Periodic Reporting for period 3 - PLAMO (Planet- and Moon-Factory)
Période du rapport: 2024-01-01 au 2025-06-30
This ERC is about how planets and moons are forming within and outside the Solar System. This question is trying to answer one of the most basic questions of humankind: what is our origin. When the first exoplanets were discovered, the first cases were nothing alike the planets we see in the Solar System. Now, we have also 2 exomoons discovered orbiting extrasolar planets, and they are also very different for all the moons in the Solar System. The first 2 exomoons happen to be massive, gaseous objects, similar to a mini version of Neptune. How these very unique moons could have formed is one of the research questions we are addressing. Besides, we still do not understand well the formation of moons around the gaseous planets in the Solar System, as well as the details of formation of our planets. With computer simulations, we try to better understand the planet and moon formation processes, as well as provide observational predictions, how/where these forming systems could be detected with telescopes.
In the first 36 months, we published 9 peer-reviewed papers. On Project 3 (moon formation), we published a paper entitled “An N-body population synthesis framework for the formation of moons around Jupiter-like planets”, led by PhD student Marco Cilibrasi, supervised by the ERC PI. Within this work we presented an N-body population synthesis framework for satellite formation around a Jupiter-like planet. With this improved modeling, we found that only about 15% of the resulting population is more massive than the Galilean one, causing migration rates to be low and resonant captures to be uncommon. In 10% of the cases, moons are engulfed by the planet, and 1 per cent of the satellite-systems lose at least 1 Earth-mass into the planet, contributing only in a minor part to the giant planet's envelope's heavy element content. We examined the differences in outcome between the 1D and 2D disc models and used machine learning techniques (Randomized Dependence Coefficient together with t-SNE) to compare our population with the Galilean system. Detecting our population around known transiting Jupiter-like planets via transits and TTVs would be challenging, but 14% of the moons could be spotted with an instrumental transit sensitivity of 10^-5.
Within Project 2 (observational predictions and disk parameters), we published “Observability of forming planets and their circumplanetary discs - III. Polarized scattered light in near-infrared”, led by the PI. There is growing amount of very high resolution polarized scattered light images of circumstellar disks. Nascent giant planets are surrounded by their own circumplanetary disks that may scatter and polarize both the planetary and stellar light. In this paper, we investigated whether we could detect circumplanetary discs with the same technique and what can we learn from such detections. We created scattered light mock observations at 1.245 microns (J band) for instruments like SPHERE and GPI, for various planetary masses (0.3 1.0 5.0 and 10.0 MJup ). We found that the detection of a circumplanetary disc at 50 au from the star is significantly favoured if the planet is massive ( ≥5MJup ) and the system is nearly face-on (≤30°).
Within project 1 (planet formation), we published 4 papers, two led by doctoral student Fabian Binkert (& supervised by the PI), and one led by the PI. The first one is entitled “First 3D grid-based gas-dust simulations of circumstellar discs with an embedded planet”. Substructures are ubiquitous in high resolution (sub-)millimeter continuum observations of circumstellar disks. We found that all but the Neptune-mass planet open annular gaps in both the gas and the dust component of the disk. We found that the temporal evolution of the dust density distribution is distinctly different from the gas'. For example, the planets cause significant vertical stirring of the dust in the circumstellar disc which opposes the vertical settling. This creates a thicker dust disk than disks without a planet. Comparing the dust disk masses in the 3D simulations to the disk masses derived from the 2D ALMA synthetic images using the optically thin approximation, we find the former to be a factor of a few (up to 10) larger, pointing to the conclusion that real disks are significantly more massive than previously thought based on ALMA continuum images.
The second paper was the continuation of this first work, and entitled “Meridional Circulation of Dust and Gas in the Circumstellar Disk: Delivery of Solids onto the Circumplanetary Region”. We found that the meridional circulation (Szulágyi et al. 2014; Fung & Chiang 2016) drives a strong vertical flow for the dust as well, hence the dust is not settled in the midplane, even for millimeter-sized grains. The meridional circulation will deliver dust and gas vertically onto the circumplanetary region, efficiently bridging over the gap.
The second PhD student, Marco Cilibrasi also published a paper supervised by the PI. Cilibrasi et al. 2023 entitled "Meridional circulation driven by planetary spiral wakes in radiative and magnetized protoplanetary discs". We found that the addition of magnetic field will not change the meridional circulation. We calculated the equivalent turbulent alpha for the planet generated spirals, and it is on the order of 1e-3 alpha, which makes it one of the most important angular momentum loss mechanisms in the circumstellar disk once the planet is formed. This mechanism was not considered before, so it a significant step forward in the field.
Furthermore, the PI was co-author on two additional paper, one being the second ever exomoon detection, which paper was published in Nature Astronomy and had significant media coverage. Kepler-1708 b is a statistically validated Jupiter-sized planet orbiting a Sun-like quiescent star at 1.6 au.
Within Project 2 (observational predictions and disk parameters), we published “Observability of forming planets and their circumplanetary discs - III. Polarized scattered light in near-infrared”, led by the PI. There is growing amount of very high resolution polarized scattered light images of circumstellar disks. Nascent giant planets are surrounded by their own circumplanetary disks that may scatter and polarize both the planetary and stellar light. In this paper, we investigated whether we could detect circumplanetary discs with the same technique and what can we learn from such detections. We created scattered light mock observations at 1.245 microns (J band) for instruments like SPHERE and GPI, for various planetary masses (0.3 1.0 5.0 and 10.0 MJup ). We found that the detection of a circumplanetary disc at 50 au from the star is significantly favoured if the planet is massive ( ≥5MJup ) and the system is nearly face-on (≤30°).
Within project 1 (planet formation), we published 4 papers, two led by doctoral student Fabian Binkert (& supervised by the PI), and one led by the PI. The first one is entitled “First 3D grid-based gas-dust simulations of circumstellar discs with an embedded planet”. Substructures are ubiquitous in high resolution (sub-)millimeter continuum observations of circumstellar disks. We found that all but the Neptune-mass planet open annular gaps in both the gas and the dust component of the disk. We found that the temporal evolution of the dust density distribution is distinctly different from the gas'. For example, the planets cause significant vertical stirring of the dust in the circumstellar disc which opposes the vertical settling. This creates a thicker dust disk than disks without a planet. Comparing the dust disk masses in the 3D simulations to the disk masses derived from the 2D ALMA synthetic images using the optically thin approximation, we find the former to be a factor of a few (up to 10) larger, pointing to the conclusion that real disks are significantly more massive than previously thought based on ALMA continuum images.
The second paper was the continuation of this first work, and entitled “Meridional Circulation of Dust and Gas in the Circumstellar Disk: Delivery of Solids onto the Circumplanetary Region”. We found that the meridional circulation (Szulágyi et al. 2014; Fung & Chiang 2016) drives a strong vertical flow for the dust as well, hence the dust is not settled in the midplane, even for millimeter-sized grains. The meridional circulation will deliver dust and gas vertically onto the circumplanetary region, efficiently bridging over the gap.
The second PhD student, Marco Cilibrasi also published a paper supervised by the PI. Cilibrasi et al. 2023 entitled "Meridional circulation driven by planetary spiral wakes in radiative and magnetized protoplanetary discs". We found that the addition of magnetic field will not change the meridional circulation. We calculated the equivalent turbulent alpha for the planet generated spirals, and it is on the order of 1e-3 alpha, which makes it one of the most important angular momentum loss mechanisms in the circumstellar disk once the planet is formed. This mechanism was not considered before, so it a significant step forward in the field.
Furthermore, the PI was co-author on two additional paper, one being the second ever exomoon detection, which paper was published in Nature Astronomy and had significant media coverage. Kepler-1708 b is a statistically validated Jupiter-sized planet orbiting a Sun-like quiescent star at 1.6 au.
Ongoing projects are confidential, so cannot detail them here. In short, all three projects have ongoing work, that we expect to publish in the future.