Planetary Systems Research Articles

Tolerance analysis of slat gear rotary actuator in civil aircraft

Abstract The slat gear rotary actuator of civil aircraft needs to meet the requirements of small space and large transmission ratio. The planetary gear system based on triple teeth is a common actuator design, and the design structure is complex, so its tolerance control is also strict. In order to meet the design requirements of its internal structure, this paper presents a deviation analysis method for the internal structure design of a typical civil aircraft slat gear rotary actuator. The results of preliminary tolerance distribution and improved tolerance distribution are analyzed using the Jacobi-based assembly deviation model. By comparing the standard deviation of the analysis results, the validity of this deviation analysis method is verified, which proves that this method can be used to analyze the internal structure deviation of the rotary actuator of slat gear in civil aircraft.

2023 DZ2 Planetary Defense Campaign

We present the results of a fourth planetary defense exercise, focused this time on the small near-Earth asteroid (NEA) 2023 DZ2 and conducted during its close approach to the Earth in 2023 March. The International Asteroid Warning Network (IAWN), with support from NASA's Planetary Defense Coordination Office (PDCO), has been coordinating planetary defense observational campaigns since 2017 to test the operational readiness of the global planetary defense capabilities. The last campaign focused on the NEA Apophis, and an outcome of that exercise was the need for a short burst campaign to replicate a real-life near-Earth object impact hazard scenario. The goal of the 2023 DZ2 campaign was to characterize the small NEA as a potential impactor and exercise the planetary defense system including observations, hypothetical risk assessment and risk prediction, and hazard communication with a short notice of just 24 hr. The entire campaign lasted about 10 days. The campaign team was divided into several working groups based on the characterization method: photometry, spectroscopy, thermal IR photometry and optical polarimetry, radar, and risk assessment. Science results from the campaign show that 2023 DZ2 has a rotation period of 6.2745 ± 0.0030 minutes; visible wavelength color photometry/spectroscopy/polarimetry and near-IR spectroscopy all point to an E-type taxonomic classification with surface composition analogous to aubrite meteorites; and radar observations show that the object has a diameter of 30 ± 10 m, consistent with the high albedo (0.49) derived from polarimetric and thermal IR observations.

Fast formation of large ice pebbles after FU Orionis outbursts

During their formation, nascent planetary systems are subject to FU Orionis outbursts that heat a substantial part of the disc. This causes water ice in the affected part of the disc to sublimate as the ice line moves outwards to several to tens of astronomical units. In this paper, we investigate how the subsequent cooling of the disc impacts the particle sizes. We calculate the resulting particle sizes in a disc model with cooling times between 100 and 1000 yr, corresponding to typical FU Orionis outbursts. As the disc cools and the ice line retreats inwards, water vapour forms icy mantles on existing silicate particles. This process is called heterogeneous nucleation. The nucleation rate per surface area of silicate substrate strongly depends on the degree of super-saturation of the water vapour in the gas. Fast cooling results in high super-saturation levels, high nucleation rates, and limited condensation growth because the main ice budget is spent in the nucleation. Slow cooling, on the other hand, leads to rare ice nucleation and efficient growth of ice-nucleated particles by subsequent condensation. We demonstrate that close to the quiescent ice line, pebbles with a size of about centimetres to decimetres form by this process. The largest of these are expected to undergo cracking collisions. However, their Stokes numbers still reach values that are high enough to potentially trigger planetesimal formation by the streaming instability if the background turbulence is weak. Stellar outbursts may thus promote planetesimal formation around the water ice line in protoplanetary discs.

No Signature of the Birth Environment of Exoplanets from Their Host Stars’ Mahalanobis Phase Space

The architectures of extrasolar planetary systems often deviate considerably from the “standard” model for planet formation, which is largely based on our own solar system. In particular, gas giants on close orbits are not predicted by planet formation theory and so some processes are thought to move the planets closer to their host stars. Recent research has suggested that hot-Jupiter host stars display a different phase space compared to stars that do not host hot Jupiters. This has been attributed to these stars forming in star-forming regions of high stellar density, where dynamical interactions with passing stars have perturbed the planets. We test this hypothesis by quantifying the phase space of planet-hosting stars in dynamical N-body simulations of star-forming regions. We find that stars that retain their planets have a higher phase space than nonhosts, regardless of their initial physical density. This is because an imprint of the kinematic substructure from the regions birth is retained, as these stars have experienced fewer and less disruptive encounters than stars whose planets have been liberated and become free-floating. However, host stars whose planets remain bound but have had their orbits significantly altered by dynamical encounters are also primarily found in high phase space regimes. We therefore corroborate other research in this area that has suggested the high phase space of hot-Jupiter host stars is not caused by dynamical encounters or stellar clustering, but rather reflects an age bias in that these stars are (kinematically) younger than other exoplanet host stars.

Characterisation of the TOI-421 planetary system using CHEOPS, TESS, and archival radial velocity data

Context. The TOI-421 planetary system contains two sub-Neptune-type planets (Pb ~ 5.2 days, Teq,b ~ 900 K, and Pc ~ 16.1 days, Teq,c ~ 650 K) and is a prime target to study the formation and evolution of planets and their atmospheres. The inner planet is especially interesting as the existence of a hydrogen-dominated atmosphere at its orbital separation cannot be explained by current formation models without previous orbital migration. Aims. We aim to improve the system parameters to further use them to model the interior structure and simulate the atmospheric evolution of both planets, to finally gain insights into their formation and evolution. We also investigate the possibility of detecting transit timing variations (TTVs). Methods. We jointly analysed photometric data of three TESS sectors and six CHEOPS visits as well as 156 radial velocity data points to retrieve improved planetary parameters. We also searched for TTVs and modelled the interior structure of the planets. Finally, we simulated the evolution of the primordial H-He atmospheres of the planets using two different modelling frameworks. Results. We determine the planetary radii and masses of TOI-421 b and c to be Rb = 2.64 ± 0.08 R⊕, Mb = 6.7 ± 0.6 M⊕, Rc = 5.09 ± 0.07 R⊕, and Mc = 14.1 ± 1.4 M⊕. Using these results we retrieved average planetary densities of ρb = 0.37 ± 0.05ρ⊕ and ρc = 0.107 ± 0.012 ρ⊕. We do not detect any statistically significant TTV signals. Assuming the presence of a hydrogen-dominated atmosphere, the interior structure modelling results in both planets having extensive envelopes. While the modelling of the atmospheric evolution predicts for TOI-421 b to have lost any primordial atmosphere that it could have accreted at its current orbital position, TOI-421 c could have started out with an initial atmospheric mass fraction somewhere between 10 and 35%. Conclusions. We conclude that the low observed mean density of TOI-421 b can only be explained by either a bias in the measured planetary parameters (e.g. driven by high-altitude clouds) and/or in the context of orbital migration. We also find that the results of atmospheric evolution models are strongly dependent on the employed planetary structure model.

Uranus’s Influence on Neptune’s Exterior Mean-motion Resonances

Neptune’s external mean-motion resonances play an important role in sculpting the observed population of trans-Neptunian objects (TNOs). The population of scattering TNOs is known to “stick” to Neptune's resonances while evolving in semimajor axis (a), though simulations show that resonance sticking is less prevalent at a ≳ 200–250 au. Here we present an extensive numerical exploration of the strengths of Neptune's resonances for scattering TNOs with perihelion distances q = 33 au. We show that the drop-off in resonance sticking for the large a scattering TNOs is not a generic feature of scattering dynamics but can instead be attributed to the specific configuration of Neptune and Uranus in our solar system. In simulations with just Uranus removed from the giant planet system, Neptune's resonances are strong in the scattering population out to at least ∼300 au. Uranus and Neptune are near a 2:1 period ratio, and the variations in Neptune's orbit resulting from this near-resonance are responsible for destabilizing Neptune's resonances for high-e TNO orbits beyond the ∼20:1 resonance at a ≈ 220 au. Direct interactions between Uranus and the scattering population are responsible for slightly weakening Neptune's closer-in resonances. In simulations where Neptune and Uranus are placed in their mutual 2:1 resonance, we see almost no stable libration of scattering particles in Neptune's external resonances. Our results have important implications for how the strengths of Neptune's distant resonances varied during the epoch of planet migration when the Neptune–Uranus period ratio was evolving. These strength variations likely affected the distant scattering, resonant, and detached TNO populations.

A Comprehensive Analysis of the Habitability of TRAPPIST-1 Exoplanets

TRAPPIST-1 is the most studied star system other than our Solar System. The announcement of the discovery of the system fostered international attention for its potential to harbor extraterrestrial life, and maybe one day even human life. This paper aims to evaluate the validity of this excitement by interpreting and compiling all available information regarding factors that could potentially affect habitability. To do this, we look at all data regarding the Habitable Zone and Water Presence, Tidal Forces, and Atmospheric Composition resulting in Extreme UV (EUV) Flux. Specifically, we compare Transmission spectra of the four planets in the habitable zone with synthetic, potentially habitable atmospheres, we compare composition and density of the planets with Earth and other density models to determine water composition, and we consider both high and low stellar activity to determine EUV flux in an anoxic, Earth-like and very thin atmosphere. This paper shows that on net, due to the lack of a thick atmosphere, various issues arise that lead to the conclusion that the planetary system is uninhabitable for even the most resistant terrestrial organisms. This set of considerations could be used in studying other planetary systems and evaluating their habitability as well.

Smart nodding duck: A hybrid Halbach electromagnetic piezoelectric self-powered sensor for smart fisheries

Wave energy harvesting plays a crucial part in promoting the sustainable development of marine fisheries. This paper presents a novel hybrid electromagnetic and piezoelectric Self-powered Sensor, known as the Smart Nodding Duck (SND). The SND consists primarily of two components: an electromagnetic generator (EMG) responsible for power generation and a piezoelectric generator (PEG) dedicated to monitoring purposes. The SND absorbs wave energy through the shell of the nodding duck, while the planetary wheel system forms a coaxial counter-rotating augmentation structure. Also, the Halbach magnetic array serves as the electromagnetic generator, simultaneously exciting the piezoelectric structure to generate voltage signals. These features enable the SND to contribute to the LSTM network modeling self-sensing system, facilitating the monitoring of sea states. To verify the power generation effect of the SND, we conducted bench tests. The results demonstrate that the electromagnetic generator achieves an average output power of 96.26mW under a wave excitation of 0.8 Hz with an amplitude of 80 mm, yielding a power density of 16 W/m3. Furthermore, the self-sensing sea state monitoring model exhibits an impressive accuracy of 99.3 %. Moreover, tank experiment verified the feasibility of the SND, further contributing to the construction of a smart marine fishery Internet of Things.

JWST imaging of the closest globular clusters—I. Possible infrared excess among white dwarfs in NGC 6397

AbstractWe present James Webb Space Telescope observations of the globular cluster NGC 6397 and use them to extend to infrared wavelengths the characterization of the cluster's entire white dwarf (WD) cooling sequence (CS). The data allows us to probe fundamental astrophysical WD properties and to search for evidence in their colors for (or against) the existence of ancient planetary systems. The existing archival Hubble Space Telescope imaging data obtained years ago reach ultra‐deep optical magnitudes () and allow us to derive a near‐perfect separation between field and cluster members. We detect an apparent split in the lower part of the WD CS of NGC 6397. The red part of the WD CS, containing about 25% of the total, exhibits significant IR‐excess of up to mag. These infrared excesses require both theoretical and observational follow‐ups to confirm their veracity and to ascertain their true nature.

Analysis of the Dynamic Characteristics of Coaxial Counter-Rotating Planetary Transmission System

This paper presents a coaxial counter-rotating planetary transmission system. The transmission system under study is a two-stage planetary gear train (PGT) comprising a fixed-axes PGT and a differential PGT. A dynamic model of the transmission system is established, considering both the excitations caused by the time-varying mesh stiffness (TMS) and the transmission errors, respectively. The Runge–Kutta algorithm is used to calculate and analyze the dynamic characteristics of the system. This includes studying dynamic meshing forces, planet gear displacements, and load-sharing coefficients (LSCs) under both internal and external excitations, as well as different input torques. The results indicate that when considering external excitations, the variations in the meshing force curves become more pronounced. The radial displacements of the planet gears in the differential PGT are greater than that in the fixed-axes PGT. With increasing input torque, the average displacements of the planet gears in all directions tend to increase. The differential PGT, transmitting a higher power, demonstrates a better load-sharing performance compared to the fixed-axes PGT.

Resonant chains in triple-planet systems

The mean motion resonance is the most important mechanism that may dominate the dynamics of a planetary system. In a multi-planetary system consisting of $N planets, the planets may form a resonant chain when the ratios of orbital periods of planets can be expressed as the ratios of small integers $T_1: T_2: :T_N=k_1: k_2: k_N$. Due to the high degree of freedom, the motion in such systems could be complex and difficult to depict. In this paper, we investigate the dynamics and possible formation of the resonant chain in a triple-planet system. We defined the appropriate Hamiltonian for a three-planet resonant chain and numerically averaged it over the synodic period. The stable stationary solutions -- apsidal corotational resonances (ACRs) -- of this averaged system, corresponding to the local extrema of the Hamiltonian function, can be searched out numerically. The topology of the Hamiltonian around these ACRs reveals their stabilities. We further constructed the dynamical maps on different representative planes to study the dynamics around the stable ACRs, and we calculated the deviation ($ of the resonant angle in the evolution from the uniformly distributed values, by which we distinguished the behaviour of critical angles. Finally, the formation of the resonant chain via convergent planetary migration was simulated and the stable configurations associated with ACRs were verified. We find that the stable ACR families arising from circular orbits always exist for any resonant chain, and they may extend to a high eccentricity region. Around these ACR solutions, regular motion can be found, typically in two types of resonant configurations. One is characterised by libration of both the two-body resonant angles and the three-body Laplace resonant angle, and the other by libration of only two-body resonant angles. The three-body Laplace resonance does not seem to contribute to the stability of the resonant chain much. The resonant chain can be formed via convergent migration, and the resonant configuration evolves along the ACR families to eccentric orbits once the planets are captured into the chain. Ideally, our methods introduced in this paper can be applied to any resonant chain of any number of planets at any eccentricity.

Nuance: Efficient Detection of Planets Transiting Active Stars

The detection of planetary transits in the light curves of active stars, featuring correlated noise in the form of stellar variability, remains a challenge. Depending on the noise characteristics, we show that the traditional technique that consists of detrending a light curve before searching for transits alters their signal-to-noise ratio and hinders our capability to discover exoplanets transiting rapidly rotating active stars. We present nuance, an algorithm to search for transits in light curves while simultaneously accounting for the presence of correlated noise, such as stellar variability and instrumental signals. We assess the performance of nuance on simulated light curves as well as on the Transiting Exoplanet Survey Satellite light curves of 438 rapidly rotating M dwarfs. For each data set, we compare our method to five commonly used detrending techniques followed by a search with the Box-Least-Squares algorithm. Overall, we demonstrate that nuance is the most performant method in 93% of cases, leading to both the highest number of true positives and the lowest number of false-positive detections. Although simultaneously searching for transits while modeling correlated noise is expected to be computationally expensive, we make our algorithm tractable and available as the JAX-powered Python package nuance, allowing its use on distributed environments and GPU devices. Finally, we explore the prospects offered by the nuance formalism and its use to advance our knowledge of planetary systems around active stars, both using space-based surveys and sparse ground-based observations.

Leisure and the Anthropocene—Special Issue Introduction

The Anthropocene, introduced by scientists in 2000 to name the current geological epoch, draws attention to the scale and force of anthropogenic impacts on Earth systems. With this special issue, we aim to inspire and assemble scholarship that has an intentional focus on understanding, critiquing, and (re)imagining relationships between leisure and the Anthropocene. More specifically, we have invited contributing authors to explore questions such as: how is the field of leisure studies grappling with global ecological crises? How does leisure matter in the Anthropocene? How has leisure been complicit in producing the Anthropocene? How might leisure help heal, or inflict further damage to, human and more-than-human relations within planetary systems? This article introduces the special issue by presenting brief background information for readers and illuminating three cross-cutting themes within the special issue manuscripts, namely: (a) times, temporalities, and rhythms; (b) ethical relationships and responsibilities; and (c) “new” sensibilities.

An Eccentric Planet Orbiting the Polar V808 Aurigae

We analyze 15 yr of eclipse timings of the polar V808 Aur. The rapid ingress/egress of the white dwarf and bright accretion region provide timings as precise as a few tenths of a second for rapid cadence photometric data. We find that between 2015 and 2018, the eclipse timings deviated from a linear ephemeris by more than 30 s. The rapid timing change is consistent with the periastron passage of a planet in an eccentric orbit about the polar. The best-fit orbital period is 11 ± 1 yr and we estimate a projected mass of Msin(i)=6.8±0.7 Jupiter masses. We also show that the eclipse timings are correlated with the brightness of the polar with a slope of 1.1 s mag−1. This is likely due to the change in the geometry of the accretion curtains as a function of the mass transfer rate in the polar. While an eccentric planet offers an excellent explanation to the available eclipse data for V808 Aur, proposed planetary systems in other eclipsing polars have often struggled to accurately predict future eclipse timings.

Bidirectional Rotating Turbine Hybrid Triboelectric‐Electromagnetic Wave Energy Harvester for Marine Environment Monitoring

AbstractHydrokinetic energy, a vital renewable resource, holds promise for addressing fossil fuel shortages to ensure a sustainable future. This study proposes an efficient and stable ocean wave energy harvesting system that combines a triboelectric nanogenerator (TENG), an electromagnetic generator (EMG) with a planetary gear system, and a driving turbine. The turbine transforms the up‐and‐down motion in water into continuous, unidirectional rotational motion. An EMG device accelerated by a planetary gear system further ensures sustained output at very low frequencies (0.25 Hz) and boosts the upper limit of power generation at medium to high frequencies. Under water wave conditions with a 1 Hz frequency, the TENG component yields an output of up to 2200 V and 122 µA, while the average EMG output is 15 V and 80 mA. Remarkably, the entire system maintains a steady and uninterrupted output even at extremely low frequencies (0.25 Hz). The peak power outputs for the TENG and EMG components are 115 and 350 mW, respectively, with power densities of 32.55 and 329.78 W m−3, surpassing prior achievements. This research demonstrates self‐powered applications and provides an efficient method to amplify water wave forces, enhancing energy harvesting capabilities for practical marine environmental monitoring.

Differences between Stable and Unstable Architectures of Compact Planetary Systems

We present a stability analysis of a large set of simulated planetary systems of three or more planets based on architectures of multiplanet systems discovered by Kepler and K2. We propagated 21,400 simulated planetary systems up to 5 billion orbits of the innermost planet; approximately 13% of these simulations ended in a planet–planet collision within that time span. We examined trends in dynamical stability based on dynamical spacings, orbital period ratios, and mass ratios of nearest-neighbor planets as well as the system-wide planet mass distribution and the spectral fraction describing the system’s short-term evolution. We find that instability is more likely in planetary systems with adjacent planet pairs that have period ratios less than 2 and in systems of greater variance of planet masses. Systems with planet pairs at very small dynamical spacings (less than ∼10–12 mutual Hill radii) are also prone to instabilities, but instabilities also occur at much larger planetary separations. We find that a large spectral fraction (calculated from short integrations) is a reasonable predictor of longer-term dynamical instability; systems that have a large number of Fourier components in their eccentricity vectors are prone to secular chaos and subsequent eccentricity growth and instabilities.

A system mapping activity to visualize lithium’s interconnectedness to societal and environmental aspects of the green energy transition

Abstract Lithium’s role in the global green energy transition provides an engaging context to visualize the interconnectedness of chemistry to seismic shifts taking place in society. Lithium has seen a dramatic increase in utilization, but given lithium’s current low rates of recyclability, this development is exacerbating the e-waste problem. Equally important, we posit that lithium extraction, from either brine or ore, and the associated impacts on the environment and local communities should not be so easily decoupled from the shift in human behaviors causing its demand. Presented here is a mapping activity that was trialed in professional learning workshops organized in New Zealand for secondary/high school chemistry teachers. In their mapping activity response, the teachers were able to connect typical school chemistry content (batteries, chemical processes) with environmental (planetary systems) and social, economic, and ethical considerations (useful products, unintended consequences, inequity in access to water) of the ongoing electrification of society. The teachers indicated a positive intention to utilize the activity, or one similar with a different chemical process or product, in their own classrooms. A school-ready version of the activity is provided in the supplementary information, which was revised based on feedback from the teachers attending the workshops.

Natural Characteristics of a Marine Two-Stage Tandem Hybrid Planetary System

This study focuses on a marine two-stage tandem hybrid planetary system. Natural frequencies and vibration modes are determined using a translational–torsional coupled dynamic model. Based on the motion characteristics of the transmission system, free vibration is categorized into three typical modes. The parameter sensitivity of natural frequencies is computed, and the effects of structural parameters such as unequally spaced planet, mesh stiffness, planet mass and rotational inertia on the natural frequencies are analyzed. Utilizing the coupling factor, the mode transition criterion for the natural frequencies response to parameters is formulated. The results demonstrate that the vibration modes of the two-stage tandem hybrid planetary system can be classified as the fixed-axis train vibration mode, the differential train vibration mode, and the coupled vibration mode. Unequally spaced planet primarily disrupts vibration modes without significantly affecting natural frequencies. In contrast, the effects of mesh stiffness, planet mass and rotational inertia on the modes are opposite to those of unequally spaced planets. The validity of the parameter sensitivity and mode transition criterion is substantiated through illustrative examples.

Dynamical coupling of Keplerian orbits in a hierarchical four-body system: from the Galactic Centre to compact planetary systems

ABSTRACT This study focuses on the long-term evolution of two bodies in nearby initially coplanar orbits around a central dominant body perturbed by a fourth body on a distant Keplerian orbit. Our previous works that considered this setup enforced circular orbits by adding a spherical potential of extended mass, which dampens Kozai–Lidov oscillations; it led to two qualitatively different modes of the evolution of the nearby orbits. In one scenario, their mutual interaction exceeds the effect of differential precession caused by a perturbing body. This results in a long-term coherent evolution, with nearly coplanar orbits experiencing only small oscillations of inclination. We extend the previous work by (i) considering post-Newtonian corrections to the gravity of the central body, either instead of or in addition to the potential of extended mass, (ii) relaxing the requirement of strictly circular orbits, and (iii) removing the strict requirement of complete Kozai–Lidov damping. Thus, we identify the modes of interorbital interaction described for the zero eccentricity case in the more general situation, which allows for its applicability to a much broader range of astrophysical systems than considered initially. In this work, we scale the systems to the orbits of S-stars; we consider the clockwise disc to represent the perturbing body, with post-Newtonian corrections to the gravity of Sagittarius A* playing the role of damping potential. Considering post-Newtonian corrections, even stellar-mass central bodies in compact planetary systems can allow for the coupled evolution of Keplerian orbits.

A survey for radio emission from white dwarfs in the VLA Sky Survey

ABSTRACT Radio emission has been detected from tens of white dwarfs, in particular in accreting systems. Additionally, radio emission has been predicted as a possible outcome of a planetary system around a white dwarf. We searched for 3 GHz radio continuum emission in 846 000 candidate white dwarfs previously identified in Gaia using the Very Large Array Sky Survey (VLASS) Epoch 1 Quick Look Catalogue. We identified 13 candidate white dwarfs with a counterpart in VLASS within 2 arcsec. Five of those were found not to be white dwarfs in follow-up or archival spectroscopy, whereas seven others were found to be chance alignments with a background source in higher resolution optical or radio images. The remaining source, WDJ204259.71+152108.06, is found to be a white dwarf and M-dwarf binary with an orbital period of 4.1 d and long-term stochastic optical variability, as well as luminous radio and X-ray emission. For this binary, we find no direct evidence of a background contaminant, and a chance alignment probability of only ≈2 per cent. However, other evidence points to the possibility of an unfortunate chance alignment with a background radio and X-ray emitting quasar, including an unusually poor Gaia DR3 astrometric solution for this source. With at most one possible radio emitting white dwarf found, we conclude that strong (≳1–3 mJy) radio emission from white dwarfs in the 3 GHz band is virtually non-existent outside of interacting binaries.