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


The hidden newly born planets 

The spatially resolved characterization of planet-forming disks carried out over the last decade suggests that massive planets form very soon after a star is born. Nonetheless, newly born planets remain very elusive and up to date, we only have one confirmed young exoplanet system embedded in the natal disk.

On the one hand, the census of planet-forming disks depicted by ALMA revealed a number of substructures that are ascribed to the disk interaction with forming planets. The exquisite data quality achieved by some datasets even enabled the prediction of the mass and location of the putative planets. On the other hand, the most promising technique aimed at detecting such planets, that is the direct imaging in the near-infrared, has so far yielded limited results.

In this session, we bring together experts from different disciplines of the planet formation in order to review what are the reasons to believe (or not) that planets embedded in disks are common but elusive as well as what is the best strategy to reveal their existence in the near future.

Convener: Antonio Garufi | Co-conveners: Paola Pinilla, Feng Long, Stefano Facchini, Farzana Meru
| Tue, 20 Sep, 10:00–11:30 (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: Tue, 20 Sep | Room Andalucia 3

Chairpersons: Antonio Garufi, Paola Pinilla, Feng Long
Marion Villenave

To form giant planets in protoplanetary disk lifetime, small micron sized particles must grow rapidly to larger grains. A full understanding of that process requires a detailed characterization of the radial and vertical structure of the gas-rich disks associated with young pre-main sequence stars. Disks observed edge-on are of particular interest as they provide a unique point of view to unambiguously disentangle their vertical and radial dimensions. Here we present ALMA extremely high angular resolution imaging (up to a few AU scales) of one edge-on disk in the nearby Ophiuchus star-forming region. The modeling of the millimeter continuum image and a previously published scattered light image with radiative transfer enables a robust comparison of the spatial distribution of millimeter-sized grains and micron-sized dust grains in this disk. We find that the large dust grains are constrained to a remarkably flat subdisk as a consequence of dust settling. We place stringent constraints on the thickness of this subdisk in this system, on vertical settling efficiency, and on the potential for wide-orbit planet formation in this disk. 

How to cite: Villenave, M.: Extremely flat protoplanetary disks: a favorable environment for planetary growth, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-88,, 2022.

Joanna Drazkowska

With the increasing observational capabilities of the young stars and their surrounding disks bringing new constraints on the planet formation process, planet formation theory is undergoing major changes. One of the significant paradigm shifts is the belief that the first planetary cores start forming early, possibly during the circumstellar disk buildup process.

I will review the current understanding of planet formation, including dust growth to pebbles, formation of the first gravitationally bound planetesimals, and the growth of planetary cores by accretion of planetesimals and pebbles. I will highlight the possible pathways to early planet formation, stressing that the planet formation process may not be spatially uniform in the disk and that there are preferential locations for the formation of the early planetesimals and planets, such as the water snow line or dust traps. 

How to cite: Drazkowska, J.: Theoretical perspective on early planet formation, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-259,, 2022.

Jane Huang

High angular resolution observations of protoplanetary disks at millimeter and near-infrared wavelengths have revealed an impressive variety of substructures, including gaps and rings, spiral arms, warps, and asymmetries. Models have suggested that many of these structures can be produced through planet-disk interactions. These substructures can therefore open a window into the properties of protoplanets that are below the limits of what current direct imaging technology can probe. I will review recent observations of disk substructures and how they have been used to infer the masses and orbital properties of embedded protoplanets. I will also comment on alternative interpretations of these disk substructures and what future observations will help to break degeneracies. 

How to cite: Huang, J.: Inferring characteristics of the young planet population from high resolution protoplanetary disk imaging, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-308,, 2022.

Davide Fedele

Among all the detection of exoplanets, the esistence of giant planets on wide orbits (r > 100 au) is of major importance to test the planet formation mechanism. At such distance from the star, grain growth is inhibited primarily by the low dust density. Gravitational instability might be at work in (some) disks. And yet, according to the measurements of the total gas mass, disks do not appear to be gravitationally unstables. The occurence of such 'cold Jupiters' remains a puzzle. Interestingly, the recent ALMA high angular resolution campaigns do show the presence of dust gaps and rings in protoplanetary disks on wide orbits, on spatial scales similar to those of cold Jupiters. In this regard, HD 100546 is a remarkable system.  

The protoplanetary system HD 100546: HD 100546 is a 2.5 solar mass star surrounded by a large disk extending out to nearly 500 au. The disk show spiral arms at different spatial scales, an inner dust cavity of nearly 28 au radius, a wide dust gap between nearly 50 and 150 au and a faint and eccentric outer ring centered at 200 au. Figure 1 shows the distribution of the millimeter continuum as seen by ALMA. The peculiar disk structures can be explained with the presence of two giant protoplanets (orbiting at at nearly 15 au and 100 au) interacting with the surrounding gas and dust. Notably, HD 100546 is one of the only disk in which cold water emission has been detected. I will present some recent ALMA results along with hydrodynamical simulations and a new analysis of the water distribution in the disk.

How to cite: Fedele, D.: The embedded giant protoplanets in HD 100546, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-461,, 2022.

Jacob B. Simon and Daniel Carrera

A crucial step in the planet formation process is the formation of smaller bodies known as planetesimals.  However, how these small bodies formed is one of the largest outstanding issues in planetary science and astronomy. One promising route is a process known as the streaming instability, the end product of which is enhanced concentration of dust grains in the gaseous planet-forming disk.  However, even this instability requires an initial enhancement in grain concentration to get started. This initial enhancement can occur in axisymmetric regions of relatively high gas pressure known as pressure bumps; inwardly drifting dust grains slow down as they enter the bump, leading to a localized enhancement. 

Here, I present a series of very high-resolution simulations of grain concentration + streaming instability in axisymmetric pressure bumps at stellar distances equivalent to the Cold Classical Kuiper Belt.  We find that planetesimal formation via this process is extremely robust for cm-sized grains, but completely fails for mm-sized grains unless the pressure bump is sufficiently large in amplitude to completely trap the inwardly drifting grains. However, such large pressure bumps are likely to be themselves unstable and break down into vortices. Furthermore, models suggest that grains cannot grow beyond mm sizes at these distances.

Our main conclusion is that either planet-forming disks form grains larger than ~1 mm , or planetesimals do not form by the streaming instability in pressure bumps.  This result has a number of important implications for early planet formation, including alternative routes towards planetesimal formation.  I will conclude with a brief discussion of these implications.

How to cite: Simon, J. B. and Carrera, D.: Planetesimal Formation (or Lack Thereof) in Pressure Bumps and Implications for Early Planet Formation, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-519,, 2022.

Valentin Christiaens, Benoit Pairet, Sandrine Juillard, Josh Calcino, and Clément Baruteau

With its large sub-mm continuum cavity, asymmetric clumps and spiral arms, the disc of MWC 758 is an ideal test laboratory to search for embedded planets at an early stage of formation and study their dynamical interplay with the disc. As such, two protoplanet candidates have been proposed in this disc by independent teams based on thermal IR high-contrast imaging data, which both require confirmation. In this contribution, I will compare three novel algorithms that we designed to alleviate current shortcomings stemming from the application of state-of-the-art Angular Differential Imaging (ADI)-based algorithms - namely geometric biases induced to azimuthally extended signals from the aggressive modeling and subtraction of the stellar halo. The first algorithm relies on an iterative approach, while the other two rely on an inverse-problem approach, with and without regularisation terms, respectively, to recover the unbiased circumstellar intensity distribution. I will show the images obtained from the application of these algorithms to the case of MWC 758, for which we considered the SPHERE (H23) and NIRC2 (L’) datasets obtained in the best observing conditions for this study. I will then compare these images to predictions from hydro-dynamical simulations testing the hypotheses of a single (internal) eccentric companion, and two giant (internal+external) planets on circular orbits, respectively, and will discuss the likelihood of each scenario based on the similarity to our new images.

How to cite: Christiaens, V., Pairet, B., Juillard, S., Calcino, J., and Baruteau, C.: A comparison of novel algorithms for unbiased recovery of extended disk signals with ADI - Application to the case of MWC 758 and its protoplanet candidates., Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1137,, 2022.

Sahl Rowther, Rebecca Nealon, and Farzana Meru
We carry out three dimensional smoothed particle hydrodynamics simulations to study the impact of planet-disc interactions on a gravitationally unstable protoplanetary disc. We find that the impact of a planet on the disc's evolution can be described by three scenarios. If the planet is sufficiently massive, the spiral wakes generated by the planet drive the evolution of the disc and gravitational instabilities are completely suppressed. If the planet's mass is too small, then gravitational instabilities are unaffected. If the planet's mass lies between these extremes, gravitational instabilities are weakened. We present mock Atacama Large Millimeter/submillimeter Array (ALMA) continuum observations showing that the observability of large-scale spiral structures is diminished or completely suppressed when the planet is massive enough to influence the disc's evolution. Our results show that massive discs that would be expected to be gravitationally unstable can appear axisymmetric in the presence of a planet. Thus, the absence of observed large-scale spiral structures alone is not enough to place upper limits on the disc's mass.

How to cite: Rowther, S., Nealon, R., and Meru, F.: Hiding Signatures of Gravitational Instability in Protoplantery Discs with Planets, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-775,, 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

Oliver Schib, Christoph Mordasini, and Ravit Helled

Disk instability remains the leading formation pathway for some of observed giant planets. In particular, this model can more naturally explain giant planets at large separation, giant planets around M stars, and very young giant planets. However, there are still many open questions regarding this formation mechanism, and the expected population of planets.
We are working on a new disc instability population synthesis (DIPSY) that aims to address these questions and make predictions about the expected population of planets that can be tested observationally.
We find that fragmentation (the formation of bound clumps in the disc, a necessary condition for planet formation in the disc instability model) depends sensitively on the precise physics during the disc formation (infall). We show that infall models that form discs compatible in size with observed young discs are likely to fragment, though this may happen only in a minority of systems. Furthermore, we demonstrate how the intrinsics of orbital migration, mass accretion and clump interaction influence the fate of the formed clumps.
The figure shows the fraction of systems that fragment as a function of the final stellar mass for different parameters studied [1].
The results of the population synthesis, combined with current and future observations, will deepen our understanding of planet formation irrespective of the formation model.

Fig. 1: Fraction of fragmenting discs as a function of the final stellar mass for different parameters. When an infall model motivated by non-ideal MHD simulations is applied, no fragmentation occurrs. In contrast, infall informed by radiation hydrodynamic simulations leads to a substantial fraction of discs fragmenting, especially at higher masses.


[1] Schib, O., Mordasini, C., Wenger, N., Marleau, G. D., & Helled, R. 2021, Astronomy and Astrophysics, 645, A43

How to cite: Schib, O., Mordasini, C., and Helled, R.: DIPSY: A New Disc Instability Population Synthesis, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-50,, 2022.

Camille Bergez-Casalou, Bertram Bitsch, Nicolas Kurtovic, and Paola Pinilla

New ALMA observations of protoplanetary disks allow us to probe planet formation in other planetary systems, giving us new constraints on planet formation processes. Meanwhile, studies of our own Solar System rely on constraints derived in a completely different way. However, it is still unclear what features the Solar System protoplanetary disk could have produced during its gas phase. By running 2D isothermal hydro-simulations used as inputs for a dust evolution model, we derive synthetic images at millimeter wavelengths using the radiative transfer code RADMC3D. We find that the embedded multiple giant planets strongly perturb the radial gas velocities of the disk. These velocity perturbations create traffic jams in the dust, producing over-densities different from the ones created by pressure traps and located away from the planets’ positions in the disk. By deriving the images at λ = 1.3 mm from these dust distributions, we show that very high resolution observations are needed to distinguish the most important features expected in the inner part (<15 AU) of the disk. The traffic jams, observable with a high resolution, further blur the link between the number of gaps and rings in disks and the number of embedded planets. We additionally show that a system capable of producing eccentric planets by scattering events that match the eccentricity distributions in observed exoplanets does not automatically produce bright outer rings at large radii in the disk. This means that high resolution observations of disks of various sizes are needed to distinguish between different giant planet formation scenarios during the disk phase, where the giants form either in the outer regions of the disks or in the inner regions. In the second scenario, the disks do not present planet-related features at large radii. Finally, we find that, even when the dust temperature is determined self-consistently, the dust masses derived observationally might be off by up to a factor of ten compared to the dust contained in our simulations due to the creation of optically thick regions. Our study clearly shows that in addition to the constraints from exoplanets and the Solar System, ALMA has the power to constrain different stages of planet formation already during the first few million years, which corresponds to the gas disk phase.

How to cite: Bergez-Casalou, C., Bitsch, B., Kurtovic, N., and Pinilla, P.: Constraining giant planet formation with synthetic ALMA images of the Solar System's natal protoplanetary disk, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-85,, 2022.

Matías Gárate, Paola Pinilla, Til Birnstiel, Barbara Ercolano, Sebastian M. Stammler, Giovanni Picogna, Timmy N. Delage, Jochen Stadler, Raphael Franz, Sean Andrews, and Anna Miotello

Transition disks are one of the enigmas of the planet formation process: These objects typically feature wide gaps in the dust component, along with deficit of NIR emission corresponding to a lack of small grains in the inner regions, but simultaneously require a gas rich inner disk capable of sustaining high accretion rates, and a high content of pebble sized grains to explain the emission detected in the millimeter continuum.
Massive planets of several Jupiter masses have been long proposed as an explanation for these objects. However, despite the efforts to find these giants, only one or two disks have confirmed detections of a planetary companion. We propose a new hybrid model that easily explain the properties of transition disks, by combining the contributions made by different research groups over the last decade in photoevaporation, dead zones, and dust trapping. In our model photoevaporation takes care of opening a cavity in the gas and dust component, while dead zones in the inner regions lead to long lived-inner disk, capable of sustaining the observed accretion rates during the photoevaporative dispersal process. Finally, dust trapped in moderate substructures (such as the ones caused by small Saturn mass planets) can explain the emissions found in the millimeter continuum, without imposing strong constrains on the planet location.
With our model we show that instead of invoking massive fine-tuned planets to explain all the transition disk properties, the different processes that occur in protoplanetary disks complement each other and naturally reproduce the transition disk observations. Then, perhaps the reason of why we don't find more hidden massive planets is, simply, because they are not there.

How to cite: Gárate, M., Pinilla, P., Birnstiel, T., Ercolano, B., Stammler, S. M., Picogna, G., Delage, T. N., Stadler, J., Franz, R., Andrews, S., and Miotello, A.: Explaining transition disks without massive planets, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-271,, 2022.

Emmanuel Di Folco, Anthony Boccaletti, Anne Dutrey, Ya-Wen Tang, Stephane Guilloteau, and Eric Pantin

AB Aur is a bright and young Herbig Ae star surrounded by a broad transitional disk, with a long record of detailed observations at various wavelengths. Multiple direct and indirect evidences for the presence of embedded proto-planets have been reported in the recent years in this system. A prominent double spiral pattern was first detected with ALMA in the molecular line emission of CO gas, with a large pitch angle in the most inner region, suggesting the presence of at least one sub-stellar body within the cavity of the dusty disk (R<120au). We obtained two epochs of observations of AB Aur with VLT/SPHERE (Dec. 2019 - Jan. 2022). The first polarimetric image showed a wealth of structures at several scales. Two spirals clearly overlap those detected with ALMA, although with a higher angular resolution. One of these spirals features a twist located at 0.18’’ from the star, reminiscent of structures predicted by the theory of density waves produced by a gravitational perturber onto the gas distribution. The analysis of the multi-epoch data shows changes consistent with Keplerian rotation with a protoplanet located at about 30au from the star. In addition, localized emissions could be attributed to additional planet candidates (which are otherwise expected in order to carve the large disk cavity), including the recent claim of a super-Jupiter near 90au from high-contrast near-IR imaging with Subaru-SCexAO. All these pieces of evidence make AB Aur one of the most promising young sources to investigate planet-disk interactions, and to unveil the close environment of accreting planets. I will report on the global (and detailed) analysis of the new observational results for this nascent planetary system, both in the context of the multi-epoch, and multi-wavelength SPHERE+ALMA images, and with the contribution of multi-fluid hydrodynamical simulations. 

How to cite: Di Folco, E., Boccaletti, A., Dutrey, A., Tang, Y.-W., Guilloteau, S., and Pantin, E.: How many forming planets in the transitional disk around AB Aurigae ?, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-313,, 2022.

The properties of disc-instability protoplanets embedded in their parent discs
Dimitris Stamatellos and Adam Fenton
Sandrine Juillard, Valentin Christiaens, Olivier Absil, and Myriam Benisty

Observing dynamical interactions between planets and disks is key to understanding their formation. Two protoplanets have recently been observed within PDS 70's transition disk, along with an extended signal towards the north-west of the star. In this contribution, I will present a temporal analysis of the PDS 70 disk morphology with the aim of assessing whether it could trace a spiral arm caused by the dynamical interaction between the planet PDS 70 c and the disk - or rather be the footprint of a vortex, which can mimic a spiral-arm in an inclined disk. I will show the PDI and ADI images obtained with SPHERE-IRDIS spanning 6 years of observations. We reduced PDI datasets through the IRDAP polarimetric data reduction pipeline (for PDI data) and a novel algorithm that we developed (MUSTARD, for ADI data). I will explain the principle of our inverse-problem based MUSTARD algorithm. I will then show the trace of the potential spiral that we inferred by identifying local radial maxima in azimuthal slices of the disc in each dataset. I will then compare the measured traces with the expected motion of a spiral launched by planet c - i.e. in rigid-body motion. I will show how the traces seem to perfectly align in all datasets, and will finally discuss the implications of our results on the nature of this extended feature.

How to cite: Juillard, S., Christiaens, V., Absil, O., and Benisty, M.:  A Spiral arm or a Vortex in the outer disk of PDS-70 ?, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-942,, 2022.

Michael Weber, Barbara Ercolano, and Giovanni Picogna

Disk winds and planet-disk interactions are considered to be two of the most important mechanisms that drive the evolution and dispersal of protoplanetary disks and in turn define the environment in which planets form and evolve. While both have been studied extensively in the past, we combine them into one model by performing three-dimensional radiation-hydrodynamic simulations of planet-hosting disks that are undergoing X-ray photoevaporation, with the goal to analyse the interactions between both mechanisms and to produce synthetic observations of common disk and wind diagnostics that could serve as observational tools for testing the interactions between the planet, the disk and the wind in our models.

The models show that a cavity in the gas disk that is carved by a sufficiently massive planet can significantly affect the structure and kinematics of a photoevaporative wind. This effect can be strong enough to be observable in commonly observed wind diagnostic lines, such as the [OI] 6300 Å or [SII] 6730 Å line, which we model with detailed photoionization calculations. When the disk is observed at inclinations around 40° and higher, the synthetic spectral line profiles may exhibit a peak in the redshifted part of the spectrum, which cannot easily be explained by simple wind models alone. Moreover, massive planets can induce asymmetric substructures within the disk and the photoevaporative wind, giving rise to temporal variations of the line profiles that can be strong enough to be observable on timescales of less than a quarter of the planet's orbital period.


How to cite: Weber, M., Ercolano, B., and Picogna, G.: Modelling the interplay between protoplanetary disks, planets and X-ray photoevaporative winds: Observational diagnostics, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1074,, 2022.

Sierk van Terwisga and Alvaro Hacar

The ability of protoplanetary disks to form planets depends on the evolution of their bulk (dust) mass reservoir. Surveys of nearby star-forming regions have revealed that there is a time dependence on the disk dust mass. In different regions in the Orion molecular clouds, meanwhile, the photoevaporation of disk material by nearby young O-type stars is clearly visible. However, the evolution of disk masses as a function of the FUV radiation field is not usually studied empirically, and its influence around fainter, but more common, B-type stars is not well constrained by observations.

In this contribution we take an empirical view of the impact of external FUV fields on the evolution of protoplanetary disks in Orion, by using existing surveys in the Trapezium and NGC 2024 clusters, and the new N = 873 Survey of Orion Disks with ALMA in L1641 and L1647. Together, these observations allow us to confront model predictions, and provide a constraint on how commonly external photoevaporation determines the evolution of planet-forming material in the first megayears.

How to cite: van Terwisga, S. and Hacar, A.: Protoplanetary disk mass loss near O- and B-type stars: an empirical view, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1142,, 2022.