indicate inclinations. Like in the binary star systems HIP 94235 b [2] (recent) and 55 Cnc e [3].

In this study, we want to investigate the late stage of terrestrial planet formation in S-type motion in close binary star systems with a focus on the evolution of the planetesimal disk.


2. Methods and Setup

To solve the equations of motion the Bulirsch-Stoer (BS) method is applied. As the n-body problem scales with O(N2) the BS method has been heavily parallelized on GPUs. As a first approximation for the collisions the so-called “perfect merging“ has been applied. In our numerical study, the interaction of some thousands disk objects are studied for 1 Myrs.

For an equal mass G-type binary star the following star parameters have been varied: ab , eb , and ib. The circumprimary disk consists of some tens of planetary embryos and 2000 planetesimals and extends between 1 and 4 au. The disk is initially dynamically cold and is within the area of stable motion [4]. The different configurations have been simulated for a time of 1 Myr each. For some selected configurations we increased the simulation time for 10 Myr.

3. Results

The wider binary (100 , 150 au) configurations show a bend in the inclination (see figure 1). The location of the bend is closer to the primary for the 100 au (∼ 2.0 au) case than in the 150 au (∼ 2.5 au) case. Additionally, in the 100 au binary star, the innermost embryos reach inclinations up to ∼ 50° compared to ∼ 30° in the 150 au binary system.