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Growing planets interact with their surrounding protoplanetary disc, generating feedback effects that may promote or suppress nearby planet formation. We study how spiral waves launched by planets affect the motion and collisional evolution of particles in the disc. To this end, we perform local 2D hydrodynamical simulations that include a gap-opening planet and integrate particle trajectories within the gas field. Our results show that particle trajectories bend at the location of the spiral wave, and collisions occurring within the spiral exhibit significantly enhanced collisional velocities compared to elsewhere. To quantify this effect, we ran simulations with varying planetary masses and particle sizes. The resulting collisional velocities within the spiral far exceed the typical fragmentation threshold, even for collisions between particles of relatively similar sizes and for planetary masses below the pebble isolation mass. If collisions within the spiral are frequent, this effect could lead to progressively smaller particle sizes as the radial distance from the planet decreases, impacting processes such as gap filtering, pebble accretion, and planetesimal formation. [ABSTRACT FROM AUTHOR]

We examine images of the protoplanetary disk 114–426 with JWST/NIRCam in 12 bands. This large disk is oriented edge on with a dark midplane flanked by lobes of scattered light. The outer edges of the midplane are seen in silhouette against the Orion Nebula, providing a unique opportunity to study planet-forming material in absorption. We discover a dip in the scattered light of the disk at 3 μ m—compelling evidence for the presence of water ice. The 3 μ m dip is also seen in the silhouette of the disk, where we quantify the ice abundance with models of pure absorption and avoid the complications of disk scattering effects. We find grain ice-to-refractory mass ratios of up to ~0.2, maximum grain sizes of 0.25–5 μ m, and a total dust plus ice mass of 0.46 M ⊕ in the silhouette region. We also discover excess absorption in the NIRCam bands that include the Pa α line, suggesting there may be excited atomic hydrogen in the disk. Examining the morphology of the scattered light lobes reveals that they are laterally offset from each other and exhibit a brightness asymmetry that flips with wavelength—both evidence for a tilted inner disk in this system. [ABSTRACT FROM AUTHOR]

Pebble accretion provides new insights into Earth's building blocks and early protoplanetary disk conditions. Here, we show that mixtures of chondritic components : metal grains, chondrules, calcium-aluminum-rich inclusions (CAIs), and amoeboid olivine aggregates (AOAs) match Earth's major element composition (Fe, Ni, Si, Mg, Ca, Al, O) within uncertainties, whereas no combination of chondrites and iron meteorites does. Our best fits also match the ε 54Cr and ε 50Ti values of Earth precisely, whereas the best fits for chondrites, or components with a high proportion of E chondrules, fails to match Earth. In contrast to some previous studies, our best-fitting component mixture is predominantly carbonaceous, rather than enstatite chondrules. It also includes 15 wt% of early-formed refractory inclusions (CAIs + AOAs), which is similar to that found in some C chondrites (CO, CV, CK), but notably higher than NC chondrites. High abundances of refractory materials is lacking in NC chondrites, because they formed after the majority of refractory grains were either drawn into the Sun or incorporated into terrestrial protoplanets via pebble accretion. We show that combinations of Stokes numbers of chondritic components build 0.35–0.7 Earth masses in 2 My in the Hill regime accretion, for a typical pebble column density of 1.2 kg/m2 at 1 au. However, a larger or smaller column density leads to super-Earth or moon-mass bodies, respectively. Our calculations also demonstrate that a few My of pebble accretion with these components yields a total protoplanet mass inside 1 au exceeding the combined masses of Earth, Moon, Venus, and Mercury. Accordingly, we conclude that pebble accretion is a viable mechanism to build Earth and its major element composition from primitive chondritic components within the solar nebula lifetime. [ABSTRACT FROM AUTHOR]

The observations of comet C/2020 T2 (Palomar) were carried out using the 3.4 mm wavelength microwave band before perihelion from 2021 January 22 to July 5 and after perihelion on 2021 July 13. During this period, the comet was located at a heliocentric distance of between |$r_\text{h}$| = 2.840 and 2.055 au. The consecutive long-term monitoring of outgassing of C/2020 T2 was conducted with Purple Mountain Observatory (PMO) 13.7 m telescope and the Institut de RadioAstronomie Millimétrique (IRAM) 30 m telescope in the atmospheric radio window. The hyperfine triplet components of hydrogen cyanide (HCN (1−0) F = 0−1, F = 2−1, and F = 1−1) of the J = 1−0 vibrational ground-state transitions, as the primary tracer of molecular gas, were unambiguously identified in this comet C/2020 T2. Combining all data, we derived the positive signal of line width corresponds to the coma expansion velocity |$v_{\rm exp}$| from |$\sim$| 0.2 to |$\sim$| 0.4 km s |$^{-1}$|⁠. The mean gas molecular production rates of HCN were derived |$Q_{\rm HCN}$| = (2.92 |$\pm$| 0.51) |$\times$| 10 |$^{25}$| molecules s |$^{-1}$| at PMO 13.7 m, and |$Q_{\rm HCN}$| = (6.26 |$\pm$| 1.55) |$\times$| 10 |$^{25}$| molecules s |$^{-1}$| at IRAM 30 m, respectively. Overall, studying the gas composition of the long-period comet revealed abundant information about the missing link between interstellar molecular clouds and the outer regions of a distant protoplanetary accretion disc, and the relationship between amorphous ice sublimation mechanism and heliocentric distance. [ABSTRACT FROM AUTHOR]

A series of hydrothermal diamond anvil cell experiments was conducted to constrain the equilibrium distribution of molecular H 2 between H 2 O-saturated sodium aluminosilicate melts and H 2 O at elevated temperatures (600–800 °C) and pressures (317–1265 MPa). The distribution of H 2 between the silicate liquid and the aqueous fluid was achieved through real-time monitoring of the H-H stretching vibration under in situ conditions using Raman vibrational spectroscopy. Results show that the solubility of H 2 in silicate melts saturated with H 2 O decreases as the temperature increases, with control exerted by the mole fraction of H 2 O in the melt. The dissolution of H 2 in the hydrous silicate melts appears to follow Henrian behavior, resembling that of an inert, neutral non-polar species. To express species solubility as a function of temperature (T in K) an empirical equation was developed: ln K m/f = 11.4 (±1.3) *1000/T (K) − 18.7 (±1.1) where K m/f is the equilibrium constant for the reaction H 2(g) = H 2(melt). This equation was derived by integrating data from the current and prior experimental studies that include silicate melts with varying H 2 O saturation levels. It should be deemed applicable within the temperature range of 600–1450 °C and pressures ranging from 0.3 to 3 GPa. The implications are extended into developing an understanding of the H partitioning between H 2 -rich atmospheres blanketing magma oceans in the early history of planetary bodies. For example, transferring H from primordial atmospheric envelopes to the interior of rocky exoplanets may be less efficient than previously believed, which should be considered in models of volatile retention. Experimental data also suggest that minimal amounts of solar nebula H 2 are likely to dissolve in the molten surface of primitive objects in the protoplanetary disk (∼10−5 to 10−9 mole faction of H 2 in the melt), contradicting the highly reducing conditions observed in chondrule mineral compositions. [ABSTRACT FROM AUTHOR]

Observed infrared (IR) excesses indicate that protoplanetary discs evolve slowly for the majority of their lifetime before losing their near- and mid-IR excesses on short time-scales. Photoevaporation models can explain this 'two-time-scale' nature of disc evolution through the removal of inner regions of discs after a few million years. However, they also predict the existence of a population of non-accreting discs with large cavities. Such discs are scarce within the observed population, suggesting the models are incomplete. We explore whether radiation-pressure-driven outflows are able to remove enough dust to fit observations. We simulate these outflows using cudisc , including dust dynamics, growth/fragmentation, radiative transfer and a parametrization of internal photoevaporation. We find that, in most cases, dust mass-loss rates are around 5–10 times too small to meet observational constraints. Particles are launched from the disc inner rim, however grains larger than around a micron do not escape in the outflow, meaning mass-loss rates are too low for the initial dust masses at gap-opening. Only systems that have smooth photoevaporation profiles with gas mass-loss rates |$\gt \sim$| |$5 \times 10^{-9}$| |$\mathrm{ M}_\odot$| yr |$^{-1}$| and disc dust masses |$\lt \sim$| 1 |$\mathrm{ M}_{\oplus }$| at the time of gap opening can meet observational constraints; in the current models these manifest as EUV winds driven by atypically large high-energy photon fluxes. We also find that the height of the disc's photosphere is controlled by small grains in the outflow as opposed to shadowing from a hot inner rim; the effect of this can be seen in synthetic scattered light observations. [ABSTRACT FROM AUTHOR]

Recent high angular resolution ALMA observations have revealed rich information about protoplanetary discs, including ubiquitous substructures and three-dimensional gas kinematics at different emission layers. One interpretation of these observations is embedded planets. Previous 3D planet–disc interaction studies are either based on viscous simulations or non-ideal magnetohydrodynamics (MHD) simulations with simple prescribed magnetic diffusivities. This study investigates the dynamics of gap formation in 3D non-ideal MHD discs using non-ideal MHD coefficients from the look-up table that is self-consistently calculated based on the thermochemical code. We find a concentration of the poloidal magnetic flux in the planet-opened gap (in agreement with previous work) and enhanced field-matter coupling due to gas depletion, which together enable efficient magnetic braking of the gap material, driving a fast accretion layer significantly displaced from the disc mid-plane. The fast accretion helps deplete the gap further and is expected to negatively impact the planet growth. It also affects the corotation torque by shrinking the region of horseshoe orbits on the trailing side of the planet. Together with the magnetically driven disc wind, the fast accretion layer generates a large, persistent meridional vortex in the gap, which breaks the mirror symmetry of gas kinematics between the top and bottom disc surfaces. Finally, by studying the kinematics at the emission surfaces, we discuss the implications of planets in realistic non-ideal MHD discs on kinematics observations. [ABSTRACT FROM AUTHOR]

Planet formation in the Solar system was started when the first planetesimals were formed from the gravitational collapse of pebble clouds. Numerical simulations of this process, especially in the framework of streaming instability, produce various power laws for the initial mass function for planetesimals. While recent advances have shed light on turbulence and its role in particle clustering, a comprehensive theoretical framework linking turbulence characteristics to particle cluster properties and planetesimal mass function remains incomplete. Recently, a kinetic field theory (KFT) for ensembles of point-like classical particles in or out of equilibrium has been applied to cosmic structure formation. This theory encodes the dynamics of a classical particle ensemble by a generating functional specified by the initial probability distribution of particles in phase space and their equations of motion. Here, we apply KFT to planetesimal formation. A model for the initial probability distribution of dust particles in phase space is obtained from a quasi-initial state for a three-dimensional streaming-instability simulation that is a particle distribution with velocities for gas and particles from the Nakagawa relations. The equations of motion are chosen for the simplest case of freely streaming particles. We calculate the non-linearly evolved density power spectrum of dust particles and find that it develops a universal |$k^{-3}$| tail at small scales, suggesting scale-invariant structure formation below a characteristic and time-dependent length-scale. Thus, the KFT analysis indicates that the initial state for streaming instability simulations does not impose a constraint on structure evolution during planetesimal formation. [ABSTRACT FROM AUTHOR]

In the inner regions of protoplanetary discs, ionization chemistry controls the fluid viscosity, and is thus key to understanding various accretion, outflow and planet formation processes. The ionization is driven by thermal and non-thermal processes in the gas phase, as well as by dust-gas interactions that lead to grain charging and ionic and thermionic emission from grain surfaces. The latter dust–gas interactions are moreover a strong function of the grain size distribution. However, analyses of chemical networks that include ionic/thermionic emission have so far only considered grains of a single size (or only approximately treated the effects of a size distribution), while analyses that include a distribution of grain sizes have ignored ionic/thermionic emission. Here, we (1) investigate a general chemical network, widely applicable in inner disc regions, that includes gas phase reactions, ionic and thermionic emission, and an arbitrary grain size distribution; (2) present a numerical method to solve this network in equilibrium; and (3) elucidate a general method to estimate the chemical time-scale. We show that (a) approximating a grain size distribution by an 'effective dust-to-gas ratio' (as done in previous work) can predict significantly inaccurate grain charges; and (b) grain charging significantly alters grain collisional time-scales in the inner disc. For conditions generally found in the inner disc, this work facilitates (i) calculation of fluid resistivities and viscosity; and (ii) inclusion of the effect of grain charging on grain fragmentation and coagulation (a critical effect that is often ignored). [ABSTRACT FROM AUTHOR]

Accretion and migration usually proceed concurrently for giant planet formation in the natal protoplanetary disks. Recent works indicate that the concurrent accretion onto a giant planet imposes significant impact on the planetary migration dynamics in the isothermal regime. In this work, we carry out a series of 2D global hydrodynamical simulations with Athena++ to explore the effect of thermodynamics on the concurrent accretion and migration processes of the planets in a self-consistent manner. The thermodynamics effect is modeled with a thermal relaxation timescale using a β -cooling prescription. Our results indicate that radiative cooling has a substantial effect on the accretion and migration processes of the planet. As cooling timescales increase, we observe a slight decrease in the planetary accretion rate, and a transition from the outward migrating into inward migration. This transition occurs approximately when the cooling timescale is comparable to the local dynamical timescale ( β ∼ 1 ), which is closely linked to the asymmetric structures from the circumplanetary disk (CPD) region. The asymmetric structures in the CPD region which appear with an efficient cooling provide a strong positive torque driving the planet migrate outward. However, such a positive torque is strongly suppressed, when the CPD structures tend to disappear with a relatively long cooling timescale ( β ≳ 10 ). Our findings may also be relevant to the dynamical evolution of accreting stellar-mass objects embedded in disks around active galactic nuclei. [ABSTRACT FROM AUTHOR]

Accretion of protoplanetary discs (PPDs) could be driven by magnetohydrodynamic disc winds rather than turbulent viscosity. With a dynamical prescription for angular momentum transport induced by disc winds, we perform 2D simulations of PPDs to systematically investigate the rate and direction of planet migration in a windy disc. We find that the the strength of disc winds influences the corotation region similarly to the 'desaturation' effect of viscosity. The magnitude and direction of torque depend sensitively on the hierarchy between the radial advection time-scale across the horseshoe due to disc wind |$\tau _{\rm dw}$|⁠ , the horseshoe libration time-scale |$\tau _{\rm lib}$| and U-turn time-scale |$\tau _{\rm U-turn}$|⁠. Initially, as wind strength increases and the advection time-scale shortens, a non-linear horseshoe drag emerges when |$\tau _{\rm dw} \lesssim \tau _{\rm lib}$|⁠ , which tends to drive strong outward migration. Subsequently, the drag becomes linear and planets typically still migrate inward when |$\tau _{\rm dw} \lesssim \tau _{\rm U-turn} \sim \tau _{\rm lib}h$|⁠ , where h is the disc aspect ratio. For a planet with mass ratio of |${\sim} 10^{-5}$|⁠ , the zone of outward migration sandwiched between inner and outer inward migration zones corresponds to |$\sim$| 10–100 au in a PPD with accretion rates between |$10^{-8}$| and |$10^{-7}\, \mathrm{ M}_\odot \text{yr}^{-1}$|⁠. [ABSTRACT FROM AUTHOR]

This work investigated the dynamics of planets in binary systems and provided insights into the stability and evolution of these systems. We explored the influence of a nearby secondary star on planetary growth and evolution, focusing on S -type configurations. We tracked the orbits of the planets and analysed their stability over long time-scales, considering various parameters such as mass, eccentricity, and inclination. Our results show that the presence of a secondary star can significantly impact the growth and evolution of planets, leading to changes in their orbits and potential ejection from the system, however, it was possible to identify stable planets even in systems experiencing multiple disturbances. One of the most significant results of the work was the analysis of the increased material in the disc near the primary star, which contributes to planet growth, driven by the density spirals influenced by the binary star. These findings have important implications for the search for habitable exoplanets and emphasize the need for further studies of planetary systems in binary star environments. [ABSTRACT FROM AUTHOR]

The alignment of non‐spherical “flattened” chondrules into a petrofabric is a common feature of hydrated carbonaceous chondrite meteorites. This texture can form as a result of impacts at peak shock pressures exceeding 10 GPa. However, many carbonaceous chondrites with petrofabrics are unshocked. While several processes have been proposed to explain this incongruency, including erasure of shock effects by alteration (both aqueous and thermal), none have yet been confirmed. Kolang is a brecciated Mighei‐like carbonaceous chondrite wherein analysis of chondrule shape and orientation shows that it has a pronounced petrofabric defined by elongate chondrules that is shared between clasts with differing aqueous and thermal alteration histories. Its petrofabric, therefore, must have developed after the altered clasts had been juxtaposed; any sign of shock associated with impact‐driven deformation cannot have been erased. We have investigated the shock experienced by Kolang with a combination of traditional optical methods and electron backscatter diffraction. We find that the peak shock pressure experienced by Kolang was likely ~4–5 GPa, too low to generate an impact‐induced petrofabric. Kolang has not experienced sufficient shock, whether by a single or multiple impacts, to deform its chondrules from spheres into elongate chondrules. The most likely explanation, therefore, is that Kolang accreted elongate chondrules that were aligned under relatively low pressure. [ABSTRACT FROM AUTHOR]

It has been proposed, and confirmed by multiple observations, that disks around low-mass stars display a molecule-rich emission and carbon-rich disk chemistry as compared to their hotter, more massive solar counterparts. In this work, we present JWST Disk Infrared Spectral Chemistry Survey MIRI-MRS observations of the solar-mass star DoAr 33, a low-accretion rate T Tauri star showing an exceptional carbon-rich inner disk. We report detections of H2O, OH, and CO2, as well as the more complex hydrocarbons, C2H2 and C4H2. Through the use of thermochemical models, we explore different spatial distributions of carbon and oxygen across the inner disk and compare the column densities and temperatures obtained from LTE slab model retrievals. We find the best match to the observed column densities with models that have carbon enrichment, and the retrieved emitting temperature and area of C2H2 with models that have C/O = 2–4 inside the 500 K carbon-rich dust sublimation line. This suggests that the origin of the carbon-rich chemistry is likely due to the sublimation of carbon-rich grains near the soot line. This would be consistent with the presence of dust processing as indicated by the detection of crystalline silicates. We propose that this long-lived hydrocarbon-rich chemistry observed around a solar-mass star is a consequence of the unusually low M-star-like accretion rate of the central star, which lengthens the radial mixing timescale of the inner disk, allowing the chemistry powered by carbon grain destruction to linger. [ABSTRACT FROM AUTHOR]

We analyze near-infrared integral field spectropolarimetry of the AB Aurigae protoplanetary disk and protoplanet (AB Aur b), obtained with SCExAO/CHARIS in 22 wavelength channels covering the J, H, and K passbands (λ 0 = 1.1–2.4 μ m) over angular separations of ρ ≈ 0.″13 to 1.″1 (∼20–175 au). Our images resolve spiral structures in the disk in each CHARIS channel. At the longest wavelengths, the data may reveal an extension of the western spiral seen in previous polarimetric data at ρ < 0.″3 out to larger distances clockwise from the protoplanet AB Aur b, coincident with the Atacama Large Millimeter/submillimeter Array–detected CO gas spiral. While AB Aur b is detectable in complementary total intensity data, it is a nondetection in polarized light at λ > 1.3 μ m. While the observed disk color is extremely red across JHK, the disk has a blue intrinsic scattering color consistent with small dust grains. The disk's polarization spectrum is redder than AB Aur b's total intensity spectrum. The polarization fraction peaks at ∼0.6 along the major disk axis. Radiative transfer modeling of the CHARIS data shows that small, porous dust grains with a porosity of p = 0.6–0.8 better reproduce the scattered-light appearance of the disk than more compact spheres (p = 0.3), especially the polarization fraction. This work demonstrates the utility of integral field spectropolarimetry to characterize structures in protoplanetary disks and elucidate the properties of the disks' dust. [ABSTRACT FROM AUTHOR]

Volatiles like H2O are present as ice in solids in the cold outer regions of protoplanetary disks and as vapor in the warm inner regions within the water snow line. Icy pebbles drifting inwards from the outer disk sublimate after crossing the snow line, enriching the inner disk with solid mass and water vapor. Meanwhile, protoplanets forming within the disk open gaps in the disk gas, creating traps against the inward drift of pebbles and in turn reducing water enrichment in the inner disk. Recent disk observations from millimeter interferometry and infrared spectroscopy have supported this broad picture by finding a correlation between the outer radial distribution of pebbles and the properties of inner water vapor spectra. In this work, we aim at further informing previous and future observations by building on previous models to explore pebble drift in disks with multiple gaps. We systematically explore multiple gap locations and their depths (equivalent to the specific masses of planets forming within), and different particle sizes to study their impact on inner disk water enrichment. We find that the presence of close-in deep gaps carved by a Jupiter-mass planet is likely crucial for blocking icy pebble delivery into the inner disk, while planets with lower masses only provide leaky traps. We also find that disks with multiple gaps show lower vapor enrichment in the inner disk. Altogether, these model results support the idea that inner disk water delivery and planet formation are regulated by the mass and location of the most massive planets. [ABSTRACT FROM AUTHOR]

Recent research provides compelling evidence that the decay of short-lived radioisotopes (SLRs), such as 26Al, provided the bulk of energy for heating and desiccation of volatile-rich planetesimals in the early solar system. However, it remains unclear whether the early solar system was highly enriched relative to other planetary systems with similar formation characteristics. While the solar system possesses an elevated level of SLR enrichment compared to the interstellar medium, determining SLR enrichment of individual protoplanetary disks observationally has not been performed and is markedly more difficult. We use N -body simulations to estimate enrichment of SLRs in star-forming regions through two likely important SLR sources: stellar winds from massive stars and supernovae (SNae). We vary the number of stars and the radii of the star-forming regions and implement two models of stellar-wind SLR propagation for the radioisotopes 26Al and 60Fe. We find that for 26Al enrichment the solar system is at the upper end of the expected distribution, while for the more SNae-dependent isotope 60Fe we find that the solar system is comparatively very highly enriched. Furthermore, combined with our previous research, these results suggest that the statistical role of 26Al-driven desiccation on exoplanet bulk composition may be underestimated in typical interpretations of the low-mass exoplanet census, and that 60Fe is even less influential as a source of heating than previously assumed. [ABSTRACT FROM AUTHOR]

Computer modeling has shown that, during the collisional evolution of a solid-state component in gas–dust protoplanetary disks, porous dust clusters of widely ranging sizes are formed. Clusters of this kind have a well-developed internal structure that is topologically similar to the structure of porous catalysts, adsorbents, and carriers used in the organic synthesis technology. On the other hand, observational data currently obtained by such instruments as the Atacama Large Millimeter/submillimeter Array (ALMA) show that complex preorganic compounds rather than only water and volatiles are present in protoplanetary disks. This suggests the possibility that, in protoplanetary disks, there are mechanisms of capturing complex chemical compounds by porous dust clusters and transporting these compounds to warmer regions during migration. When getting to warmer regions of protoplanetary disks, dust clusters undergo a change in the pore space, which may increase the surface holding the captured compounds and, hence, intensify their reactivity. [ABSTRACT FROM AUTHOR]

Understanding the material transport and mixing processes in the Solar protoplanetary disk provides important constraints on the origin of chemical and isotopic diversities of our planets. The limited extent of radial transport and mixing between the inner and outer Solar System has been suggested based on a fundamental isotopic dichotomy between non‐carbonaceous (NC) and carbonaceous (CC) meteorite groups. The limited transport and mixing could be further tested by tracing the formation regions of individual meteoritic components, such as Ca‐Al‐rich inclusions (CAIs) and chondrules. Here, we show further evidence for the outward transport of CAIs and chondrules from the inner and subsequent thermal processing in the outer region of the protoplanetary disk based on the petrography and combined Cr‐Ti‐O isotope systematics of chondrules from the Vigarano‐like (CV) carbonaceous chondrite Allende. One chondrule studied consists of an olivine core that exhibits NC‐like Ti and O, but CC‐like Cr isotopic signatures, which is enclosed by a pyroxene igneous rim with CC‐like O isotope ratios. These observations indicate that the olivine core formed in the inner Solar System. The olivine core then migrated into the outer Solar System and experienced nebular thermal processing that generated the pyroxene igneous rim. The nebular thermal processing would result in Cr isotope exchange between the olivine core and CC‐like materials, but secondary alteration effects on the parent body are also responsible for the CC‐like Cr isotope signature. By combining previously reported Cr‐Ti‐O isotope systematics of CV chondrules, we show that some CV chondrules larger than ~1 mm would have formed in the inner Solar System. The accretion of the millimeter‐sized, inner Solar System solids onto the CV carbonaceous chondrite parent body would require their very early migration into the outer Solar System within the first 1 million years after the Solar System formation. [ABSTRACT FROM AUTHOR]

We provide an overview of the isotopic signatures of presolar supernova grains, specifically focusing on 44Ti-containing grains with robustly inferred supernova origins and their implications for nucleosynthesis and mixing mechanisms in supernovae. Recent technique advancements have enabled the differentiation between radiogenic (from 44Ti decay) and nonradiogenic 44Ca excesses in presolar grains, made possible by enhanced spatial resolution of Ca-Ti isotope analyses with the Cameca NanoSIMS (Nano-scale Secondary Ion Mass Spectrometer) instrument. Within the context of presolar supernova grain data, we discuss (i) the production of 44Ti in supernovae and the impact of interstellar medium heterogeneities on the galactic chemical evolution of 44Ca/40Ca, (ii) the nucleosynthesis processes of neutron bursts and explosive H-burning in Type II supernovae, and (iii) challenges in identifying the progenitor supernovae for 54Cr-rich presolar nanospinel grains. Drawing on constraints and insights derived from presolar supernova grain data, we also provide an overview of our current understanding of the roles played by various supernova types – including Type II, Type Ia, and electron capture supernovae – in accounting for the diverse array of nucleosynthetic isotopic variations identified in bulk meteorites and meteoritic components. We briefly overview the potential mechanisms that have been proposed to explain these nucleosynthetic variations by describing the transport and distribution of presolar dust carriers in the protoplanetary disk. We highlight existing controversies in the interpretation of presolar grain data and meteoritic nucleosynthetic isotopic variations, while also outlining potential directions for future research. [ABSTRACT FROM AUTHOR]

The streaming instability (SI) is currently the leading candidate for triggering planetesimal formation in protoplanetary disks. Recently, a novel variation, the "azimuthal-drift" streaming instability (AdSI), was discovered in disks exhibiting laminar gas accretion. Unlike the classical SI, the AdSI does not require pressure gradients and can concentrate dust even at low abundances. We extend previous simulations of the AdSI to explore the impact of dust abundance, accretion-flow strength, pressure gradients, and grain size. For a dimensionless accretion-flow strength α M = 0.1 and particle Stokes number St = 0.1, we find the AdSI produces dust filaments for initial dust-to-gas ratios as low as ϵ = 0.01. For ϵ ≳ 1, maximum dust-to-gas ratios of order 100 are attained, which can be expected to undergo gravitational collapse. Furthermore, even in systems dominated by the classical SI, an accretion flow drives filament formation, without which the disk remains in a state of small-scale turbulence. Our results suggest that an underlying accretion flow facilitates dust concentration and may thus promote planetesimal formation. [ABSTRACT FROM AUTHOR]

In the early stages of planetary system formation, young exoplanets gravitationally interact with their surrounding environments and leave observable signatures on protoplanetary disks. Among these structures, a pair of nearly symmetric spiral arms can be driven by a giant protoplanet. For the double-spiraled SAO 206462 protoplanetary disk, we obtained three epochs of observations spanning 7 yr using the Very Large Telescope's SPHERE instrument in near-infrared J-band polarized light. By jointly measuring the motion of the two spirals at three epochs, we obtained a rotation rate of − 0. ° 85 ± 0. ° 05 yr − 1 . This rate corresponds to a protoplanet at 66 ± 3 au on a circular orbit dynamically driving both spirals. The derived location agrees with the gap in ALMA dust-continuum observations, indicating that the spiral driver may also carve the observed gap. What is more, a dust filament at ∼63 au observed by ALMA coincides with the predicted orbit of the spiral-arm-driving protoplanet. This double-spiraled system is an ideal target for protoplanet imaging. [ABSTRACT FROM AUTHOR]

Correctly modelling the absorptive properties of dust and haze particles is of great importance for determining the abundance of solid matter within protoplanetary discs and planetary atmospheres. Rigorous analyses such as the discrete dipole approximation (DDA) can be used to obtain accurate absorption cross-sections, but these require significant computing time and are often impractical to use in models. A simple analytical equation exists for spherical particles in the long-wavelength limit (where the wavelength is much larger than the size of the dust particle), but we demonstrate that this can significantly underestimate the absorption. This effect is found to depend strongly on refractive index, with values of |$m=1+11$| i corresponding to an underestimate in absorption by a factor of 1000. Here we present MANTA-Ray (modified absorption of non-spherical tiny aggregates in the RAYleigh regime): a simple model that can calculate absorption efficiencies within 10–20 per cent of the values predicted by DDA, but |$10^{13}$| times faster. MANTA-Ray is very versatile and works for any wavelength and particle size in the long wavelength regime. It is also very flexible with regards to particle shape, and can correctly model structures ranging from long linear chains to tight compact clusters, composed of any material with refractive index 1 + 0.01i |$\le m \le$| 11 + 11i. The packaged model is provided as publicly available code for use by the astrophysical community. [ABSTRACT FROM AUTHOR]

Modeling environments that are not in local thermal equilibrium, such as protoplanetary disks or planetary atmospheres, with molecular spectroscopic data from space telescopes requires knowledge of the rate coefficients of rovibrationally inelastic molecular collisions. Here, we present such rate coefficients in a temperature range from 10 to 500 K for collisions of CO2 with He atoms in which CO2 is (de)excited in the bend mode. They are obtained from numerically exact coupled-channel (CC) calculations as well as from calculations with the less demanding coupled-states approximation (CSA) and the vibrational close-coupling rotational infinite-order sudden (VCC-IOS) method. All of the calculations are based on a newly calculated accurate ab initio four-dimensional CO2–He potential surface including the CO2 bend (ν2) mode. We find that the rovibrationally inelastic collision cross sections and rate coefficients from the CSA and VCC-IOS calculations agree to within 50% with the CC results at the rotational state-to-state level, except for the smaller ones and in the low energy resonance region, and to within 20% for the overall vibrational quenching rates except for temperatures below 50 K where resonances provide a substantial contribution. Our CC quenching rates agree with the most recent experimental data within the error bars. We also compared our results with data from Clary et al. calculated in the 1980s with the CSA [A. J. Banks and D. C. Clary, J. Chem. Phys. 86, 802 (1987)] and VCC-IOS [D. C. Clary, J. Chem. Phys. 78, 4915 (1983)] methods and a simple atom-atom model potential based on ab initio Hartree–Fock calculations and found that their cross sections agree fairly well with ours for collision energies above 500 cm−1, but that the inclusion of long range attractive dispersion interactions is crucial to obtain reliable cross sections at lower energies and rate coefficients at lower temperatures. [ABSTRACT FROM AUTHOR]

Millimeter emitting dust grains have sizes that make them susceptible to drift in protoplanetary disks due to the difference between their orbital speed and that of the gas. The characteristic drift timescale depends on the surface density of the gas. By comparing disk radius measurements from Atacama Large Millimeter/submillimeter Array CO and continuum observations at millimeter wavelengths, the gas surface density profile and dust drift time can be self-consistently determined. We find that profiles which match the measured dust mass have very short drift timescales, an order of magnitude or more shorter than the stellar age, whereas profiles for disks that are on the cusp of gravitational instability, defined via the minimum value of the Toomre parameter, Q min ∼ 1 − 2 , have drift timescales comparable to the stellar lifetime. This holds for disks with masses of dust ≳5 M ⊕ across a range of absolute ages from less than 1 Myr to over 10 Myr. The inferred disk masses scale with stellar mass as M disk ≈ M * / 5 Q min . This interpretation of the gas and dust disk sizes simultaneously solves two long standing issues regarding the dust lifetime and exoplanet mass budget, and suggests that we consider millimeter wavelength observations as a window into an underlying population of particles with a wide size distribution in secular evolution with a massive planetesimal disk. [ABSTRACT FROM AUTHOR]

We demonstrate that shadows cast on a protoplanetary disk can drive it eccentric. Stellar irradiation dominates heating across much of these disks, so an uneven illumination can have interesting dynamical effects. Here, we focus on transition disks. We carry out 3D Athena++ simulations, using a constant thermal relaxation time to describe the disk's response to changing stellar illumination. We find that an asymmetric shadow, a feature commonly observed in real disks, perturbs the radial pressure gradient and distorts the fluid streamlines into a set of twisted ellipses. Interactions between these streamlines have a range of consequences. For a narrow ring, an asymmetric shadow can sharply truncate its inner edge, possibly explaining the steep density drop-offs observed in some disks and obviating the need for massive perturbers. For a wide ring, such a shadow can dismantle it into two (or possibly more) eccentric rings. These rings continuously exert torque on each other and drive gas accretion at a healthy rate, even in the absence of disk viscosity. Signatures of such twisted eccentric rings may have already been observed as, e.g., twisted velocity maps inside gas cavities. We advocate for more targeted observations and for a better understanding on the origin of such shadows. [ABSTRACT FROM AUTHOR]

Planet–disk interactions can produce kinematic signatures in protoplanetary disks. While recent observations have detected non-Keplerian gas motions in disks, their origins are still being debated. To explore this, we conduct 3D hydrodynamic simulations using the code FARGO3D to study nonaxisymmetric kinematic perturbations at two scale heights induced by Jovian planets in protoplanetary disks, followed by examinations of detectable signals in synthetic CO emission line observations at millimeter wavelengths. We advocate for using residual velocity or channel maps, generated by subtracting an azimuthally averaged background of the disk, to identify planet-induced kinematic perturbations. We investigate the effects of two basic simulation parameters, simulation duration and numerical resolution, on the simulation results. Our findings suggest that a short simulation (e.g., 100 orbits) is insufficient to establish a steady velocity pattern given our chosen viscosity (α = 10−3) and displays plenty of fluctuations on an orbital timescale. Such transient features could be detected in observations. By contrast, a long simulation (e.g., 1000 orbits) is required to reach steady state in kinematic structures. At 1000 orbits, the strongest detectable velocity structures are found in the spiral wakes close to the planet. Through numerical convergence tests, we find hydrodynamics results converge in spiral regions at a resolution of 14 cells per disk scale height or higher. Meanwhile, synthetic observations produced from hydrodynamic simulations at different resolutions are indistinguishable with 0.″1 angular resolution and 10 hr of integration time on Atacama Large Millimeter/submillimeter Array. [ABSTRACT FROM AUTHOR]

X-rays have significant impacts on cold, weakly ionized protoplanetary disks by increasing the ionization rate and driving chemical reactions. Stellar flares are explosions that emit intense X-rays and are the unique source of hard X-rays with an energy of ≳10 keV in the protoplanetary disk systems. Hard X-rays should be carefully taken into account in models as they can reach the disk midplane as a result of scattering in the disk atmospheres. However, previous models are insufficient to predict the hard X-ray spectra because of simplifications in flare models. We develop a model of X-ray spectra of stellar flares based on observations and flare theories. The flare temperature and nonthermal electron emissions are modeled as functions of flare energy, which allows us to better predict the hard X-ray photon flux than before. Using our X-ray model, we conduct radiative transfer calculations to investigate the impact of flare hard X-rays on disk ionization, with a particular focus on the protoplanetary disk around a T Tauri star. We demonstrate that for a flare with an energy of 1035 erg, X-ray photons with ≳5 keV increase the ionization rates more than galactic cosmic rays down to z ≈ 0.1 R. The contribution of flare X-rays to the ionization at the midplane depends on the disk parameters such as disk mass and dust settling. We also find that the 10 yr averaged X-rays from multiple flares could certainly contribute to the ionization. These results emphasize the importance of stellar flares on the disk evolution. [ABSTRACT FROM AUTHOR]

We investigate the formation of dust traffic jams in polar-aligning circumbinary discs. In our first paper, we found as the circumbinary disc evolves towards a polar configuration perpendicular to the binary orbital plane, the differential precession between the gas and dust components leads to multiple dust traffic jams. These dust traffic jams evolve to form a coherent dust ring. In part two, we use 3D smoothed particle hydrodynamical simulations of gas and dust to model an initially highly misaligned circumbinary disc around the 99 Herculis (99 Her) binary system. Our results reveal that the formation of these dust rings is observed across various disc parameters, including the disc aspect ratio, viscosity, surface density power-law index, and temperature power-law index. The dust traffic jams are long-lived and persist even when the disc is fully aligned polar. The midplane dust-to-gas ratio within the rings can surpass unity, which may be a favourable environment for planetesimal formation. Using 2D inviscid shearing box calculations with parameters from our 3D simulations, we find streaming instability modes with significant growth rates. The streaming instability growth time-scale is less than the tilt oscillation time-scale during the alignment process. Therefore, the dust ring will survive once the gas disc aligns polar, suggesting that the streaming instability may aid in forming polar planets around 99 Her. [ABSTRACT FROM AUTHOR]

The composition of a planet's atmosphere is intricately linked to the chemical makeup of the protoplanetary disc in which it formed. Determining the elemental abundances from key volatiles within discs is therefore essential for establishing connections between the composition of discs and planets. The disc around the Herbig Ae star HD 169142 is a compelling target for such a study due to its molecule-rich nature and the presence of a newly forming planet between two prominent dust rings. In this work, we probe the chemistry of the HD 169142 disc at small spatial scales, drawing links between the composition of the disc and the planet-accreted gas. Using thermochemical models and archival data, we constrain the elemental abundances of volatile carbon, oxygen, and sulfur. Carbon and oxygen are only moderately depleted from the gas phase relative to their interstellar abundances, with the inner ~60 au appearing enriched in volatile oxygen. The carbon-to-oxygen ratio is approximately solar within the inner disc (~0.5) and rises above this in the outer disc (>0.5), as expected across the H |$_2$| O snowline. The gas-phase sulfur abundance is depleted by a factor of ~1000, consistent with a number of other protoplanetary discs. Interestingly, the observed SiS emission near the HD 169142 b protoplanet vastly exceeds chemical model predictions, supporting previous hypotheses suggesting its origin in shocked gas or a localized outflow. We contextualize our findings in terms of the potential atmospheric composition of the embedded planet, and highlight the utility of sulfur-bearing molecules as probes of protoplanetary disc chemistry. [ABSTRACT FROM AUTHOR]

The main hurdle of planet formation theory is the metre-scale barrier. One of the most promising ways to overcome it is via the streaming instability (SI). Unfortunately, the mechanism responsible for the onset of this instability remains mysterious. It has recently been shown that the SI is a Resonant Drag Instability (RDI) involving inertial waves. We build on this insight and clarify the physical picture of how the SI develops, while bolstering this picture with transparent mathematics. Like all RDIs, the SI is built on a feedback loop: in the 'forward action', an inertial wave concentrates dust into clumps; in the 'backward reaction', those drifting dust clumps excite an inertial wave. Each process breaks into two mechanisms, a fast one and a slow one. At resonance, each forward mechanism can couple with a backward mechanism to close a feedback loop. Unfortunately, the fast-fast loop is stable, so the SI uses the fast-slow and slow-fast loops. Despite this last layer of complexity, we hope that our explanation will help understand how the SI works, in which conditions it can grow, how it manifests itself, and how it saturates. [ABSTRACT FROM AUTHOR]

Recent (sub)millimetre polarization observations of protoplanetary discs reveal toroidally aligned, effectively prolate dust grains large enough (at least |$\sim 100$| |$\mu$| m) to efficiently scatter millimetre light. The alignment mechanism for these grains remains unclear. We explore the possibility that gas drag aligns grains through gas–dust relative motion when the grain's centre of mass is offset from its geometric centre, analogous to a badminton birdie's alignment in flight. A simple grain model of two non-identical spheres illustrates how a grain undergoes damped oscillations from flow-induced restoring torques which align its geometric centre in the flow direction relative to its centre of mass. Assuming specular reflection and subsonic flow, we derive an analytical equation of motion for spheroids where the centre of mass can be shifted away from the spheroid's geometric centre. We show that a prolate or an oblate grain can be aligned with the long axis parallel to the gas flow when the centre of mass is shifted along that axis. Both scenarios can explain the required effectively prolate grains inferred from observations. Application to a simple disc model shows that the alignment time-scales are shorter than or comparable to the orbital time. The grain alignment direction in a disc depends on the disc (sub-)structure and grain Stokes number (St) with azimuthal alignment for large St grains in sub-Keplerian smooth gas discs and for small St grains near the gas pressure extrema, such as rings and gaps. [ABSTRACT FROM AUTHOR]

Estimates of the frequency of planetary systems in the Milky Way are observationally limited by the low-mass planet regime. Nevertheless, substantial evidence for systems with undetectably low planetary masses now exists in the form of main-sequence stars that host debris discs, as well as metal-polluted white dwarfs. Further, low-mass sections of star formation regions impose upper bounds on protoplanetary disc masses, limiting the capacity for terrestrial or larger planets to form. Here, we use planetary population synthesis calculations to investigate the conditions that allow planetary systems to form only minor planets and smaller detritus. We simulate the accretional, collisional, and migratory growth of |$10^{17}$|  kg embryonic seeds and then quantify which configurations with entirely sub-Earth-mass bodies (⁠|$\lesssim\!\! 10^{24}$|  kg) survive. We find that substantial regions of the initial parameter space allow for sub-terrestrial configurations to form, with the success rate most closely tied to the initial dust mass. Total dust mass budgets of up to |$10^2 \ \mathrm{ M}_{\oplus }$| within 10 au can be insufficiently high to form terrestrial or giant planets, resulting in systems with only minor planets. Consequently, the prevalence of planetary systems throughout the Milky Way might be higher than what is typically assumed, and minor planet-only systems may help inform the currently uncertain correspondence between planet-hosting white dwarfs and metal-polluted white dwarfs. [ABSTRACT FROM AUTHOR]

M dwarf stars are the most promising hosts for detection and characterization of small and potentially habitable planets, and provide leverage relative to solar-type stars to test models of planet formation and evolution. Using Gaia astrometry, adaptive optics imaging, and calibrated gyrochronologic relations to estimate stellar properties and filter binaries, we refined the radii of 117 Kepler objects of interest (confirmed or candidate planets) transiting 74 single late K-type and early M-type stars, and assigned stellar rotation-based ages to 113 of these. We constructed the radius distribution of 115 small (⁠|${\lt} 4\, {\rm R}_{\rm{\oplus}}$|⁠) planets and assessed their evolution. As for solar-type stars, the inferred distribution contains distinct populations of 'super-Earths' (at |${\sim} 1.3 \, {\rm R}_{\rm{\oplus}}$|⁠) and 'sub-Neptunes' (at |${\sim} 2.2 \, {\rm R}_{\rm{\oplus}}$|⁠) separated by a gap or 'valley' at |${\approx} 1.7 \, {\rm R}_{\rm{\oplus}}$| that has a period dependence that is significantly weaker (power-law index of −0.03 |$^{+0.01}_{-0.03}$|⁠) than for solar-type stars. Sub-Neptunes are largely absent at short periods (⁠|${\lt} 2 \, {\rm d}$|⁠) and high irradiance, a feature analogous to the 'Neptune desert' observed around solar-type stars. The relative number of sub-Neptunes to super-Earths declines between the younger and older halves of the sample (median age 3.86 Gyr), although the formal significance is low (⁠|$p = 0.08$|⁠) because of the small sample size. The decline in sub-Neptunes appears to be more pronounced on wider orbits and low stellar irradiance. This is not due to detection bias and suggests a role for H2O as steam in inflating the radii of sub-Neptunes and/or regulating the escape of H/He from them. [ABSTRACT FROM AUTHOR]

Quasi-Keplerian flow, a special regime of Taylor–Couette co-rotating flow, is of great astrophysical interest for studying angular momentum transport in accretion disks. The well-known magnetorotational instability (MRI) successfully explains the flow instability and generation of turbulence in certain accretion disks, but fails to account for these phenomena in protoplanetary disks where magnetic effects are negligible. Given the intrinsic decrease of the temperature in these disks, we examine the effect of radial thermal stratification on three-dimensional global disturbances in linearised quasi-Keplerian flows under radial gravitational acceleration mimicking stellar gravity. Our results show a thermo-hydrodynamic linear instability for both axisymmetric and non-axisymmetric modes across a broad parameter space of the thermally stratified quasi-Keplerian flow. Generally, a decreasing Richardson or Prandtl number stabilises the flow, while a reduced radius ratio destabilises it. This work also provides a quantitative characterisation of the instability. At low Prandtl numbers $Pr$ , we observe a scaling relation of the linear critical Taylor number $Ta_c\propto Pr^{-6/5}$. Extrapolating the observed scaling to high $Ta$ and low $Pr$ may suggest the relevance of the instability to accretion disks. Moreover, even slight thermal stratification, characterised by a low Richardson number, can trigger the flow instability with a small axial wavelength. These findings are qualitatively consistent with the results from a traditional local stability analysis based on short wave approximations. Our study refines the thermally induced linearly unstable transition route in protoplanetary disks to explain angular momentum transport in dead zones where MRI is ineffective. [ABSTRACT FROM AUTHOR]

Planet formation is strongly influenced by the composition and distribution of volatiles within protoplanetary disks. With JWST, it is now possible to obtain direct observational constraints on disk ices, as recently demonstrated by the detection of ice absorption features toward the edge-on HH 48 NE disk as part of the Ice Age Early Release Science program. Here, we introduce a new radiative transfer modeling framework designed to retrieve the composition and mixing status of disk ices using their band profiles, and apply it to interpret the H2O, CO2, and CO ice bands observed toward the HH 48 NE disk. We show that the ices are largely present as mixtures, with strong evidence for CO trapping in both H2O and CO2 ice. The HH 48 NE disk ice composition (pure versus polar versus apolar fractions) is markedly different from earlier protostellar stages, implying thermal and/or chemical reprocessing during the formation or evolution of the disk. We infer low ice-phase C/O ratios around 0.1 throughout the disk, and also demonstrate that the mixing and entrapment of disk ices can dramatically affect the radial dependence of the C/O ratio. It is therefore imperative that realistic disk ice compositions are considered when comparing planetary compositions with potential formation scenarios, which will fortunately be possible for an increasing number of disks with JWST. [ABSTRACT FROM AUTHOR]

We have used the multiobject mode of the Near-Infrared Spectrograph (NIRSpec) on board the James Webb Space Telescope (JWST) to obtain low-resolution 1–5 μ m spectra of 22 brown dwarf candidates in the Orion Nebula Cluster, which were selected with archival images from the Hubble Space Telescope. One of the targets was previously classified as a Herbig–Haro (HH) object and exhibits strong emission in H i, H2, and the fundamental band of CO, further demonstrating that HH objects can have bright emission in that CO band. The remaining targets have late spectral types (M6.5 to early L) and are young based on gravity-sensitive features, as expected for low-mass members of the cluster. According to theoretical evolutionary models, these objects should have masses that range from the hydrogen burning limit to 0.003–0.007 M ⊙. Two of the NIRSpec targets were identified as proplyds in earlier analysis of Hubble images. They have spectral types of M6.5 and M7.5, making them two of the coolest and least massive known proplyds. Another brown dwarf shows absorption bands at 3–5 μ m from ices containing H2O, CO2, OCN−, and CO, indicating that it is either an edge-on class II system or a class I protostar. It is the coolest and least massive object that has detections of these ice features. In addition, it appears to be the first candidate for a protostellar brown dwarf that has spectroscopy confirming its late spectral type. [ABSTRACT FROM AUTHOR]

In the paper, a model for simulating the non-stationary thermal structure of protoplanetary disk in axial symmetry has been provided. The model has been based on the widely used approach of splitting the radiation field into stellar and intrinsic thermal radiation of the medium. The heating by stellar radiation has been calculated by the ray tracing method while the well-known diffusion approximation with a flux limiter (FLD approach) has been used to treat the thermal radiation. To solve the resulting system of linear equations, a modification to Gauss method has been proposed, which has made it possible to speed up the calculations by a factor of ten compared to the widely adopted GMRES method. This model has been used to calculate the steady-state thermal structure of two disks, including those with the parameters of the EX Lup system. A detailed analysis of the simulation results has been performed. Comparison with the results of more accurate methods has made it possible to identify the main shortcomings of the model related to the ignoring of light scattering and to the diffusion nature of the FLD approximation. It has been shown that the disk thermal structure calculated with the FLD approximation has evolved according to analytical estimates of the characteristic thermal time. [ABSTRACT FROM AUTHOR]

Context. Growing evidence suggests that protoplanetary discs may be influenced by late stage infall from the interstellar medium (ISM). It remains unclear the degree to which infall shapes disc populations at ages ≳1 Myr. Aims. We explored possible spatial correlations between stellar accretion rates in the Lupus star-forming region, which would support the hypothesis that infall can regulate stellar accretion. Methods. We considered both the 'clustered' stars towards the centre of Lupus 3, and the 'distributed' stars that are more sparsely distributed across the Lupus complex. We took the observed accretion rates in the literature and explore spatial correlations. In particular, we tested whether the clustered stars exhibit a radial gradient in normalised accretion rates, and whether the distributed stars have spatially correlated accretion rates. Results. We found statistically significant correlations for both the clustered and distributed samples. The clustered sample exhibits higher accretion rates in the central region, consistent with the expected Bondi-Hoyle-Lyttleton accretion rate. Stars that are spatially closer among the distributed population also exhibit more similar accretion rates. These results cannot be explained by the stellar mass distribution for either sample. Age gradients are disfavoured, though not discounted, because normalised disc dust masses are not spatially correlated across the region. Conclusions. Spatially correlated stellar accretion rates within the Lupus star-forming region argue in favour of an environmental influence on stellar accretion, possibly combined with internal processes in the inner disc. Refined age measurements and searches for evidence of infalling material are potential ways to further test this finding. [ABSTRACT FROM AUTHOR]

Context. CH3CN (methyl cyanide) is one of the simplest and most abundant interstellar complex organic molecules (iCOMs), and has been detected in young solar analogues, shocked regions, protoplanetary discs, and comets. CH3CN can therefore be considered a key species to explore the chemical connections between the planet-forming disk phase and comets. However, for such comparison to be meaningful, kinetics data for the reactions leading to CH3CN formation and destruction must be updated. Aims. Here we focus on the destruction of methyl cyanide through collisions with He+.. We employed a combined experimental and theoretical methodology to obtain cross sections (CSs) and branching ratios (BRs) as a function of collision energy, from which we calculated reaction rate coefficients k(T) in the temperature range from 10 to 300 K. Methods. We measured CSs and BRs using a guided ion beam setup, and developed a theoretical treatment based on an analytical formulation of the potential energy surfaces (PESs) for the charge exchange process. The method employs a Landau Zener model to obtain reaction probabilities at crossings between the entrance and exit PESs, and an adiabatic centrifugal sudden approximation to calculate CSs and k(T), from subthermal to hyper-thermal regimes. Results. k(T) and experimental BRs differ from those predicted from widely used capture models. In particular, the rate coefficient at 10 K is estimated to be almost one order of magnitude smaller than what is reported in the KIDA database. In addition, the charge exchange is completely dissociative and the most abundant fragments are HCCN+/CCNH+ , HCNH+ and CH2+. Conclusions. Our results, combined with a revised chemical network for the formation of CH3CN, support the hypothesis that methyl cyanide in protoplanetary discs could be mostly the product of gas-phase processes rather than grain chemistry, as currently proposed. These findings are expected to have implications in the comparison of the abundance ratios of N-bearing molecules observed in discs with cometary abundance ratios. [ABSTRACT FROM AUTHOR]

Stars mostly form in cluster environments, where neighbouring stars can have an influence on the evolution of the newly formed protoplanetary discs. Besides gravitational interactions, external photoevaporation can also shape protoplanetary discs. Depending on the strength of external photo-evaporation, discs may be destroyed within 1–2 Myrs, or more gradually, depending on whether the external photo-evaporation field is stronger or weaker, respectively. We used the chemcomp code, which includes a viscous disc evolution model including pebble drift and evaporation to calculate the chemical composition of protoplanetary discs. We extended this code to include external photoevaporation following the FRIED grid. Before external photoevaporation becomes efficient, the disc follows a purely viscous disc evolution, where the C/O ratio in the inner disc initially decreases due to inwardly drifting and evaporating water ice pebbles. Over time, the C/O ratio increases again as water vapour is accreted onto the star and carbon-rich gas gradually migrates inwards. However, once external photo-evaporation commences, the outer disc begins to get dispersed. During this process, the inner disc's chemical evolution still follows the evolution of a purely viscous disc because the majority of the pebbles have already drifted inwards on timescales shorter than 1 Myr. At low viscosity, the inner disc's C/O ratio remains sub-solar until the disc is dispersed through external photoevaporation. At a high viscosity, the inner disc's composition can reach super-solar values in C/O, because the water vapour is accreted onto the star faster and carbon rich gas from the outer disc can move inwards faster as well, as long as the disc can survive a few Myrs. In both cases, there is no visible difference in terms of the chemical composition of the inner disc compared to a purely viscous model, due to the rapid inward drift of pebbles that sets the chemical composition of the disc. Thus, our model predicts that the inner disc chemistry would be similar between discs that are subject to external photoevaporation and discs that are isolated and experience no external photo-evaporation. This finding is in line with observations of protoplanetary discs with JWST. [ABSTRACT FROM AUTHOR]

Context. The inner disk of the young star PDS 70 may be a site of rocky planet formation, with two giant planets detected further out. Recently, James Webb Space Telescope/Mid-Infrared Instrument (JWST/MIRI) Medium-Resolution Spectrometer (MRS) observations have revealed the presence of warm water vapour in the inner disk. Solids in the inner disk may inform us about the origin of this inner disk water and nature of the dust in the rocky planet-forming regions of the disk. Aims. We aim to constrain the chemical composition, lattice structure, and grain sizes of small silicate grains in the inner disk of PDS 70, observed both in JWST/MIRI MRS and the Spitzer Infrared Spectrograph (Spitzer IRS). Methods. We used a dust fitting model, called DuCK, based on a two-layer disk model considering three different sets of dust opacities. We used Gaussian random field and distribution of hollow spheres models to obtain two sets of dust opacities using the optical constants of cosmic dust analogs derived from laboratory-based measurements. These sets take into account the grain sizes as well as their shapes. The third set of opacities was obtained from the experimentally measured transmission spectra from aerosol spectroscopy. We used stoichiometric amorphous silicates, forsterite, and enstatite in our analysis. We also studied the iron content of crystalline olivine using the resonance at 23–24 μm and tested the presence of fayalite. Both iron-rich and magnesium-rich amorphous silicate dust species were also employed to fit the observed spectra. Results. The Gaussian random field opacity set agrees well with the observed spectrum, better than the other two opacity sets. In both MIRI and Spitzer spectra, amorphous silicates are the dominant dust species. Crystalline silicates are dominated by iron-poor olivine. The 23–24 μm olivine band peaks at 23.44 μm for the MIRI spectrum and 23.47 μm for the Spitzer spectrum, representing around or less than 10% of iron content in the crystalline silicate. In all of the models, we do not find strong evidence for enstatite. Moreover, the silicate band in the MIRI spectrum indicates larger grain sizes (a few microns up to 5 μm) than the Spitzer spectrum (0.1–1 μm), indicating a time-variable small grain reservoir. Conclusions. The inner PDS 70 disk is dominated by a variable reservoir of warm (T~350–500 K) amorphous silicates, with ~15% of forsterite in mass fraction. The 10μm and 18μm amorphous silicate bands are very prominent, indicating that most emission originates from optically thin dust. We suggest that the small grains detected in the PDS 70 inner disk are likely transported inward from the outer disk as a result of filtration by the pressure bump associated with the gap and fragmentation into smaller sizes at the ice line. Collisions among larger parent bodies may also contribute to the small grain reservoir in the inner disk, but these parent bodies must be enstatite-poor. In addition, the variation between MIRI and Spitzer spectra can be explained by a combination of grain growth over 15 years and a dynamical inner disk where opacity changes occur resulting from the highly variable hot (T~1000 K) innermost dust reservoir. [ABSTRACT FROM AUTHOR]

Context. Protoplanetary disks surrounding young stars are the birth places of planets. Among them, transition disks with inner dust cavities of tens of au are sometimes suggested to host massive companions. Yet, such companions are often not detected. Aims. Some transition disks exhibit a large amount of gas inside the dust cavity and relatively high stellar accretion rates, which contradicts typical models of gas-giant-hosting systems. Therefore, we investigate whether a sequence of low-mass planets can create the appearance of cavities in the dust disk. Methods. We evolve the disks with low-mass growing embryos in combination with 1D dust transport and 3D pebble accretion, to investigate the reduction of the pebble flux at the embryos' orbits. We vary the planet and disk properties to understand the resulting dust profile. Results. We find that multiple pebble-accreting planets can efficiently decrease the dust surface density, resulting in dust cavities consistent with transition disks. The number of low-mass planets necessary to sweep up all pebbles decreases with decreasing turbulent strength and is preferred when the dust Stokes number is 10−2 − 10−4. Compared to dust rings caused by pressure bumps, those by efficient pebble accretion exhibit more extended outer edges. We also highlight the observational reflections: the transition disks with rings featuring extended outer edges tend to have a large gas content in the dust cavities and rather high stellar accretion rates. Conclusions. We propose that planet-hosting transition disks consist of two groups. In Group A disks, planets have evolved into gas giants, opening deep gaps in the gas disk. Pebbles concentrate in pressure maxima, forming dust rings. In Group B, multiple Neptunes (unable to open deep gas gaps) accrete incoming pebbles, causing the appearance of inner dust cavities and distinct ring-like structures near planet orbits. The morphological discrepancy of these rings may aid in distinguishing between the two groups using high-resolution ALMA observations. [ABSTRACT FROM AUTHOR]

Context. The formation and evolution of protoplanetary disks remains elusive. We have numerous astronomical observations of young stellar objects of different ages with their envelopes and/or disks. Moreover, in the last decade, there has been tremendous progress in numerical simulations of star and disk formation. New simulations use realistic equations of state for the gas and treat the interaction of matter and the magnetic field with the full set of nonideal magnetohydrodynamic (MHD) equations. However, it is still not fully clear how a disk forms and whether it happens from inside-out or outside-in. Open questions remain regarding where material is accreted onto the disk and comes from, how dust evolves in disks, and the timescales of appearance of disk's structures. These unknowns limit our understanding of how planetesimals and planets form and evolve. Aims. We attempted to reconstruct the evolutionary history of the protosolar disk, guided by the large amount of cosmochemical constraints derived from the study of meteorites, while using astronomical observations and numerical simulations as a guide to pinpointing plausible scenarios. Methods. Our approach is highly interdisciplinary and we do not present new observations or simulations in this work. Instead, we combine, in an original manner, a large number of published results concerning young stellar objects observations, and numerical simulations, along with the chemical, isotopic and petrological nature of meteorites. Results. We have achieved a plausible and coherent view of the evolution of the protosolar disk that is consistent with cosmochemical constraints and compatible with observations of other protoplanetary disks and sophisticated numerical simulations. The evidence that high-temperature condensates, namely, calcium-aluminum inclusions (CAIs) and amoeboid olivine aggregates (AOAs), formed near the protosun before being transported to the outer disk can be explained in two ways: there could have either been an early phase of vigorous radial spreading of the disk that occurred or fast transport of these condensates from the vicinity of the protosun toward large disk radii via the protostellar outflow. The assumption that the material accreted toward the end of the infall phase was isotopically distinct allows us to explain the observed dichotomy in nucleosynthetic isotopic anomalies of meteorites. It leads us toward intriguing predictions on the possible isotopic composition of refractory elements in comets. At a later time, when the infall of material waned, the disk started to evolve as an accretion disk. Initially, dust drifted inward, shrinking the radius of the dust component to ∼45 au, probably about to about half of the width of the gas component. Next, structures must have emerged, producing a series of pressure maxima in the disk, which trapped the dust on Myr timescales. This allowed planetesimals to form at radically distinct times without significantly changing any of the isotopic properties. We also conclude that there was no late accretion of material onto the disk via streamers. The disk disappeared at about 5 My, as indicated by paleomagnetic data in meteorites. Conclusions. The evolution of the protosolar disk seems to have been quite typical in terms of size, lifetime, and dust behavior. This suggests that the peculiarities of the Solar System with respect to extrasolar planetary systems probably originate from the chaotic nature of planet formation and not from the properties of the parental disk itself. [ABSTRACT FROM AUTHOR]

The disk instability model is a promising pathway for giant planet formation in various conditions. At the moment, population synthesis models are used to investigate the outcomes of this theory, where a key ingredient of the disk population evolution are collisions of self-gravitating clumps formed by the disk instabilities. In this study, we explored the wide range of dynamics between the colliding clumps by performing state-of-the-art smoothed particle hydrodynamics simulations with a hydrogen-helium mixture equation of state and investigated the parameter space of collisions between clumps of different ages, masses (1–10 Jupiter mass), various impact conditions (head-on to oblique collisions) and a range of relative velocities. We find that the perfect merger assumption used in population synthesis models is rarely satisfied and that the outcomes of most of the collisions lead to erosion, disruption or a hit-and-run. We also show that in some cases collisions can initiate the dynamical collapse of the clump. We conclude that population synthesis models should abandon the simplifying assumption of perfect merging. Relaxing this assumption will significantly affect the inferred population of planets resulting from the disk instability model. [ABSTRACT FROM AUTHOR]

Context. Stars and planets form in regions of enhanced stellar density, subjecting protoplanetary discs to gravitational perturbations from neighbouring stars. Observations in the Taurus star-forming region have uncovered evidence of at least three recent, star-disc encounters that have truncated discs (HV/DO Tau, RW Aurigae, and UX Tau), raising questions about the frequency of such events. Aims. We aim to assess the probability of observing truncating star-disc encounters in Taurus. Methods. We generated a physically motivated dynamical model including binaries and a spatial-kinematic substructure to follow the historical dynamical evolution of the Taurus star-forming region. We used this model to track star-disc encounters and the resulting outer disc truncation over the lifetime of Taurus. Results. A quarter of discs are truncated below 30 au by dynamical encounters, but this truncation mostly occurs in binaries over the course of a few orbital periods, on a timescale ≲0.1 Myr. Nonetheless, some truncating encounters still occur up to the present age of Taurus. Strongly truncating encounters (ejecting ≳10 percent of the disc mass) occur at a rate ∼10 Myr−1, sufficient to explain the encounter between HV and DO Tau ∼0.1 Myr ago. If encounters that eject only ∼1 percent of the disc mass are responsible for RW Aurigae and UX Tau, then they are also expected with encounter rate Γenc ∼ 100–200 Myr−1. However, the observed sample of recent encounters is probably incomplete, since these examples occurred in systems that are not consistent with a random drawing from the mass function. One more observed example would statistically imply additional physics, such as replenishment of the outer disc material. Conclusions. The marginal consistency of the frequency of observed recent star-disc encounters with theoretical expectations underlines the value of future large surveys searching for external structures associated with recent encounters. The outcome of such a survey offers a highly constraining, novel probe of protoplanetary disc physics. [ABSTRACT FROM AUTHOR]

The streaming instability is a mechanism whereby pebble-sized particles in protoplanetary discs spontaneously come together in dense filaments, which collapse gravitationally to form planetesimals upon reaching the Roche density. The extent of the filaments along the orbital direction is nevertheless poorly characterised, due to a focus in the literature on small simulation domains where the behaviour of the streaming instability on large scales cannot be determined. We present here computer simulations of the streaming instability in boxes with side lengths up to 6.4 scale heights in the plane. This is 32 times larger than typically considered simulation domains and nearly a factor 1000 times the volume. We show that the azimuthal extent of filaments in the non-linear state of the streaming instability is limited to approximately one gas scale height. The streaming instability will therefore not transform the pebble density field into axisymmetric rings; rather the non-linear state of the streaming instability appears as a complex structure of loosely connected filaments. Including the self-gravity of the pebbles, our simulations form up to 4000 planetesimals. This allows us to probe the high-mass end of the initial mass function of planetesimals with much higher statistical confidence than previously. We find that this end is well-described by a steep exponential tapering. Since the resolution of our simulations is moderate – a necessary trade-off given the large domains – the mass distribution is incomplete at the low-mass end. When putting comparatively less weight on the numbers at low masses, at intermediate masses we nevertheless reproduce the power-law shape of the distribution established in previous studies. [ABSTRACT FROM AUTHOR]

In protoplanetary discs, small millimetre-centimetre-sized pebbles drift inwards which can aid in planetary growth and influence the chemical composition of their natal discs. Gaps in protoplanetary discs can hinder the effective inward transport of pebbles by trapping the material in pressure bumps. In this work, we explore how multiple planets change the vapour enrichment by gap opening. For this, we extended the chemcomp code to include multiple growing planets and investigated the effect of 1, 2, and 3 planets on the water content and C/O ratio in the gas disc as well as the final composition of the planetary atmosphere. We followed planet migration over evaporation fronts and found that previously trapped pebbles evaporate relatively quickly and enrich the gas. We also found that in a multi-planet system, the atmosphere composition can be reduced in carbon and oxygen compared to the case without other planets, due to the blocking of volatile-rich pebbles by an outer planet. This effect is stronger for lower viscosities because planets migrate further at higher viscosities and eventually cross inner evaporation fronts, releasing previously trapped pebbles. Interestingly, we found that nitrogen remains super-stellar regardless of the number of planets in the system such that super-stellar values in N/H of giant planet atmospheres may be a tracer for the importance of pebble drift and evaporation. [ABSTRACT FROM AUTHOR]