Search

Using long-slit and panoramic spectroscopy at the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences and by mapping emission lines in a narrow passband of 13 Å with the MaNGaL instrument at the 2.5-m telescope of the Caucasus Mountain Observatory of the Sternberg Astronomical Institute of the Lomonosov Moscow State University, we have investigated the gaseous component of the giant lenticular galaxy NGC 934. The gas kinematics in the galaxy has turned out to disagree completely with the stellar kinematics, suggesting recent accretion of a large amount of cold gas by the galaxy. Weak star formation proceeds in the accreted gas on the periphery of the galaxy, mainly in a ring of radius 26 kpc, which may promise the buildup of a giant low-surface-brightness stellar disk in this early-type galaxy. The gas metallicity in the star formation ring is nearly solar: the accretion source is most likely the swallowing of a massive gas-rich satellite. [ABSTRACT FROM AUTHOR]

With high-resolution spectroscopy, we can study exoplanet atmospheres and learn about their chemical composition, temperature profiles, and presence of clouds and winds, mainly in hot, giant planets. State-of-the-art instrumentation is pushing these studies towards smaller exoplanets. Of special interest are the few planets in the 'Neptune desert', a lack of Neptune-sized planets in close orbits around their hosts. Here, we assess the presence of water in one such planet, the bloated super-Neptune WASP-166 b, which orbits an F9-type star in a short orbit of 5.4 d. Despite its close-in orbit, WASP-166 b preserved its atmosphere, making it a benchmark target for exoplanet atmosphere studies in the desert. We analyse two transits observed in the visible with ESPRESSO. We clean the spectra from the Earth's telluric absorption via principal component analysis, which is crucial to the search for water in exoplanets. We use a cross-correlation-to-likelihood mapping to simultaneously estimate limits on the abundance of water and the altitude of a cloud layer, which points towards a low water abundance and/or high clouds. We tentatively detect a water signal blue-shifted ∼5 |$\mathrm{km\, s^{-1}}$| from the planetary rest frame. Injection and retrieval of model spectra show that a solar-composition, cloud-free atmosphere would be detected at high significance. This is only possible in the visible due to the capabilities of ESPRESSO and the collecting power of the VLT. This work provides further insight on the Neptune desert planet WASP-166 b, which will be observed with JWST. [ABSTRACT FROM AUTHOR]

Various interactions affect the population of close-in planets. Among them, the tidal and magnetic interactions drive orbital decay and star-planet angular momentum exchange, leading to stellar spin-up. As a result of the above processes, a planet may initiate the mass transfer to the host star once it encounters the Roche limit. Another mechanism providing substantial mass-loss is associated with the atmospheric escape caused by photoevaporation followed by orbital expansion, which is thought to be important for hot Neptunes and super-Earths. Thus, the fraction of the initial number of hot Jupiters may transform into lower-mass planets through the Roche lobe overflow (RLO) phase and continue secular evolution under the effect of photoevaporation. In this paper, we compile the latest prescriptions for tidal and magnetic migration and mass-loss rates to explore the dynamics of hot Jupiter systems. We study how the implemented interactions shape the orbital architecture of Jovian planets and whether their impact is enough to reproduce the observational sample. Our models suggest that the tidal interaction is able to generate the upper boundary of the hot Jupiter population in the mass–separation diagram. To recreate the sub-Jovian desert, we need to make additional assumptions regarding the RLO phase or the influence of the protoplanetary disc's inner edge on the initial planetary location. According to our estimates, 12–15 per cent of hot Jupiters around solar-mass stars have been engulfed or become lower-mass planets. 0.20–0.25 per cent of the present-day giant planet population undergoes decay intense enough to be detected with modern facilities. [ABSTRACT FROM AUTHOR]

We present a Zeeman–Doppler imaging study of two weak-line T Tauri stars TAP 4 and TAP 40, based on the high-resolution spectropolarimetric observations with ESPaDOnS at the Canada–France–Hawaii Telescope in November 2013, in the framework of the Magnetic Topologies of Young Stars and Survival of close-in giant Exoplanets large programme. We apply two Zeeman–Doppler imaging codes to the Stokes I and V profiles to reconstruct their brightness and large-scale magnetic field images. The results given by the two imaging codes are in good agreement with each other. TAP 4 shows a large polar cool spot and several intermediate-latitude warm spots on its surface, whereas TAP 40 exhibits very weak variations in its Stokes I profiles, suggesting a mostly unspotted photosphere. We detect Zeeman signatures in the Stokes V profiles of both stars. The reconstructed magnetic maps reveal dominantly toroidal fields, which enclose about 60 per cent of the total magnetic energy for both TAP 4 and TAP 40. Both stars show prominent circular ring features of the azimuthal magnetic field. We derive a solar-like surface differential rotation on TAP 4 from the tomographic modelling. The brightness image of TAP 4 is used to predict the radial velocity (RV) jitters induced by its activity. After filtering out the activity jitter, the rms of its RVs is reduced from 1.7 to 0.2 km s−1, but we do not detect any periodic signals in the filtered RVs of TAP 4, implying that it is unlikely to host a close-in exoplanet more massive than ∼3.5 M Jup at 0.1 au. [ABSTRACT FROM AUTHOR]

The atmospheric C/O ratio of exoplanets is widely used to constrain their formation. To guarantee that the C/O ratio provides robust information, we need to accurately quantify the amount of C and O in exoplanetary atmospheres. In the case of O, water and carbon monoxide are generally studied as the two key carriers. However, oxygen is a very reactive element and does not bind only with carbon; depending on the temperature, it also binds to refractory elements. Estimating the amount of oxygen bound to refractory elements is therefore critical for unbiased estimates of the C/O ratio. In this work, we investigate the oxygen deficit due to refractory elements and its effects on the atmospheric C/O ratio of giant exoplanets as a function of their metallicity and equilibrium temperature. We model the composition of planetary atmospheres assuming chemical equilibrium and using as input physically justified elemental mixtures arising from detailed planet formation simulations. Our results show how the interplay between the atmospheric temperature and non-solar abundances of oxygen and refractory elements can sequester large fractions of oxygen, introducing significant biases in evaluating the C/O ratio when this effect is not accounted for. We apply our results to the case of Jupiter in the Solar system and show how the currently estimated water abundance points to a true oxygen abundance that is four times the solar one. [ABSTRACT FROM AUTHOR]

Debris discs consist of belts of bodies ranging in size from dust grains to planetesimals; these belts are visible markers of planetary systems around other stars that can reveal the influence of extrasolar planets through their shape and structure. Two key stirring mechanisms – self-stirring by planetesimals and secular perturbation by an external giant planet – have been identified to explain the dynamics of planetesimal belts; their relative importance has been studied independently, but are yet to be considered in combination. In this work, we perform a suite of 286  N -body simulations exploring the evolution of debris discs over 1 Gyr, combining the gravitational perturbations of both dwarf planets embedded in the discs, and an interior giant planet. Our systems were somewhat modelled after the architecture of the outer Solar system: a Solar mass star, a single massive giant planet at 30 au (M GP = 10 to 316 M⊕), and a debris disc formed by 100 massive dwarf planets and 1000 massless particles (M DD = 3.16 to 31.6 M⊕). We present the evolution of both the disc and the giant planet after 1 Gyr. The time evolution of the average eccentricity and inclination of the disc is strongly dependent on the giant planet mass as well as on the remaining disc mass. We also found that efficient stirring is achieved even with small disc masses. In general, we find that a mixed mechanism is more efficient in the stirring of cold debris discs than either mechanism acting in isolation. [ABSTRACT FROM AUTHOR]

Direct imaging of gas giant exoplanets provides information on their atmospheres and the architectures of planetary systems. However, few planets have been detected in blind surveys with direct imaging. Using astrometry from the Gaia and Hipparcos spacecraft, we identified dynamical evidence for a gas giant planet around the nearby star HIP 99770. We confirmed the detection of this planet with direct imaging using the Subaru Coronagraphic Extreme Adaptive Optics instrument. The planet, HIP 99770 b, orbits 17 astronomical units from its host star, receiving an amount of light similar to that reaching Jupiter. Its dynamical mass is 13.9 to 16.1 Jupiter masses. The planet-to-star mass ratio [(7 to 8) × 10−3] is similar to that of other directly imaged planets. The planetÕs atmospheric spectrum indicates an older, less cloudy analog of the previously imaged exoplanets around HR 8799. [ABSTRACT FROM AUTHOR]

The class of transiting cold Jupiters, orbiting at ≳0.5–1.0 au, is to-date underpopulated. Probing their atmospheric composition and physical characteristics is particularly valuable, as it allows for direct comparisons with the Solar system giant planets. We investigate some aspects of the synergy between Gaia astrometry and other ground-based and space-borne programs for detection and characterization of such companions. We carry out numerical simulations of Gaia observations of systems with one cold transiting gas giant, using Jovian planets around a sample of nearby low-mass stars as proxies. Using state-of-the-art orbit fitting tools, we gauge the potential of Gaia astrometry to predict the time of transit centre T c for the purpose of follow-up observations to verify that the companions are indeed transiting. Typical uncertainties on T c will be on the order of a few months, reduced to several weeks for high astrometric signal-to-noise ratios and periods shorter than ∼3 yr. We develop a framework for the combined analysis of Gaia astrometry and radial-velocity data from representative ground-based campaigns and show that combined orbital fits would allow to significantly reduce the transit windows to be searched for, down to about ±2 weeks (2–σ level) in the most favourable cases. These results are achievable with a moderate investment of observing time (∼0.5 nights per candidate, ∼50 nights for the top 100 candidates), reinforcing the notion that Gaia astrometric detections of potentially transiting cold giant planets, starting with Data Release 4, will constitute a valuable sample worthy of synergistic follow-up efforts with a variety of techniques. [ABSTRACT FROM AUTHOR]

Hydrogen and helium are the most abundant elements in the universe, and they constitute the interiors of gas giant planets. Thus, their equations of states, phase, chemical state, and chemical reactivity at extreme conditions are of great interest. Applying Raman spectroscopy, visual observation, and synchrotron X-ray diffraction in diamond anvil cells, we performed experiments on H2–He 1:1 and D2–He 1:10 compressed gas mixtures up to 100 GPa at 300 K. By comparing with the available data on pure bulk materials, we find no sign of miscibility, chemical reactivity, and new compound formation. This result establishes a new baseline for future investigations of miscibility in the He–H2 system at extreme P-T conditions. [ABSTRACT FROM AUTHOR]

Context. When considering the migration of Jupiter and Saturn, a classical result is to find the planets migrating outwards and locked in the 3:2 mean motion resonance (MMR). These results were obtained in the framework of viscously accreting discs, in which the observed stellar accretion rates constrained the viscosity values. However, it has recently been shown observationally and theoretically that discs are probably less viscous than previously thought. Aims. Therefore, in this paper, we explore the dynamics of pairs of giant planets in low-viscosity discs. Methods. We performed two-dimensional hydrodynamical simulations using the grid-based code FARGOCA. Results. In contrast to classical viscous discs, we find that the outer planet never crosses the 2:1 resonance and the pair does not migrate outwards. After a wide parameter exploration, including the mass of the outer planet, we find that the planets are primarily locked in the 2:1 MMR and in some cases in the 5:2 MMR. We explain semi-analytically why it is not possible for the outer planet to cross the 2:1 MMR in a low-viscosity disc. Conclusions. We find that pairs of giant planets migrate inwards in low-viscosity discs. Although, in some cases, having a pair of giant planets can slow down the migration speed with respect to a single planet. Such pairs of slowly migrating planets may be located, at the end of the disc phase, in the population of exoplanets of 'warm Jupiters'. However, the planets never migrate outwards. These results could have strong implications on the Solar System's formation scenarios if the Sun's protoplanetary disc had a low viscosity. [ABSTRACT FROM AUTHOR]

Context. Measurements of the occultation of an exoplanet at visible wavelengths allow us to determine the reflective properties of a planetary atmosphere. The observed occultation depth can be translated into a geometric albedo. This in turn aids in characterising the structure and composition of an atmosphere by providing additional information on the wavelength-dependent reflective qualities of the aerosols in the atmosphere. Aims. Our aim is to provide a precise measurement of the geometric albedo of the gas giant HD189733b by measuring the occultation depth in the broad optical bandpass of CHEOPS (350-1100 nm). Methods. We analysed 13 observations of the occultation of HD189733b performed by CHEOPS utilising the Python package PyCHEOPS. The resulting occultation depth is then used to infer the geometric albedo accounting for the contribution of thermal emission from the planet. We also aid the analysis by refining the transit parameters combining observations made by the TESS and CHEOPS space telescopes. Results. We report the detection of an 24:7 ± 4:5 ppm occultation in the CHEOPS observations. This occultation depth corresponds to a geometric albedo of 0:076 ± 0:016. Our measurement is consistent with models assuming the atmosphere of the planet to be cloud-free at the scattering level and absorption in the CHEOPS band to be dominated by the resonant Na doublet. Taking into account previous optical-light occultation observations obtained with the Hubble Space Telescope, both measurements combined are consistent with a super-stellar Na elemental abundance in the dayside atmosphere of HD189733b. We further constrain the planetary Bond albedo to between 0.013 and 0.42 at 3 confidence. Conclusions. We find that the reflective properties of the HD189733b dayside atmosphere are consistent with a cloud-free atmosphere having a super-stellar metal content. When compared to an analogous CHEOPS measurement for HD209458b, our data hint at a slightly lower geometric albedo for HD189733b (0:076 ± 0:016) than for HD209458b (0:096 ± 0:016), or a higher atmospheric Na content in the same modelling framework. While our constraint on the Bond albedo is consistent with previously published values, we note that the higher-end values of ~0.4, as derived previously from infrared phase curves, would also require peculiarly high reflectance in the infrared, which again would make it more difficult to disentangle reflected and emitted light in the total observed flux, and therefore to correctly account for reflected light in the interpretation of those phase curves. Lower reported values for the Bond albedos are less affected by this ambiguity. [ABSTRACT FROM AUTHOR]

Context. The equation of state for hydrogen and helium is fundamental for studying stars and giant planets. It has been shown that because of interactions at atomic and molecular levels, the behaviour of a mixture of hydrogen and helium cannot be accurately represented by considering these elements separately. Aims. This paper aims at providing a simple method to account for interactions between hydrogen and helium in interior and evolution models of giant planets. Methods. Using on the one hand ab initio simulations that involve a system of interacting hydrogen and helium particles and pure equations of state for hydrogen and helium on the other, we derived the contributions in density and entropy of the interactions between hydrogen and helium particles. Results. We show that relative variations of up to 15% in density and entropy arise when non-ideal mixing is accounted for. These non-ideal mixing effects must be considered in interior models of giant planets based on accurate gravity field measurements, particularly in the context of variations in the helium-to-hydrogen ratio. They also affect the mass-radius relation of exoplanets. We provide a table that contains the volume and entropy of mixing as a function of pressure and temperature. This table is to be combined with pure hydrogen and pure helium equations of state to obtain an equation of state that self-consistently includes mixing effects for any hydrogen and helium mixing ratio and may be used to model the interior structure and evolution of giant planets to brown dwarfs. Conclusions. Non-linear mixing must be included in accurate calculations of the equations of state of hydrogen and helium. Uncertainties on the equation of state still exist, however. Ab initio calculations of the behaviour of the hydrogen-helium mixture in the megabar regime for various compositions should be performed in order to gain accuracy. [ABSTRACT FROM AUTHOR]

Observations of dust in protoplanetary disks with the Atacama Large Millimeter Array (ALMA) are revealing the existence of substructures such as rings, gaps, and cavities. This morphology is expected to be the outcome of dynamical interaction between the disks and (embedded) planets. However, other mechanisms are able to produce similar dust substructures. A solution to discriminate the gap formation mechanism is to look at the perturbation induced by the planet on the gas surface density and/or the kinematics. In the case of the disk around AS 209, a prominent gap has been reported in the surface density of CO at r ~ 100 au. A further gas gap was identified at r ~ 200 au. Recently, a localized velocity perturbation was reported in the 12CO J = 2-1 emission along with a clump in 13CO J = 2-1 at nearly 200 au and this was interpreted as a gaseous circumplanetary disk. In this paper, we report a new analysis of ALMA archival observations of 12CO and 13CO J = 2-1 in AS 209. We detected a clear kinematics perturbation (kink) in multiple channels and over a wide azimuth range in both datasets. We compared the observed perturbation with a semianalytic model of velocity perturbations due to planet-disk interaction. Based on our analysis, the observed kink is not consistent with a planet at 200 au, as this would require a low gas-disk scale height (<0.05) in contradiction with the previous estimate (h/r ~ 0.118 at r = 100 au). When we fix the disk scale height to 0.118 (at r = 100 au), we find instead that a planet at 100 au induces a kinematics perturbation similar to the one observed. The kink amplitude in the various channels implies a planet mass of 3-5 MJup. Thus, we conclude that a giant protoplanet orbiting at r ~ 100 au is responsible for the large-scale kink as well as for the perturbed dust and gas surface density previously detected. The position angle of the planet is constrained to be between 60 and 100 (east of north). The 200 au gap visible in the 12CO J = 2-1 moment zero map is likely due to density fluctuations induced by the spiral wake. Future observations using the high-contrast imaging technique in the near- and mid-infrared (e.g., with JWST and/or VLT/ERIS) are needed to confirm the presence and position of such a planet. [ABSTRACT FROM AUTHOR]

Context. Most studies devoted to Herbig Ae/Be stars (HAeBes) assume solar metallicity. However, the stellar metallicity, [M/H], is a fundamental parameter that can strongly differ depending on the source and may have important implications for planet formation. It has been proposed that the deficit of refractory elements observed in the surfaces of some HAeBes may be linked to the presence of cavities in their disks and is likely caused by Jovian planets that trap the metal-rich content. Aims. This work aims to provide a robust test on the previous proposal by analyzing the largest sample of HAeBes characterized by homogeneously derived [M/H] values and stellar and circumstellar properties. Methods. The spectra of 67 HAeBes, along with their well-known properties drawn from our previous work, have been collected from the ESO Science Archive Facility. Their [M/H] values were derived based on the comparison with Kurucz synthetic models. Statistical analyses were carried out with the aim to test the potential relation between [M/H] and the Meeus group I sources, with spectral energy distributions (SEDs) associated with the presence of cavities potentially carved by giant planets. We critically analyzed the eventual link between [M/H], the SED groups, and the presence of such planets. Results. Our statistical study robustly confirms that group I sources tend to have a lower [M/H] (typically ~ −0.10) than that of group II HAeBes (~ +0.14). A similar analysis involving SED-based transitional disks, with infrared excess only at wavelengths of ≥2.2 µm, does not reveal such a relation with [M/H]. This result indicates that not all processes capable of creating holes in the inner dust disks end up having an effect on the stellar abundances. The spatial distributions of group I and II sources are similar, at least within the available range of distances to the galactic centre and the galactic plane, for which the observed [M/H] differences are not driven by environmental effects. In addition, group I sources tend to have stronger (sub-) mm continuum emission presumably related to the presence of giant planets. Indeed, literature results indicate that disk substructures probably associated with the presence of giant planets are up to ten times more frequent in group I HAeBes than in group II. Finally, along with the metallicities derived for the whole sample, surface gravities and projected rotational velocities are additional outcomes reported in this work. Conclusions. We provide indirect evidence to suggest that giant planets are more frequent around group I/low [M/H] stars than around the rest of the HAeBes. However, a direct test of the previous hypothesis requires multiple detections of forming planets in their disks. Such detections have so far been limited to the candidate around the metal depleted ([M/H] = −0.35 ± −0.25) group I HAeBe star AB Aur, which is consistent with our findings. [ABSTRACT FROM AUTHOR]

Context. Young giant planets are the best targets for characterization with direct imaging. The Medium Resolution Spectrometer (MRS) of the Mid-Infrared Instrument (MIRI) of the recently launched James Webb Space Telescope (JWST) will give access to the first spectroscopic data for direct imaging above 5 µm with unprecedented sensitivity at a spectral resolution of up to 3700. This will provide a valuable complement to near-infrared data from ground-based instruments for characterizing these objects. Aims. We aim to evaluate the performance of MIRI/MRS in detecting molecules in the atmosphere of exoplanets and in constraining atmospheric parameters using Exo-REM atmospheric models. Methods. The molecular mapping technique based on cross-correlation with synthetic models was recently introduced. We test this promising detection and characterization method on simulated MIRI/MRS data. Results. Directly imaged planets can be detected with MIRI/MRS, and we are able to detect molecules (H2O, CO, NH3, CH4, HCN, PH3, CO2) at various angular separations depending on the strength of the molecular features and brightness of the target. We find that the stellar spectral type has a weak impact on the detection level. This method is globally most efficient for planets with temperatures below 1500 K, for bright targets, and for angular separations of greater than 1′′. Our parametric study allows us to anticipate the ability to characterize planets that will be detected in the future. Conclusions. The MIRI/MRS will give access to molecular species not yet detected in exoplanetary atmospheres. The detection of molecules acting as indicators of the temperature of the planets will make it possible to discriminate between various hypotheses of the preceding studies, and the derived molecular abundance ratios should bring new constraints on planet-formation scenarios. [ABSTRACT FROM AUTHOR]

Context. NOTT (formerly Hi-5) is a new high-contrast L′ band (3.5–4.0 µm) beam combiner for the VLTI designed with an ambitious aim to be sensitive to young giant exoplanets down to 5 mas separation around nearby stars. The performance of nulling interferometers in these wavelengths is affected both by fundamental noise from the background and contributions of instrumental noise. This motivates the development of end-to-end simulations to optimize these instruments. Aims. The aim of this study is to enable a performance evaluation of NOTT and inform the design of such instruments with current and future infrastructures in mind, taking into account the different sources of noise and their correlation. Methods. SCIFYsim is an end-to-end simulator for single-mode-filtered beam combiners, with an emphasis on nulling interferometers. We use it to compute a covariance matrix of the errors. We then use statistical detection tests based on likelihood ratios to compute compound detection limits for the instrument. Results. With the current assumptions as to the performance of the wavefront correction systems, the errors are dominated by correlated instrumental errors down to stars of magnitude 6–7 in the L band, beyond which thermal background from the telescopes and relay system becomes dominant. Conclusions. SCIFYsim is suited to anticipating some of the challenges of design, tuning, operation, and signal processing for integrated-optics beam combiners. The detection limits found for this early version of NOTT simulation with the unit telescopes are compatible with detections at contrasts up to 105 in the L band at separations of 5–80 mas around bright stars. [ABSTRACT FROM AUTHOR]

We report the first simulations of planetary system dynamics as affected by an embedded cluster environment. Such environments are generally believed to be relevant for the large majority of newborn stars of solar type. Moreover, our cluster model is more realistic than in previous work. We focus on a giant planet system with five members, which represents a likely precursor of our solar system. Our main result is that the perturbing effects of close encounters with cluster stars trigger dynamical chaos leading to breakdown of the system with a significant probability, especially if the natal gas discs are short-lived and the clusters are highly concentrated. When breakdown occurs, all planets except Jupiter suffer a large risk of being ejected from the system or extracted into distant orbits with semimajor axes of hundreds or thousands of astronomical units. This is consistent with recent estimates of a large abundance of low-mass, free-floating planets. We demonstrate a possibility for Jupiter and Saturn to evolve into hot Jupiter orbits by tidal circularization during the chaotic evolution. Even so, the low occurrence rate of this outcome indicates that the real hot Jupiters in general have an origin unrelated to dynamical evolution in birth clusters. [ABSTRACT FROM AUTHOR]

Giant planets embedded in protoplanetary disks (PPDs) can create annulus density gaps around their orbits in the type-II regime, potentially responsible for the ubiquity of annular substructures observed in PPDs. Although a substantial amount of works studying type-II planetary migration and gap properties have been published, they have almost exclusively all been conducted under the viscous accretion disk framework. However, recent studies have established magnetized disk winds as the primary mechanism driving disk accretion and evolution, which can coexist with turbulence from the magnetorotational instability (MRI) in the outer PPDs. We conduct a series of 3D global nonideal magnetohydrodynamic (MHD) simulations of type-II planet–disk interactions applicable to the outer PPDs. Our simulations properly resolve the MRI turbulence and accommodate the MHD disk wind. We found that the planet triggers the poloidal magnetic flux concentration around its orbit. The concentrated magnetic flux strongly enhances angular momentum removal in the gap, which is along the inclined poloidal field through a strong outflow emanating from the disk surface outward to the planet gap. The resulting planet-induced gap shape is more similar to an inviscid disk, while being much deeper, which can be understood from a simple inhomogeneous wind torque prescription. The corotation region is characterized by a fast trans-sonic accretion flow that is asymmetric in azimuth about the planet and lacking the horseshoe turns, and the meridional flow is weakened. The torque acting on the planet generally drives inward migration, though the migration rate can be affected by the presence of neighboring gaps through stochastic, planet-free magnetic flux concentration. [ABSTRACT FROM AUTHOR]

Using self-consistent models of turbulent particle growth in an evolving protoplanetary nebula of solar composition, we find that recently proposed local metallicity and Stokes number criteria necessary for the streaming instability to generate gravitationally bound particle overdensities are generally not approached anywhere in the disk during the first million years, an epoch in which meteoritic and observational evidence strongly suggests that the formation of the first planetesimals and perhaps giant planet core accretion are already occurring. [ABSTRACT FROM AUTHOR]

Many potential mechanisms for delivering planetary debris to within a few Roche radii of white dwarfs rely on gravitational scattering events that feature perturbers which are giant planets or terrestrial planets. However, the population of these planets orbiting white dwarfs is still unknown, and for a substantial fraction of white dwarfs the largest planetary survivors of stellar evolution may be sub-terrestrial mass minor planets. Here, we attempt to identify the smallest mass perturbers that could pollute white dwarfs. Through computationally expensive numerical simulations of both unstable and stable configurations of minor planets, we find that this critical lower bound equals approximately one Luna mass (1 M ☾ ≈ 10-1 M ♂ ≈ 10-2 M ⊕ ≈ 102 M Ceres). Further, we find that as this mass limit is approached from above, the typical cooling age at which white dwarf pollution occurs increases. Consequently, there is a two order-of-magnitude range of perturber masses between Earth and its moon that has remained largely unexplored in white dwarf pollution studies, despite the potential formation of thousands of such Luna-sized objects in these systems. [ABSTRACT FROM AUTHOR]

Intermediate-mass stars (IMSs) represent the link between low-mass and high-mass stars, and cover a key mass range for giant planet formation. In this paper, we present a spectroscopic survey of 241 young IMS candidates with IR-excess, the most complete unbiased sample to date within 300 pc. We combined VLT/X-Shooter spectra with BVR photometric observations and Gaia DR3 distances to estimate fundamental stellar parameters such as T eff, mass, radius, age, and luminosity. We further selected those stars within the intermediate-mass range 1.5 ≤ M ⋆/M⊙ ≤ 3.5, and discarded old contaminants. We used 2MASS and WISE photometry to study the IR-excesses of the sample, finding 92 previously unidentified stars with IR-excess. We classified this sample into 'protoplanetary', 'hybrid candidates', and 'debris' discs based on their observed fractional excess at 12  |$\mu$| m, finding a new population of 17 hybrid disc candidates. We studied inner disc dispersal time-scales for |$\lambda < 10 \,\mu$| m and found very different trends for IMSs and low-mass stars (LMSs). IMSs show excesses dropping fast during the first 6 Myr independently of the wavelength, while LMSs show consistently lower fractions of excess at the shortest wavelengths, and increasingly higher fractions for longer wavelengths with slower dispersal rates. In conclusion, this study demonstrates empirically that IMSs dissipate their inner discs very differently than LMSs, providing a possible explanation for the lack of short period planets around IMSs. [ABSTRACT FROM AUTHOR]

Radio observations of the atmospheres of the giant planets Jupiter, Saturn, Uranus, and Neptune have provided invaluable constraints on atmospheric dynamics, physics/chemistry, and planet formation theories over the past 70 years. We provide a brief history of these observations, with a focus on recent and state-of-the-art studies. The global circulation patterns, as derived from these data, in combination with observations at UV/visible/near-IR wavelengths and in the thermal infrared, suggest a vertically-stacked pattern of circulation cells in the troposphere, with the top cell similar to the classical picture, overlying cells with the opposite circulation. Data on the planets' bulk compositions are used to support or disfavor different planet formation scenarios. While heavy element enrichment in the planets favors the core accretion model, we discuss how the observed relative enrichments in volatile species constrain models of the outer proto-planetary disk and ice giant accretion. Radio observations of planets will remain invaluable in the next decades, and we close with some comments on the scientific gain promised by proposed and under-construction radio telescopes. [ABSTRACT FROM AUTHOR]

The Transiting Exoplanet Survey Satellite (TESS) mission searches for new exoplanets. The observing strategy of TESS results in high-precision photometry of millions of stars across the sky, allowing for detailed asteroseismic studies of individual systems. In this work, we present a detailed asteroseismic analysis of the giant star HD 76920 hosting a highly eccentric giant planet (e = 0.878) with an orbital period of 415 days, using five sectors of TESS light curve that cover around 140 days of data. Solar-like oscillations in HD 76920 are detected around 52 μ Hz by TESS for the first time. By utilizing asteroseismic modeling that takes classical observational parameters and stellar oscillation frequencies as constraints, we determine improved measurements of the stellar mass (1.22 ± 0.11 M ⊙), radius (8.68 ± 0.34 R ☉), and age (5.2 ± 1.4 Gyr). With the updated parameters of the host star, we update the semimajor axis and mass of the planet as a = 1.165 ± 0.035 au and M p sin i = 3.57 ± 0.22 M Jup . With an orbital pericenter of 0.142 ± 0.005 au, we confirm that the planet is currently far away enough from the star to experience negligible tidal decay until being engulfed in the stellar envelope. We also confirm that this event will occur within about 100 Myr, depending on the stellar model used. [ABSTRACT FROM AUTHOR]

The study of atmospheric electricity of the lower stratosphere and upper troposphere of the ice giant planets can help to understand several physical phenomena such as cloud formation, lightning generation, aerosols growth, or chemical composition. At these depths, galactic radiation is the main energy source able to ionize the atmospheric constituents and to produce a low altitude ionospheric layer that can be similar in magnitude to the upper ionosphere produced by solar radiation and auroral electrons. The presence of aerosols affects the ion‐neutral chemistry by capturing electrons and ions depending on the aerosol size and number density. Here, we present a new one dimensional ionospheric model of Uranus and Neptune able to calculate the number densities of electrons and ions as well as the charging of aerosols between 100 Pa and 4 × 105 Pa. Since the results depends upon the amount and size of the atmospheric aerosols, as well as on the flux of the incoming cosmic radiation, several aerosol models, solar‐cycle conditions, and the effect of the intrinsic magnetic field are considered. Plain Language Summary: Uranus and Neptune form the group of ice giant planets in our solar system. They are mainly composed of hydrogen, helium, and volatiles. These planets are the only ones that have not had a dedicated mission to study their atmospheres in situ. The most valuable information was obtained during the Voyager 2 encounters in 1986 and 1989. Such missions provided a wealth of information and raised important questions that have not been addressed yet. Here, we present a new model to calculate the density of electrical charges in the low‐altitude atmosphere in order to estimate electrical conductivity. We found that a low‐altitude ionosphere is created by cosmic radiation. The presence of aerosols can reduce the amount of electrons by more than three orders of magnitude compared to an aerosol‐free atmosphere. The results of this study can help to understand several important atmospheric processes, such as the formation of aerosols and clouds, as well as the generation of lighting. Key Points: A state model of ions and electrons in the lower ionosphere of Uranus and Neptune has been developedThe size and density distribution of aerosols strongly affect the number density of electrons and ionsThe measurement of the electrical conductivity can be used to study the lower ionospheres of Uranus and Neptune [ABSTRACT FROM AUTHOR]

Planetesimal accretion is a key source for heavy-element enrichment in giant planets. It has been suggested that Jupiter's enriched envelope is a result of planetesimal accretion during its growth, assuming it formed in a massive planetesimal disc. In this study, we simulate Jupiter's formation in this scenario. We assume in situ formation and perform N -body simulations to infer the solid accretion rate. We find that tens-Earth masses of planetesimals can be captured by proto-Jupiter during the rapid gas accretion phase. However, if several embryos are formed near Jupiter's core, which is an expected outcome in the case of a massive planetesimal disc, scattering from the embryos increases the eccentricity and inclination of planetesimals and therefore significantly reduces the accretion efficiency. We also compare our results with published semi-analytical models and show that these models cannot reproduce the N -body simulations especially when the planetesimal disc has a large eccentricity and inclination. We show that when the dynamical evolution of planetesimals is carefully modelled, the total mass of captured planetesimals M cap,tot is 2M⊕ ≲ M cap,tot ≲ 18M⊕. The metallicity of Jupiter's envelope can be explained by the planetesimal accretion in our massive disc model despite the low accretion efficiency coming from the high eccentricity and inclination of planetesimals. Our study demonstrates the importance of detailed modelling of planetesimal accretion during the planetary growth and its implications to the heavy-element mass in gaseous planets. [ABSTRACT FROM AUTHOR]

Transport-induced quenching, i.e. the homogenization of chemical abundances by atmospheric advection, is thought to occur in the atmospheres of hot gas giant exoplanets. While some numerical modelling of this process exists, the three-dimensional nature of transport-induced quenching is underexplored. Here, we present results of 3D cloud- and haze-free simulations of the atmospheres of HAT-P-11b, HD 189733b, HD 209458b, and WASP-17b including coupled hydrodynamics, radiative transfer, and chemistry. Our simulations were performed with two chemical schemes: a chemical kinetics scheme, which is capable of capturing transport-induced quenching, and a simpler, more widely used chemical equilibrium scheme. We find that transport-induced quenching is predicted to occur in atmospheres of all planets in our sample; however, the extent to which it affects their synthetic spectra and phase curves varies from planet to planet. This implies that there is a 'sweet spot' for the observability of signatures of transport-induced quenching, which is controlled by the interplay between the dynamics and chemistry. [ABSTRACT FROM AUTHOR]

We model the early stages of planet formation in the solar system, including continual planetesimal formation, and planetesimal and pebble accretion onto planetary embryos in an evolving disk driven by a disk wind. The aim is to constrain aspects of planet formation that have large uncertainties by matching key characteristics of the solar system. The model produces a good fit to these characteristics for a narrow range of parameter space. Planetary growth beyond the ice line is dominated by pebble accretion. Planetesimal accretion is more important inside the ice line. Pebble accretion inside the ice line is slowed by higher temperatures, partial removal of inflowing pebbles by planetesimal formation and pebble accretion further out in the disk, and increased radial velocities due to gas advection. The terrestrial planets are prevented from accreting much water ice because embryos beyond the ice line reach the pebble-isolation mass before the ice line enters the terrestrial-planet region. When only pebble accretion is considered, embryos typically remain near their initial mass or grow to the pebble-isolation mass. Adding planetesimal accretion allows Mars-sized objects to form inside the ice line, and allows giant-planet cores to form over a wider region beyond the ice line. In the region occupied by Mercury, pebble Stokes numbers are small. This delays the formation of embryos and stunts their growth, so that only low-mass planets can form here. [ABSTRACT FROM AUTHOR]

This study presents observations of two possible substellar survivors of post-main sequence engulfment, currently orbiting white dwarf stars. Infrared and optical spectroscopy of GD 1400 reveals a 9.98 h orbital period, where the benchmark brown dwarf has M 2 = 68 ± 8  M Jup, T eff ≈ 2100 K, and a cooling age under 1 Gyr. A substellar mass in the lower range of allowed values is favoured by the gravitational redshift of the primary. Synthetic brown dwarf spectra are able to reproduce the observed CO bands, but lines below the bandhead are notably overpredicted. The known infrared excess towards PG 0010+281 is consistent with a substellar companion, yet no radial velocity or photometric variability is found despite extensive searches. Three independent stellar mass determinations all suggest enhanced mass-loss associated with binary evolution, where the youngest total age for an isolated star is 7.5 ± 2.5 Gyr. A possible solution to this conundrum is the cannibalization of one or more giant planets, which enhanced mass-loss post-main sequence, but were ultimately destroyed. PG 0010 + 281 is likely orbited by a debris disc that is comfortably exterior to the Roche limit, adding to the growing number of non-canonical discs orbiting white dwarfs. At present, only L-type (brown) dwarfs are known to survive direct engulfment during the post-main sequence, whereas T- and Y-type substellar companions persist at wide separations. These demographics indicate that roughly 50  M Jup is required to robustly avoid post-main sequence annihilation, suggesting all closely orbiting giant planets are consumed, which may contribute to mass-loss and magnetic-field generation in white dwarfs and their immediate progenitors. [ABSTRACT FROM AUTHOR]

The stability of eight nominal fictitious Uranus Trojan orbits over the age of the Solar system has been measured. The initial inclinations, i 0, were 0°, 5°, 15°, and 30° relative to the ecliptic plane. Initial eccentricities ranged from 0 to 0.1 for i 0 = 0° and 5°, and 0 to 0.2 for i 0 = 15° and 30°. Half of the orbits were in the L4 swarm, and half were in the L5 swarm. Orbits in the L4 swarm had mean longitudes 8.8° from the nominal L4 Lagrange point, and orbits in the L5 swarm had mean longitudes 18.2° from the nominal L5 point. I integrated 10 000 massless clones per nominal orbit in the six-body problem (Sun, test particle, and four giant planets) for 4.5 Gyr and calculated the half-life for each orbit. A total of 1291 test particles survived for the entire integration time. Of these survivors, 99 per cent were associated with the nominal orbit with i 0 = 0° in the L4 swarm. These surviving test particles had initial eccentricities in the range e 0 < 0.07. The half-lives associated with L4 orbits were 1258, 286, 56, and 237 Myr for nominal orbits with i 0 = 0°, 5°, 15°, and 30°, respectively. The half-lives associated with L5 orbits were 103, 281, 25, and 46 Myr, respectively. The overall results showed that the ecliptic plane is one good place to search for primordial Uranus Trojans. [ABSTRACT FROM AUTHOR]

The Galactic Centre is known to have undergone a recent star formation episode a few Myr ago, which likely produced many T Tauri stars hosting circumstellar discs. It has been suggested that these discs may be the compact and dusty ionized sources identified as 'G-clouds'. Given the Galactic Centre's hostile environment, we study the possible evolutionary pathways these discs experience. We compute new external photoevaporation models applicable to discs in the Galactic Centre that account for the subsonic launching of the wind and absorption of UV photons by dust. Using evolutionary disc calculations, we find that photoevaporation's rapid truncation of the disc causes them to accrete onto the central star rapidly. Ultimately, an accreting circumstellar disc has a lifetime ≲ 1 Myr, which would fail to live long enough to explain the G-clouds. However, we identify a new evolutionary pathway for circumstellar discs in the Galactic Centre. Removal of disc material by photoevaporation prevents the young star from spinning down due to magnetic braking, ultimately causing the rapidly spinning young star to torque the disc into a 'decretion disc' state which prevents accretion. At the same time, any planetary companion in the disc will trap dust outside its orbit, shutting down photoevaporation. The disc can survive for up to ∼10 Myr in this state. Encounters with other stars are likely to remove the planet on Myr time-scales, causing photoevaporation to restart, giving rise to a G-cloud signature. A giant planet fraction of |$\sim 10{{\ \rm per\ cent}}$| can explain the number of observed G-clouds. [ABSTRACT FROM AUTHOR]

The paper presents original results of comprehensive geochemical studies of samples of oils, condensates, gases, core, and cuttings from wells drilled in the north of Western Siberia. The studies involved chromatographic and mass spectrometric determinations of the molecular and isotopic composition of the oils, gases, condensates, and rock extracts. Analysis of the results, considered together with literature data, made it possible to draw conclusions regarding the source of the hydrocarbons and the mechanism of formation of their accumulations. Information on the molecular and isotopic composition of the fluids and the distribution of their accumulations and fields in the sedimentary cover shows that most of them are of polychronic and polygenic origin. Features of the molecular and isotopic composition of the fluids make it possible to evaluate the contribution of various sources to the formation of hydrocarbon accumulations. The composition of their liquid component was formed as a result of the generation of hydrocarbons by the organic matter of Jurassic source rocks. The Lower and Middle Jurassic rocks with non-marine organic matter also made a significant contribution to the formation of the gas component of deposits in the north of Western Siberia, whereas the Cretaceous rocks generated only dry gas and were likely the main source of gas for the giant fields, whose methane has a light carbon isotope composition. The use of the isotopic composition of carbon in combination with molecular parameters makes it possible to clarify the conditions under which a particular field was formed and to elucidate the migration pathways and distances of hydrocarbon fluids to their accumulation sites. [ABSTRACT FROM AUTHOR]

New results on the radio-quiet type 2 quasar, known as the Teacup galaxy (SDSSJ1430+1339), based on the long-slit and 3D spectroscopic data obtained at the Russian 6-m telescope, are presented. The ionized gas giant nebula, which extends up to r = 56 kpc in the [O iii] emission line, was mapped with the scanning Fabry–Perot interferometer. The direct estimation of the emission line ratios confirmed that the giant nebula is ionized by the AGN. Stars in the inner r < 5 kpc are significantly younger than the outer host galaxy and have a solar metallicity. The central starburst age (∼1 Gyr) agrees with possible ages for the galactic merger events and the previous episode of the quasar outflow produced two symmetric arcs visible in the [O iii] emission at the distances r = 50–55 kpc. The ionized gas velocity field can be fitted by the model of a circular rotating disk significantly inclined or even polar to the stellar host galaxy. [ABSTRACT FROM AUTHOR]

Phosphine could be a key molecule in the understanding of exotic chemistry that occurs in (exo)planetary atmospheres. While phosphine has been detected in the Solar System's giant planets, it has not been observed in exoplanets to date. In the exoplanetary context, however, it has been theorized to be a potential biosignature molecule. The goal of our study was to identify which illustrative science cases for PH3 chemistry are observable with a space-based mid-infrared nulling interferometric observatory like the Large Interferometer for Exoplanets (LIFE) concept. We identified a representative set of scenarios for PH3 detections in exoplanetary atmospheres that vary over the whole dynamic range of the LIFE mission. We used chemical kinetics and radiative transfer calculations to produce forward models of these informative, prototypical observational cases for LIFEsim, our observation simulator software for LIFE. In a detailed, yet first order approximation, it takes a mission like LIFE: (i) about 1 h to find phosphine in a warm giant around a G star at 10 pc, (ii) about 10 h in H2 or CO2 dominated temperate super-Earths around M star hosts at 5 pc, (iii) and even in 100 h it seems very unlikely that phosphine would be detectable in a Venus-Twin with extreme PH3 concentrations at 5 pc. Phosphine in concentrations previously discussed in the literature is detectable in 2 out of the 3 cases, and it is detected about an order of magnitude faster than in comparable cases with James Webb Space Telescope. We show that there is a significant number of objects accessible for these classes of observations. These results will be used to prioritize the parameter range for the next steps with more detailed retrieval simulations. They will also inform timely questions in the early design phase of a mission like LIFE and guide the community by providing easy-to-scale first estimates for a large part of detection space of such a mission. [ABSTRACT FROM AUTHOR]

Hot giant exoplanets are very exotic objects with no equivalent in the Solar System that allow us to study the behavior of atmospheres under extreme conditions. Their thermal and chemical day–night dichotomies associated with extreme wind dynamics make them intrinsically 3D objects. Thus, the common 1D assumption, relevant to study colder atmospheres, reaches its limits in order to be able to explain hot and ultra-hot atmospheres and their evolution in a consistent way. In this review, we highlight the importance of these 3D considerations and how they impact transit, eclipse and phase curve observations. We also analyze how the models must adapt in order to remain self-consistent, consistent with the observations and sufficiently accurate to avoid bias or errors. We particularly insist on the synergy between models and observations in order to be able to carry out atmospheric characterizations with data from the new generation of instruments that are currently in operation or will be in the near future. [ABSTRACT FROM AUTHOR]

While giant planet occurrence rates increase with stellar mass, occurrence rates of close-in super-Earths decrease. This is in contradiction to the expectation that the total mass of the planets in a system scale with the protoplanetary disc mass and hence the stellar mass. Since the snow line plays an important role in the planet formation process, we examine differences in the temperature structure of protoplanetary gas discs around stars of different mass. Protoplanetary discs likely contain a dead zone at the mid-plane that is sufficiently cold and dense for the magneto-rotational instability to be suppressed. As material builds up, the outer parts of the dead zone may be heated by self-gravity. The temperature in the disc can be below the snow line temperature far from the star and in the inner parts of a dead zone. The inner icy region has a larger radial extent around smaller mass stars. The increased mass of solid icy material may allow for the in situ formation of larger and more numerous planets close to a low-mass star. Super-Earths that form in the inner icy region may have a composition that includes a significant fraction of volatiles. [ABSTRACT FROM AUTHOR]

Reservoir characterization is one of the key stages in oil and gas exploration, appraisal, development, and optimal production. During the exploration phase, core analysis and well logging are basic information obtained after the pay zone identification. This study aims to integrate the concept of electrofacies (EFs) with hydraulic flow units (HFUs) to effectively characterize Permo–Triassic carbonate formations at the Kangan giant gas field in southwestern Iran. For this purpose, well log data collected from 10 drilled wellbores and 490 core data have been analyzed based on similar clusters and statistical features in which rock-type approaches were used in order to integrate petrophysical data with facies. In particular, we used a multi-resolution graph-based clustering (MRGC) method to determine EFs and the probability plot method, histogram analysis, and the plot of reservoir quality index versus the normalized porosity to identify HFUs. Based on the data, five electrofacies and six HFUs were identified. To establish a good connection between the electrofacies and the pay zones, we analyzed wells' cross sections to compare lithology, production potential in each zone, rock type, and amount of shale and eventually to adapt facies to flow units and determine the best quality reservoir zone. The main difference between this work and other studies in the literature is adopting a systematic approach based on integrating the geology (via EFs analysis) and engineering examination (via HFUs) to accurately characterize the hydrocarbon-bearing formations. The results of this study help in rapid and cost-effective carbonate reservoir characterization by combining electrofacies clustering and HFU analysis based on core and log data, which are available and routine information in all oil/gas fields. This, in turn, assists in developing the field, using more appropriate production and EOR scenarios, and even locating proper perforation sites. [ABSTRACT FROM AUTHOR]

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It has been suggested that the occurrence rate of hot Jupiters (HJs) in open clusters might reach several per cent, significantly higher than that of the field (∼a per cent). In a stellar cluster, when a planetary system scatters with a stellar binary, it may acquire a companion star, which may excite large-amplitude von Zeipel–Lidov–Kozai oscillations in the planet's orbital eccentricity, triggering high-eccentricity migration, and the formation of an HJ. We quantify the efficiency of this mechanism by modelling the evolution of a gas giant around a solar mass star under the influence of successive scatterings with binary and single stars. We show that the chance that a planet ∈ (1, 10) au becomes an HJ in a Gyr in a cluster of stellar density n * = 50 pc−3, and binary fraction f bin = 0.5 is about 2 per cent and an additional 4 per cent are forced by the companion star into collision with or tidal disruption by the central host. An empirical fit shows that the total percentage of those outcomes asymptotically reaches an upper limit determined solely by f bin (e.g. 10 per cent at f bin = 0.3 and 18 per cent at f bin = 1) on a time-scale inversely proportional to n * (∼Gyr for n * ∼ 100 pc−3). The ratio of collisions to tidal disruptions is roughly a few, and depends on the tidal model. Therefore, if the giant planet occurrence rate is 10 per cent, our mechanism implies an HJ occurrence rate of a few times 0.1 per cent in a Gyr and can thus explain a substantial fraction of the observed rate. [ABSTRACT FROM AUTHOR]

Planets form in proto-planetary disks. In this review, we describe the structure and properties of such disks, and the various phenomenons that lead to the final product: a planetary system. First, micrometre dust settles and coagulates. Then, a complex interplay between the gas and centimetre aggregates leads to efficient phenomenons such as the streaming instability and the pebble accretion. Finally, gas accretion proceeds on ten Earth mass solid cores. Once the gas disk is dissipated, giant planets may form satellites from massive rings, the terrestrial planets assemble from smaller embryos, and global dynamical instabilities give the planetary systems their final architecture. [ABSTRACT FROM AUTHOR]

Understanding how giant and terrestrial planets form and evolve, what is their internal structure and that of their atmosphere, represents one of the major challenges of modern astronomy, which is directly connected to the ultimate search for life at the horizon 2030--2050. However, several astrophysical (understanding of the formation and physics of giant and terrestrial exoplanets), biological (identification of the best biomarkers) and technological (technical innovations for the new generations of telescopes and instruments) obstacles must be overcome. From the astrophysical point of view, it is indeed crucial to understand the mechanisms of formation and evolution of giant planets, including planet and disk interactions, which will completely sculpt the planetary architectures and thus dominate the formation of terrestrial planets, especially in regions around the host star capable of supporting life. It is also important to develop dedicated instrumentation and techniques to study in their totality the population of giant and terrestrial planets, but also to reveal in the near future the first biological markers of life in the atmospheres of terrestrial planets. In that perspective, direct imaging from ground-based observatories or in space is playing a central role in concert with other observing techniques. In this paper, I will briefly review the genesis of this observing technique, the main instrumental innovation and challenges, stellar targets and surveys, to then present the main results obtained so far about the physics and the mechanisms of formation and evolution of young giant planets and planetary system architectures. I will then present the exciting perspectives offered by the upcoming generation of planet imagers about to come online, particularly on the future extremely large telescopes. On the timescale of a human Life, we may well be witnessing the first discovery of an exoplanet and the first detection of indices of life in the atmosphere of a nearby exo-Earth! [ABSTRACT FROM AUTHOR]

This article provides a comprehensive overview of the study of exoplanets, planets outside of our solar system. It traces the historical development of this field and highlights the technological advancements that have enabled the detection and study of exoplanets. The article explores the diversity of exoplanets in terms of their physical and orbital properties, as well as their atmospheres. It emphasizes the need for further exploration and the development of new instruments and infrastructures to expand our understanding of exoplanets. The article also discusses the challenges in detecting and studying different types of exoplanets, and the ongoing search for life on Earth-like planets. Overall, it presents the study of exoplanets as a fascinating and ongoing endeavor for humanity. [Extracted from the article]

Recent detections of potentially habitable exoplanets around sunlike stars demand increased exploration of the physical conditions that can sustain life, by whatever methods available. Insight into these conditions can be gained by considering the multiverse hypothesis; in a multiverse setting, the probability of living in our universe depends on assumptions made about the factors affecting habitability. Various proposed habitability criteria can be systematically considered to rate each on the basis of their compatibility with the multiverse, generating predictions which can both guide expectations for life's occurrence and test the multiverse hypothesis. Here, we evaluate several aspects of planetary habitability, and show that the multiverse does indeed induce strong preferences among them. We find that the notion that a large moon is necessary for habitability is untenable in the multiverse scenario, as in the majority of parameter space, moons are not necessary to maintain stable obliquity. Further, we consider various proposed mechanisms for water delivery to the early Earth, including delivery from asteroids, both during giant planet formation and a grand tack, delivery from comets, and oxidation of a primary atmosphere by a magma ocean. We find that, depending on assumptions for how habitability depends on water content, some of these proposed mechanisms are disfavored in the multiverse scenario by Bayes factors of up to several hundred. [ABSTRACT FROM AUTHOR]

The outer planets of our Solar System display a myriad of interesting cloud features, of different colors and sizes. The differences between the types of observed clouds suggest a complex interplay between the dynamics and chemistry at play in these atmospheres. Particularly, the stark difference between the banded structures of Jupiter and Saturn vs. the sporadic clouds on the ice giants highlights the varieties in dynamic, chemical and thermal processes that shape these atmospheres. Since the early explorations of these planets by spacecrafts, such as Voyager and Voyager 2, there are many outstanding questions about the long-term stability of the observed features. One hypothesis is that the internal heat generated during the formation of these planets is transported to the upper atmosphere through latent heat release from convecting clouds (i.e., moist convection). In this review, we present evidence of moist convective activity in the gas giant atmospheres of our Solar System from remote sensing data, both from ground- and space-based observations. We detail the processes that drive moist convective activity, both in terms of the dynamics as well as the microphysical processes that shape the resulting clouds. Finally, we also discuss the effects of moist convection on shaping the large-scale dynamics (such as jet structures on these planets). [ABSTRACT FROM AUTHOR]

• The Earth generally records a higher fraction of carbonaceous (CC) material in more siderophile elements. • The last ∼2–10% of Earth's accretion involved CC-rich and volatile-rich material. • CC-rich embryos were implanted into the inner solar system early, but at least one struck the Earth when its accretion was almost complete. The nucleosynthetic isotope signatures of meteorites and the bulk silicate Earth (BSE) indicate that Earth consists of a mixture of "carbonaceous" (CC) and "non-carbonaceous" (NC) materials. We show that the fraction of CC material recorded in the isotopic composition of the BSE varies for different elements, and depends on the element's tendency to partition into metal and its volatility. The observed behavior indicates that the majority of material accreted to the Earth was NC-dominated, but that CC-dominated material enriched in moderately volatile elements by a factor of ∼10 was delivered during the last ∼2–10% of Earth's accretion. The late delivery of CC material to Earth contrasts with dynamical evidence for the early implantation of CC objects into the inner solar system during the growth and migration of the giant planets. This, together with the NC-dominated nature of both Earth's late veneer and bulk Mars, suggests that material scattered inwards had the bulk of its mass concentrated in a few, large CC embryos rather than in smaller planetesimals. We propose that Earth accreted a few of these CC embryos while Mars did not, and that at least one of the CC embryos impacted Earth relatively late (when accretion was 90–98% complete). This scenario is consistent with the subsequent Moon-forming impact of a large NC body, as long as this impact did not re-homogenize the entire Earth's mantle. [ABSTRACT FROM AUTHOR]

The formation history of Jupiter has been of interest due to its ability to shape the solar system's history. Yet little attention has been paid to the formation and growth of Saturn and the other giant planets. Here we explore through N -body simulations the implications of the simplest disc and pebble accretion model with steady-state accretion and an assumed ring structure in the disc at 5 AU on the formation of the giant planets in the solar system. We conducted a statistical survey of different disc parameters and initial conditions of the protoplanetary disc to establish which combination best reproduces the present outer solar system. We examined the effect of the initial planetesimal disc mass, the number of planetesimals and their size-frequency distribution slope, pebble accretion prescription and sticking efficiency on the likelihood of forming gas giants and their orbital distribution. The results reveal that the accretion sticking efficiency is the most sensitive parameter to control the final masses and number of giant planets. We have been unable to replicate the formation of all three types of giant planets in the solar system in a single simulation. The probability distribution of the final location of the giant planets is approximately constant in log r , suggesting there is a slight preference for formation closer to the Sun but no preference for more massive planets to form closer. The eccentricity distribution has a higher mean for more massive planets indicating that systems with more massive planets are more violent. We compute the average formation time for proto-Jupiter to reach 10 Earth masses to be 〈 t c , J 〉 = 1. 1 ± 0. 3 Myr and for proto-Saturn 〈 t c , S 〉 = 3. 3 ± 0. 4 Myr, while for the ice giants this increases to 〈 t c , I 〉 = 4. 9 ± 0. 1 Myr. The formation timescales of the cores of the gas giants are distinct at > 95 % confidence, suggesting that they formed sequentially. [ABSTRACT FROM AUTHOR]

We present the results of a study of secular resonances in a binary star system and their effects on the formation of terrestrial planets. The systems of our interest are binaries with moderate separations (i.e., smaller than 40 AU) where planets revolve around one of the stars. Using numerical simulations, we demonstrate the appearance and evolution of secular resonances in systems with two giant planets. Results indicate that the perturbation of the binary companion suppresses secular resonances and they do not play a significant role on the formation and orbital architecture of terrestrial planets. Unlike in our solar system where the secular resonance of Saturn confines the formation of terrestrial planets to regions interior to its location, in a binary star, terrestrial planets can form interior and exterior to this resonance. We present details of our simulations and discuss the implications of their results. [ABSTRACT FROM AUTHOR]

Using 2D hydrodynamical simulations, we show that in a low viscosity protoplanetary disc, Jupiter and Saturn get locked in the 2:1 mean motion resonance and migrate slowly inwards, unlike cases at higher viscosities. We conclude that in such discs the scenario of the Grand-Tack is not possible. Additionally, we investigate how the migration of the four (potentially five) giant planets in low viscous discs may affect the initial conditions of another important model for the formation history of our Solar System: the Nice Model. Adding ice giants in our hydrodynamical simulations, we find different possible resonant chains induced by migration. We then let the disc evolve until the gas phase dissipates and study the dynamical stability of the system. We find it possible to recreate the Solar System from such resonant chains, however the likelihood of this outcome remains low. [ABSTRACT FROM AUTHOR]