Understanding the large-scale dynamics of molecular clouds (MCs) is crucial for constraining the processes that govern star formation and the structure and evolution of the Galaxy. While gas tracers have traditionally been used to map MC kinematics, stellar tracers such as young stellar objects (YSOs) and open clusters (OCs) provide a complementary approach that enables direct comparisons between the stellar and gaseous components. We aim to validate OCs as complementary tracers by testing whether they retain the same bulk kinematic imprint as YSOs, and to reconstruct the three-dimensional (3D) motions of the main MC complexes within 2.5 kpc of the Sun using YSOs and young OCs as tracers. Using Gaia DR3 astrometry together with complementary spectroscopic surveys for radial velocities, we compiled a unified sample of 24,732 stellar tracers. We applied robust clustering in proper motion space to identify co-moving YSOs and derived cloud-averaged motions via Monte Carlo sampling. These were compared with the kinematics of OCs younger than 30 Myr. Finally, we performed orbital integrations in a realistic Galactic potential to trace the past evolution of the clouds and quantify their expansion and rotation. We derive homogeneous 3D kinematics for 15 MC complexes within 2.5 kpc. YSOs and OCs exhibit strongly consistent kinematics, with a median spatial velocity offset of ≃ 2 km s^-1, confirming that both populations trace the bulk motion of their parent clouds. The resulting cloud kinematics show a median peculiar velocity of ≃ 8.7 km s^-1 with respect to Galactic rotation. We trace back the Solar System's voyage through the Orion cloud and the common origin of Lupus, Ophiuchus, and Corona Australis in Sco-Cen. Internally, we detect significant expansion in Orion and Ophiuchus (5σ) and coherent rotation in at least seven complexes.

We review the current state of knowledge of the long-term evolution of the small bodies that give rise to comets and exocomets, as well as their reservoirs. The active cometary phase is only transitory, and bodies that become comets pass from a source population, such as the Kuiper Belt, Oort Cloud or their extra-solar analogues, through the active cometary phase, to eventual dormancy or destruction. We discuss dynamical delivery channels that can move comets from their source reservoirs to orbits with small periapsides, and the depletion of these reservoirs by dynamical and collisional means. We also discuss the physical evolution of cometary nuclei, especially in light of recent advances from missions to Solar System comets such as Rosetta's visit to 67P. We then describe our current knowledge of interstellar objects, which can originate from the same source regions as exocomets but be amenable to detailed study when they enter the Solar System. We include a summary of stellar winds emanating from different types of stars, which become increasingly strong once stars leave the Main Sequence. This is followed by a description of how small bodies are affected by stellar evolution, and the range of comet-like phenomena observed towards white dwarf stars. Overall, while we have an increasingly good picture of the physical and dynamical evolution of Solar System comets, a number of large gaps remain in our knowledge of the physics of exocomets, related to our inability to directly probe these bodies and many of the planets that might be affecting their orbits.

Small bodies exist in distinct populations within their planetary systems. These reservoir populations hold a range of compositions, which to first order are dependent on formation location relative to their star. We provide a general overview of the nature of the reservoirs that source exocomets, from the influence of the stellar environment through planetesimal formation to comparisons with Solar System populations. Once transitioned from a young protoplanetary disc to a debris disc, a star can expect to be rained with exocomets. While exocomets are predominantly detected to date at A-type stars, planetesimals plausibly exist across a range of stellar masses, based on exoplanet abundance, debris disc occurrence and white dwarf infall.

We present the detection and characterisation of the TOI-1438 multi-planet system discovered by the Transiting Exoplanet Survey Satellite (TESS). To confirm the planetary nature of the candidates and determine their masses, we collected a series of followup observations including high-spectral resolution observations with HARPS-N and HIRES over a period of 5 years. Our combined modelling shows that the K0V star hosts two transiting sub-Neptunes with R-b = 3.04 +/- 0.19 R-circle plus, R-c = 2.75 +/- 0.14 R-circle plus, M-b = 9.4 +/- 1.8 M-circle plus, and M-c =10.6 +/- 2.1 M-circle plus. The orbital periods of planets b and c are 5.1 and 9.4 days, respectively, corresponding to instellations of 145 +/- 10 F-circle plus and 65 +/- 4 F-circle plus. The bulk densities are 1.8 +/- 0.5 g cm(-3) and 2.9 +/- 0.7 g cm(-3), respectively, suggesting a volatile-rich interior composition. By combining the planet and stellar parameters, we were able to compute a set of planet interior structure models. Planet b presents a high-metallicity envelope that can accommodate up to 2.5% in H/He in mass, while planet c cannot have more than 0.2% as H/He in mass. For any composition of the core considered (Fe-rock or ice-rock), both planets would require a volatile-rich envelope. In addition to the two planets, the radial velocity (RV) data clearly reveal a third signal, likely coming from a non-transiting planet, with an orbital period of 7.6(-2.4)(+1.6) years and an RV semi-amplitude of 35(-5)(+3) m s(-1). Our best-fit model finds a minimum mass of 2.1 +/- 0.3 M-J and an eccentricity of 0.25(-0.11)(+0.08). However, several RV activity indicators also show strong signals at similar periods, suggesting this signal might (partly) originate from stellar activity. More data over a longer period of time are needed to conclusively determine the nature of this signal. If it is confirmed as a triple-planet system, TOI-1438 would be one of the few detected systems to date characterised by an architecture with two small, short-period planets and one massive, long-period planet, where the inner and outer systems are separated by an orbital period ratio of the order of a few hundred.

A star's luminosity increases as it evolves along the main sequence (MS), which inevitably results in a higher surface temperature for planets in orbit around the star. Technologically advanced civilizations may tackle this issue by installing artificial structures-starshades-which can reduce the radiation received by the planet. Starshades, if they exist, are potentially detectable with current or near-future technology. We have simulated phase curve signatures in direct imaging of hypothetical starshades in systems targeted by the upcoming Habitable Worlds Observatory (HWO), which will be tasked with searching for Earth-like exoplanets orbiting nearby stars. The starshade is assumed to be a circular, reflecting surface placed at the inner Lagrange point between the star and the planet. Our results show that the phase curve of a starshade has a distinct shape compared to that of a typical planet. The phase-curve signature lies above the expected 1 sigma = 10(-11) single-visit precision in contrast ratio of the telescope for 70 . 8 per cent of the target stars for the expected inner working angle (IWA) of around 60 mas. If the IWA can be reduced to 45 mas, the percentage of stars above the 1 sigma limit increases to 96 . 7 per cent . With a sufficiently small IWA, HWO should be able to detect anomalies in light curves caused by starshades or similar highly reflective surfaces-which could serve as key indicators for technologically advanced civilizations.

ABSTRACT Observations suggested that the occurrence rate of hot Jupiters (HJs) in open clusters is largely consistent with the field ($\sim 1{{\ \rm per\ cent}}$) but in the binary-rich cluster M67, the rate is $\sim 5{{\ \rm per\ cent}}$. How does the cluster environment boost HJ formation via the high-eccentricity tidal migration initiated by the extreme-amplitude von Zeipel–Lidov–Kozai (XZKL) mechanism forced by a companion star? Our analytical treatment shows that the cluster’s collective gravitational potential alters the companion’s orbit slowly, which may render the star–planet–companion configuration XZKL-favourable. We have also performed direct Gyr N-body simulations of the star cluster evolution and XZKL of planets’ orbit around member stars. We find that an initially single star may acquire a companion star via stellar scattering and the companion may enable XZKL in the planets’ orbit. Planets around an initially binary star may also be XZKL-activated by the companion. In both scenarios, the companion’s orbit has likely been significantly changed by stellar scattering and the cluster potential before XZKL occurs. Across different cluster models, 0.8–3 per cent of the planets orbiting initially single stars have experienced XZKL while the fraction is 2–26 per cent for initially binary stars. Around a star that is binary at 1 Gyr, 13–32 per cent of its planets have undergone XZKL, and combined with single stars, the overall XZKL fraction is 3–21 per cent, most affected by the cluster binarity. If 10 per cent of the stars in M67 host a giant planet, our model predicts an HJ occurrence rate of $\sim 1{{\ \rm per\ cent}}$. We suggest that HJ surveys target old, high-binarity, not-too-dense open clusters and prioritize wide binaries to maximize HJ yield.

Stars born in clusters are subject to frequent stellar flybys and so are their planets. The influence of an encounter reaches beyond the brief flyby itself in that the mutual forcing between the planets will continue to shape the planetary system in the long term and in a way that is impossible without the encounter in the first place. As a consequence, different planetary systems of different orbital scales and mass ranges behave differently as a result of the encounters. Here we study the encounters between two planetary systems where each star has its own planets using N-body simulations. Besides the immediate effect of the encounter, we have also propagated the systems post-encounter for up to 10^8 yr. See Figure 1 for an illustration.We find that immediately during the encounter, a planet can be ejected from its original host star. Here, the interplanetary interactions are negligible and a planet’s stellar-centric distance is a key factor. Only encounters closer than a few times that distance can cause strong disturbances, e.g., to eject the planet or to break the resonance in multi-planet systems. This means that close-in (

We report the discovery and characterization of a small planet, TOI-1408 c, on a 2.2 day orbit located interior to a previously known hot Jupiter, TOI-1408 b ( P = 4.42 days, M = 1.86 ± 0.02 M Jup , R = 2.4 ± 0.5 R Jup ) that exhibits grazing transits. The two planets are near 2:1 period commensurability, resulting in significant transit timing variations (TTVs) for both planets and transit duration variations for the inner planet. The TTV amplitude for TOI-1408 c is 15% of the planet’s orbital period, marking the largest TTV amplitude relative to the orbital period measured to date. Photodynamical modeling of ground-based radial velocity (RV) observations and transit light curves obtained with the Transiting Exoplanet Survey Satellite and ground-based facilities leads to an inner planet radius of 2.22 ± 0.06 R ⊕ and mass of 7.6 ± 0.2 M ⊕ that locates the planet into the sub-Neptune regime. The proximity to the 2:1 period commensurability leads to the libration of the resonant argument of the inner planet. The RV measurements support the existence of a third body with an orbital period of several thousand days. This discovery places the system among the rare systems featuring a hot Jupiter accompanied by an inner low-mass planet.

TOI-732 is an M dwarf hosting two transiting planets that are located on the two opposite sides of the radius valley. By doubling the number of available space-based observations and increasing the number of radial velocity (RV) measurements, we aim at refining the parameters of TOI-732 b and c. We also use the results to study the slope of the radius valley and the density valley for a well-characterised sample of M-dwarf exoplanets. We performed a global MCMC analysis by jointly modelling ground-based light curves and CHEOPS and TESS observations, along with RV time series both taken from the literature and obtained with the MAROON-X spectrograph. The slopes of the M-dwarf valleys were quantified via a Support Vector Machine (SVM) procedure. TOI-732 b is an ultrashort-period planet ($P\sim0.77$ d) with a radius $R_b=1.325_{-0.058}^{+0.057}$ $R_{\oplus}$ and a mass $M_b=2.46\pm0.19$ $M_{\oplus}$ (mean density $\rho_b=5.8_{-0.8}^{+1.0}$ g cm$^{-3}$), while the outer planet at $P\sim12.25$ d has $R_c=2.39_{-0.11}^{+0.10}$ $R_{\oplus}$, $M_c=8.04_{-0.48}^{+0.50}$ $M_{\oplus}$, and thus $\rho_c=3.24_{-0.43}^{+0.55}$ g cm$^{-3}$. Also taking into account our interior structure calculations, TOI-732 b is a super-Earth and TOI-732 c is a mini-Neptune. Following the SVM approach, we quantified $\mathrm{d}\log{R_{p,{\mathrm{valley}}}}/\mathrm{d}\log{P}=-0.065_{-0.013}^{+0.024}$, which is flatter than for Sun-like stars. In line with former analyses, we note that the radius valley for M-dwarf planets is more densely populated, and we further quantify the slope of the density valley as $\mathrm{d}\log{\hat{\rho}_{\mathrm{valley}}}/\mathrm{d}\log{P}=-0.02_{-0.04}^{+0.12}$. Compared to FGK stars, the weaker dependence of the position of the radius valley on the orbital period might indicate that the formation shapes the radius valley around M dwarfs more strongly than the evolution mechanisms.

Several stars show deep transits consistent with discs of roughly 1 Solar radius seen at moderate inclinations, likely surrounding planets on eccentric orbits. We show that this configuration arises naturally as a result of planet-planet scattering when the planets possess satellite systems. Planet-planet scattering explains the orbital eccentricities of the discs' host bodies, while the close encounters during scattering lead to the exchange of satellites between planets and/or their destabilisation. This leads to collisions between satellites and their tidal disruption close to the planet. Both of these events lead to large quantities of debris being produced, which in time will settle into a disc such as those observed. The mass of debris required is comparable to a Ceres-sized satellite. Through N-body simulations of planets with clones of the Galilean satellite system undergoing scattering, we show that 90 percent of planets undergoing scattering will possess debris from satellite destruction. Extrapolating to smaller numbers of satellites suggests that tens of percent of such planets should still possess circumplanetary debris discs. The debris trails arising from these events are often tilted at tens of degrees to the planetary orbit, consistent with the inclinations of the observed discs. Disruption of satellite systems during scattering thus simultaneously explains the existence of debris, the tilt of the discs, and the eccentricity of the planets they orbit.

Understanding stellar evolution and its effect on planetary systems is crucial for correctly interpreting the chemical constraints of exo-planetary material that can be given to us by white dwarfs. This article will describe how asteroids, moons, and comets, as well as boulders, pebbles and dust, evolve into eventual targets for chemical spectroscopy, and how planets and companion stars play a vital role in reshaping system architectures for this purpose.

Context. M-dwarf stars are the most common of potential exoplanet host stars in the Galaxy. It is therefore very important to understand planetary systems orbiting such stars and to determine the physical parameters of such planets with high precision. Also with the launch of the James Webb Space Telescope (JWST) the observation of atmospheric parameters of planets orbiting these stars has begun. It is therefore required to determine properties of potential targets. Aims. Two planets around the red dwarf TOI-776 were detected by TESS. The objective of our study was to use transit observations obtained by the CHEOPS space mission to improve the current precision of the planetary radii, as well as additional radial velocity (RV) data in order to improve mass estimates of the two planets. Using these quantities, we wanted to derive the bulk densities of those planets, improving the precision in earlier results, and use this information to put them in context of other exoplanetary systems involving very low mass stars. Methods. Utilizing new transit data from the CHEOPS satellite and its photometric telescope, we obtained very high precision planetary transit measurements. Interpretation of these provides updated planetary radii, along with other system parameters. A concurrent ESO large observing program using the high precision spectrograph HARPS has doubled the available radial velocity data. Calculating the power spectrum of a number of stellar activity indices we update the previously estimated stellar rotation period to a lower value. Results. The CHEOPS data provide precise transit depths of 909 and 1177 ppm translating into radii of R b = 1.798 −0.077 +0.078 R ⊕ and R c = 2.047 −0.078 +0.081 R ⊕ , respectively. Our interpretation of the radial velocities and activity indicator time series data estimates a stellar rotation period for this early M dwarf of ~21.1 days. A further multi-dimensional Gaussian process approach confirm this new estimate. By performing a Skew-Normal (SN) fit onto the Cross Correlation Functions we extracted the RV data and the activity indicators to estimate the planetary masses, obtaining M b = 5.0 −1.6 +1.6 M ⊕ and M c = 6.9 −2.5 +2.6 M ⊕ . Conclusions. We improve the precision in planetary radius for TOI-776 b and c by a factor of more than two. Our data and modelling give us parameters of both bodies consistent with mini-Neptunes, albeit with a relatively high density. The stellar activity of TOI-776 is found to have increased by a factor larger than 2 since the last set of observations.

GJ 367 is a bright ( V ≈ 10.2) M1 V star that has been recently found to host a transiting ultra-short period sub-Earth on a 7.7 hr orbit. With the aim of improving the planetary mass and radius and unveiling the inner architecture of the system, we performed an intensive radial velocity follow-up campaign with the HARPS spectrograph—collecting 371 high-precision measurements over a baseline of nearly 3 yr—and combined our Doppler measurements with new TESS observations from sectors 35 and 36. We found that GJ 367 b has a mass of M b = 0.633 ± 0.050 M ⊕ and a radius of R b = 0.699 ± 0.024 R ⊕ , corresponding to precisions of 8% and 3.4%, respectively. This implies a planetary bulk density of ρ b = 10.2 ± 1.3 g cm −3 , i.e., 85% higher than Earth’s density. We revealed the presence of two additional non-transiting low-mass companions with orbital periods of ∼11.5 and 34 days and minimum masses of M c sin i c = 4.13 ± 0.36 M ⊕ and M d sin i d = 6.03 ± 0.49 M ⊕ , respectively, which lie close to the 3:1 mean motion commensurability. GJ 367 b joins the small class of high-density planets, namely the class of super-Mercuries, being the densest ultra-short period small planet known to date. Thanks to our precise mass and radius estimates, we explored the potential internal composition and structure of GJ 367 b, and found that it is expected to have an iron core with a mass fraction of 0.91 − 0.23 + 0.07 . How this iron core is formed and how such a high density is reached is still not clear, and we discuss the possible pathways of formation of such a small ultra-dense planet.

Abstract Many important advances in planet formation theory have come from the discovery of unexpected planets. The thousands of discovered exoplanets have unveiled demographic trends, such as the bimodality of planetary radius distribution known as the radius valley. Modelling these trends can probe underlying processes, e.g. the formation environment and atmospheric evolution. Here, we report the discovery and characterisation of a four-planet system around the kinematically thick-disk M-dwarf LHS 1903 with orbital periods of 2.16, 6.23, 12.57, and 29.32 days that becomes the only known M-dwarf hosting four small, well-characterised planets spanning the radius valley. We utilise high-precision transit photometry from the Transiting Exoplanet Survey Satellite (TESS) and the CHaracterising ExOPlanets Satellite (CHEOPS) to measure the radii of LHS 1903 b, c, d, and e (1.382+/-0.046, 2.046^+0.078_-0.074, 2.500^+0.078_-0.077, and 1.732^+0.059_-0.058 R_oplus). Combined with HARPS-N radial velocity data, we determine the planetary bulk densities (1.24^+0.21_-0.19, 0.53^+0.11_-0.09, 0.38^+0.09_-0.08, and 1.11^+0.33_-0.31 rho_oplus). Our compositional analysis finds that planet b is rocky, planets c and d have extended atmospheres, and LHS 1903 e does not have a gaseous envelope. Our discovery that planet e, the longest-period well-characterised terrestrial M-dwarf planet, lacks an extended atmosphere causes tension with thermally-driven mass loss radius valley predictions, but supports a gas-depleted formation explanation. The observed broken atmospheric-mass fraction trend is at odds with current formation theory, but provides further evidence for a gas-depleted formation environment for terrestrial M-dwarf planets.

The TOI-1130 is a known planetary system around a K-dwarf consisting of a gas giant planet, TOI-1130 c on an 8.4-day orbit that is accompanied by an inner Neptune-sized planet, TOI-1130 b, with an orbital period of 4.1 days. We collected precise radial velocity (RV) measurements of TOI-1130 with the HARPS and PFS spectrographs as part of our ongoing RV follow-up program. We performed a photodynamical modeling of the HARPS and PFS RVs, along with transit photometry from the Transiting Exoplanet Survey Satellite (TESS) and the TESS Follow-up Observing Program (TFOP). We determined the planet masses and radii of TOI-1130 b and TOI-1130 c to be Mb = 19.28 ± 0.97M⊕ and Rb = 3.56 ± 0.13 R⊕, and Mc = 325.59 ± 5.59M⊕ and Rc = 13.32−1.41+1.55 R⊕, respectively. We have spectroscopically confirmed the existence of TOI-1130 b, which had previously only been validated. We find that the two planets have orbits with small eccentricities in a 2:1 resonant configuration. This is the first known system with a hot Jupiter and an inner lower mass planet locked in a mean-motion resonance. TOI-1130 belongs to the small, yet growing population of hot Jupiters with an inner low-mass planet that poses a challenge to the pathway scenario for hot Jupiter formation. We also detected a linear RV trend that is possibly due to the presence of an outer massive companion.

ABSTRACT 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 fbin = 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 fbin (e.g. 10 per cent at fbin = 0.3 and 18 per cent at fbin = 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.

Among the hundreds of known hot Jupiters (HJs), only five have been found to have companions on short-period orbits. Within this rare class of multiple planetary systems, the architecture of WASP-47 is unique, hosting an HJ (planet -b) with both an inner and an outer sub-Neptunian mass companion (-e and -d, respectively) as well as an additional non-transiting, long-period giant (-c). The small period ratio between planets -b and -d boosts the transit time variation (TTV) signal, making it possible to reliably measure the masses of these planets in synergy with the radial velocity (RV) technique. In this paper, we present new space- and ground-based photometric data of WASP-47b and WASP-47-d, including 11 unpublished light curves from the ESA mission CHEOPS. We analyzed the light curves in a homogeneous way together with all the publicly available data to carry out a global $N$-body dynamical modeling of the TTV and RV signals. We retrieved, among other parameters, a mass and density for planet -d of $M_\mathrm{d}=15.5\pm 0.8$ $M_\oplus$ and $\rho_\mathrm{d}=1.69\pm 0.22$ g\,cm$^{-3}$, which is in good agreement with the literature and consistent with a Neptune-like composition. For the inner planet (-e), we found a mass and density of $M_\mathrm{e}=9.0\pm 0.5$ $M_\oplus$ and $\rho_\mathrm{e}=8.1\pm 0.5$ g\,cm$^{-3}$, suggesting an Earth-like composition close to other ultra-hot planets at similar irradiation levels. Though this result is in agreement with previous RV+TTV studies, it is not in agreement with the most recent RV analysis (at 2.8$\sigma$), which yielded a lower density compatible with a pure silicate composition. This discrepancy highlights the still unresolved issue of suspected systematic offsets between RV and TTV measurements. In this paper, we also significantly improve the orbital ephemerides of all transiting planets, which will be crucial for any future follow-up.

ABSTRACT A large fraction of stars are formed in dense clusters. In the cluster, close encounters between stars at distances less than 100 au are common. It has been shown that during close encounters planets can transfer between stars. Such captured planets will be on different orbits compared to planets formed in the system, often on very wide, eccentric, and inclined orbits. We examine how these captured planets affect Kuiper belt-like planetesimal belts in their new systems by examining the effects on habitable planets in systems containing an outer gas giant. We show that these captured planets can destabilize the belt, and we show that the fraction of the planetesimals that make it past the giant planets into the system to impact the habitable planet is independent of the captured planet’s orbital plane, whereas the fraction of the planetesimals that are removed and the rate at which they are removed depend strongly on the captured planet’s pericentre and inclination. We then examine a wide range of outcomes of planet capture and find that when a Jupiter-mass planet is captured it will in 40 per cent of cases destabilize the giant planets in the system and in 40 per cent of cases deplete the belt in a few Myr, i.e. not posing much risk to life on terrestrial planets that would be expected to develop later. In the final 20 per cent of cases, the result will be a flux of impactors 10–20 times greater than that on Earth that can persist for several Gyr, detrimental to the development of life on the planet.

Context. The birth environments of planetary systems are thought to influence planet formation and orbital evolution, through external photoevaporation and stellar flybys. Recent work has claimed observational support for this, in the form of a correlation between the properties of planetary systems and the local Galactic phase space density of the host star. In particular, Hot Jupiters are found overwhelmingly around stars in regions of high phase space density, which may reflect a formation environment with high stellar density. Aims. We instead investigate whether the high phase space density may have a galactic kinematic origin: Hot Jupiter hosts may be biased towards being young and therefore kinematically cold, because tidal inspiral leads to the destruction of the planets on Gyr timescales, and the velocity dispersion of stars in the Galaxy increases on similar timescales. Methods. We use 6D positions and kinematics from Gaia for the Hot Jupiter hosts and their neighbours, and construct distributions of the phase space density. We investigate correlations between the stars' local phase space density and peculiar velocity. Results. We find a strong anticorrelation between the phase space density and the host star's peculiar velocity with respect to the Local Standard of Rest. Therefore, most stars in"high-density"regions are kinematically cold, which may be caused by the aforementioned bias towards detecting Hot Jupiters around young stars before the planets' tidal destruction. Conclusions. We do not find evidence in the data for Hot Jupiter hosts preferentially being in phase space overdensities compared to other stars of similar kinematics, nor therefore for their originating in birth environments of high stellar density.

The recently discovered giant exoplanet IIR5183b exists on a wide, highly eccentric orbit (a = 18 au, e = 0.84). Its host star possesses a common proper-motion companion which is likely on a bound orbit. In this paper, we explore scenarios for the excitation of the eccentricity of the planet in binary systems such as this, considering planet-planet scattering, Lidov-Kozai cycles from the binary acting on a single-planet system, or Lidov-Kozai cycles acting on a two-planet system that also undergoes scattering. Planet-planet scattering, in the absence of a binary companion, has a 2.8-7.2 per cent probability of pumping eccentricities to the observed values in our simulations, depending on the relative masses of the two planets. Lidov-Kozai cycles from the binary acting on an initially circular orbit can excite eccentricities to the observed value but require very specific orbital configurations for the binary and overall there is a low probability of catching the orbit at the high observed high eccentricity (0.6 per cent). The best case is provided by planet-planet scattering in the presence of a binary companion: here, the scattering provides the surviving planet with an initial eccentricity boost that is subsequently further increased by Kozai cycles from the binary. We find a success rate of 14.5 per cent for currently observing e >= 0.84 in this set-up. The single-planet plus binary and two-planet plus binary cases are potentially distinguishable if the mutual inclination of the binary and the planet can be measured, as the latter permits a broader range of mutual inclinations. The combination of scattering and Lidov-Kozai forcing may also be at work in other wide-orbit eccentric giant planets, which have a high rate of stellar binary companions.