Magnetic reconnection has recently emerged as an important process in the Martian space environment. In contrast to Earth, Mars lacks a global intrinsic dipole field and possesses an induced magnetosphere shaped by solar-wind interaction with the ionosphere, localized crustal magnetic anomalies, and abundant planetary heavy ions. Recent measurements from Mars Global Surveyor, Mars Express, MAVEN, and Tianwen-1 have revealed reconnection signatures in several distinct regions, including the dayside induced magnetosphere, the induced magnetotail, the crustal-field mini-magnetospheres, and the upper ionosphere. These reconnection signatures include Hall-like magnetic perturbations, multi-species ion outflows, magnetic flux ropes, reconnection fronts, and electron pitch-angle changes indicative of magnetic topology reconfiguration. This review synthesizes recent observational and theoretical progress on Martian magnetic reconnection and discusses its implications for magnetospheric structure, plasma energization, auroral activity, and atmospheric ion escape. Particular attention is given to the effects of interplanetary magnetic field variability, heavy-ion composition, and ionospheric collisionality, which distinguish reconnection at Mars from more familiar terrestrial cases. Although existing observations show that reconnection is a recurrent and potentially important component of Mars–solar-wind coupling, its global occurrence rate, spatial extent, and long-term atmospheric impact remain poorly constrained. Future coordinated multi-spacecraft measurements and multi-scale simulations will be critical for linking local reconnection physics to global plasma transport and atmospheric evolution.
The influence of the zonal harmonics J4 on the positions and stability of the out-of-plane equilibrium points of an infinitesimal mass, in the framework of the photogravitational elliptic restricted three-body problem (ER3BP), has been investigated. The positions change with an increase in the oblateness up to zonal harmonics J4, radiation pressure, eccentricity and semi-major axis of the orbit. The positions and stability of the out-of-plane points are affected by the parameters involved. The effect of these parameters on the positions of the out-of-plane equilibrium points is examined numerically both for the binary system 61 CYGNI and for arbitrary values. The results obtained from this study can be applied to different methods of celestial mechanics, with application to the planetary system.
This study presents a quantitative, scenario-based framework for analyzing humanity's potential progression along the Kardashev scale, with emphasis on the transition to Type I (planetary-scale) and Type II (stellar-scale) civilization status. Using humanity as an empirical reference case, we integrate four coupled dimensions of civilizational development: energy utilization, information processing capacity, large-scale construction mass, and population dynamics, modeled through historical data, empirical trends, and physically motivated growth constraints. Energy availability is characterized using global energy production records and insolation statistics for potentially habitable exoplanets, explicitly acknowledging observational biases toward cooler host stars. Information processing growth is constrained by thermodynamic limits and observed trends in global data generation, while construction mass and population evolution are described using exponential and logistic growth models, respectively. These components are combined into a composite Civilization Development Index (CDI), a weighted logarithmic metric designed to track multi-scale civilizational advancement and tested through sensitivity analyses. Under optimistic assumptions of uninterrupted technological growth and absence of civilization-scale catastrophes, the framework suggests that humanity could reach Type I civilization status on the order of the 23rd century, while Type II status represents a substantially longer-term outcome extending into the third millennium or beyond. These timescales should be interpreted as lower bounds, as catastrophic events, sociopolitical constraints, or resource bottlenecks could significantly delay or prevent such transitions. By explicitly delineating assumptions, uncertainties, and physical constraints, this work provides a structured baseline for studies of long-term civilizational trajectories and the factors governing the emergence or absence of advanced technological civilizations.
Abstract Catastrophic earthquakes (EQs) (M ≥ 8) and global ionospheric plasma variations exhibit unexpected planetary orbital periodicities that cannot be explained by known (geo)physical processes. In this study, we identify a robust pre seismic signature in the Total Electron Content (TEC) of the ionosphere that precedes major EQs by up to two months. This finding leads to a novel forecasting method for large magnitude events, providing a significant advance warning window. We propose that the underlying causal triggering mechanism for such correlated phenomena fits-in the scenario of gravitational focusing of galactic dark matter (DM) streams by the solar system bodies. In this framework, Earth based observational tools like the global GPS network can serve a dual role: monitoring terrestrial dynamics and acting as possible sensitive detectors for DM. We demonstrate how continuous GPS recordings can be exploited to project, in real time, the likely timing and location of major seismic events. This interdisciplinary approach provides a novel route to enhance the reliability of catastrophic EQ forecasting. Concurrently, it offers a new method for the direct detection of the dark sector following otherwise unexpected planetary dependencies. While the Axion Quark Nugget (AQN) framework provides an interesting basis for these results, the identified precursors remain model-independent.
The linear and nonlinear propagation of dust–acoustic waves in an inhomogeneous dusty plasma with nonthermal electrons and ions is investigated. The effects of electron and ion nonthermality, equilibrium plasma densities, dust charge, and temperature ratio are included. By applying the reductive perturbation method, we derive a damped Korteweg–de Vries equation governing the nonlinear evolution of the dust-acoustic mode. The resulting equation and its analytical solution are examined in detail. The soliton amplitude exhibits a non-monotonic dependence on the nonthermal parameters, attaining a maximum at intermediate values as a result of the competition between nonlinearity and dispersion. The results emphasize the joint influence of plasma inhomogeneity, nonthermal populations, and dust charging on dust–acoustic wave dynamics, and they may be tested against contemporary experimental observations in complex plasmas. In several limiting cases, the present results reduce to previously reported models, and the findings are applicable to both laboratory and space dusty plasma studies.
Seismic activity can impact different layers of the Earth’s atmosphere; however, our understanding of lithosphere-atmosphere-ionosphere coupling mechanism still remains limited and is challenging. Previous studies predominantly feature seismo-ionospheric changes associated with large earthquakes/tsunamis. Seismic-induced changes in the Mesosphere-Lower Thermosphere (MLT) region have not been properly addressed and are limited to a few reports. We present, here, rare observations of anomalies in the temperature and airglow of the MLT region using Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on board Thermosphere Ionosphere Mesosphere Energetics Dynamics (TIMED) spacecraft measurements for 2025 Mw 8.8 Kamchatka Peninsula Earthquake. Beginning with the Mainshock at 23:24:52 UT on 29 July 2025, over a hundred aftershocks (with a majority exceeding intensity-scale of Mw 5.0) occurred near Petropavlovsk-Kamchatsky and Severo-Kuril’sk in Russia and activity continued beyond 31 July. We found an increase in temperature in the 73–83 km range on 30 July. However, the temperature decreased in the 87–97 km range on 30 and 31 July. Further, we noted a minor increase and distinct decrease in the volume emission rate of OH airglow on 30 July over the height range of 76–82 km and 83–90 km, respectively. Comparatively, significant decrease in OH airglow was seen on 31 July in the 81–96 km height range. Unusual gravity wave (GW) activity was, also, noted with predominant presence of waves with vertical wavelength of 18 km. Similar anomalous temperature enhancement and pronounced decrease in OH airglow was seen during the 2011 Mw 9.1 Tohoku-Oki earthquake as well.
In this work, we aim to advance the Universal Rotation Curve (URC) paradigm by leveraging new data and extending its observational domain. Building on previous studies that established the URC using optical rotation curves reaching the galaxy optical radius R_opt, we exploit the SPARC sample's extended HI rotation curves to construct the URC out to 2R_opt. This crucial extension enables us to investigate the mass distribution of spiral galaxies in a region dominated by dark matter an important step to better constrain galaxy mass models and to explore the nature of the dark matter particle. We find that the URC constructed from the SPARC sample's extended HI rotation curves maintains its universal character out to 2R_opt, with the double-normalized rotation curves collapsing onto a single profile. This extended URC provides new insights into the interplay between baryonic matter and dark matter in shaping galaxy rotation curves, particularly in the outer regions where dark matter dominates. Our results not only reinforce the URC paradigm but also refine our understanding of the mass distribution in spiral galaxies, offering new constraints on galaxy mass models and implications for the nature of dark matter.
Osmium is a third-peak neutron-capture element predominantly produced by the rapid (r-) process, and it is a valuable tracer of early Galactic chemical enrichment. However, osmium abundance measurements in Galactic stars remain limited due to observational challenges. We present new osmium abundances for 23 stars at intermediate metallicities (−2.5≤ [Fe/H] ≤−1.0) within the framework of the MINCE (Measuring at Intermediate Metallicity Neutron-Capture Elements) project. A standard abundance analysis was carried out using one-dimensional LTE model atmospheres and the optical Os I line at 479 nm observed in high-quality UVES spectra. The derived [Os/Fe] ratio exhibits an anticorrelation with [Fe/H], supporting efficient r-process enrichment during the early phases of the Milky Way’s evolution. We also investigated Os abundances across different Galactic components, finding that halo and Gaia–Sausage–Enceladus stars are more Os-rich than thick-disk stars. A comparison between Os and europium abundances supports a common r-process origin for these elements at intermediate metallicities.
The neutron capture cross section of 64Ni is an important parameter in nuclear astrophysics that is needed to accurately simulate stellar nucleosynthesis and validate stellar models. 64Ni is among the seeds of the s-process and its capture cross section has been found to have an important effect on the predicted abundances of many nuclei synthesized in Asymptotic Giant Branch (AGB) and massive stars. Despite its relevance, the measurements of the 64Ni(n,γ) available in the literature are scarce and discrepant. For this reason, a new accurate time-of-flight measurement has been performed at the n_TOF facility at CERN, taking advantage of its high instantaneous neutron flux, and using a highly enriched 64Ni sample. The first preliminary results show important discrepancies with respect to the cross sections recommended in the most recent releases of the evaluated nuclear data libraries. In particular, a large resonance reported at 9.52 keV is not observed. As a consequence, a significant reduction in the Maxwellian-Averaged Cross Section (MACS) obtained from evaluated data libraries in the 5–25 keV thermal energy region is expected.
We present the results of the analysis of nine polarization and micro-variability observations of BL Lacertae using a turbulent cell model. We perform a similar analysis of a simulated TEMZ light curve generated with the Turbulent Extreme Multi-Zone (TEMZ) model and compare the results. Observations of short-timescale variability of flux and polarization are important to understanding the physical conditions in the blazar jet. We find that the micro-variations exhibited by the BL Lac data analyzed here are well fit by a turbulent cell model consisting of multiple pulses, with an average correlation coefficient of r similar to 0.94. We compare these results with a similar analysis of light and polarization curves from a TEMZ simulation, which employs many more cells with physical properties related across cells following the Kolmogorov spectrum. We find that groups of turbulent cells identified in the TEMZ model by our analysis are similar to the input cell structure of the simulation. We find that the results from the actual BL Lac light curve and polarization curves match very well with the results from analyzing the TEMZ simulated light curves. We find no apparent trend or direct correlation between the cells determined from the flux curves and polarization degree, or polarization angle in either the BL Lac or the TEMZ data sets.
Molybdenum (Mo, Z = 42) is a neutron-capture element with seven stable isotopes that can be produced by different processes. Previous studies have shown a large scatter in molybdenum abundances for metal-poor ([Fe/H] < −1) stars, indicating that multiple nucleosynthetic channels are responsible for molybdenum production even at very low metallicity. To understand which different nucleosynthesis processes are involved in the chemical enrichment of this element in the Galaxy, a large sample of precise molybdenum abundance is required. In this study, we present molybdenum abundances of 27 metal-poor stars from the Measuring at Intermediate Metallicity Neutron-Capture Elements project sample. We derived molybdenum abundances using three Mo i lines at 550.6 nm, 557.0 nm, and 603.0 nm, which proved to be reliable for measuring Mo abundances in giant stars with [Fe/H] >−2. Our derived [Mo/Fe] abundance ratios show on average slightly higher values (∼0.2 dex) compared to the literature samples. This may be due to an observational bias or to non-local thermodynamic equilibrium effects. We also found that Gaia-Sausage-Enceladus candidate stars have lower [Mo/Fe] than the sample average, while the only Sequoia candidate star has a higher [Mo/Fe] than most sample stars.
About half the elements heavier than iron in the universe, like silver and gold, are created in the rapid neutron-capture (r-)process. However, today, almost 70 years after the theoretical prediction of this process, it is still highly debated in what type of stellar explosions it can take place. One of the best places to search for answers is in ancient, metal-poor stars formed from the enriched gas. Their chemical makeup is like a time capsule, a direct fingerprint of the elements produced by the stellar generations that came before them. Since the first highly r-process-enhanced star, CS 22892-052 was discovered more than 30 years ago, multiple projects like the Hamburg/ESO r-Process Enhanced Star (HERES) survey, the Chemical Evolution of r-process Elements in Stars (CERES) project, and the r-Process Alliance (RPA) have searched for more r-process-enriched stars in the Milky Way. At the same time, numerous r-process-enriched stars have been discovered in stellar streams and dwarf galaxies. Here we present an overview of recent advances in finding r-process-enriched metal-poor stars and what the detailed chemo-dynamical analysis of these stars can tell us about heavy element nucleosynthesis and the astrophysical site(s) of the r-process.
This technical note evaluates the observational performance limits of unguided smartphone-based astrophotography using a large-aperture Newtonian telescope under low-latitude sky conditions. Observations were conducted with a consumer-grade 10-inch Newtonian reflector coupled to an iPhone 15 Pro Max mounted on a manual altazimuth system, without motorized tracking, under semi-urban skies in Planeta Rica, Colombia (8.4° N). Image acquisition employed 5 s exposures in night mode combined with real-time manual drift correction. Under these conditions, resolved stellar and nebular structures were obtained for the Orion Nebula (M42) and the open clusters Messier 44 and Messier 41, reaching a limiting magnitude of approximately 9.5 while maintaining stellar elongation below ~1–1.3 arcminutes, consistent with the expected sidereal drift during a 5 s exposure. Lunar imaging achieved high spatial fidelity, resolving terminator features such as Tycho and Mare Imbrium with negligible motion artifacts. Imaging of Sirius (–1.46 mag) revealed pronounced sensor saturation and blooming, highlighting dynamic range limitations inherent to smartphone detectors. Quantitative analysis indicates that active manual correction reduced positional drift by approximately 52% relative to theoretical unguided motion models. The results demonstrate that optimized acquisition protocols enable reproducible and methodologically interpretable imaging of bright astronomical targets at equatorial latitudes, providing a practical framework for characterizing the constraints of unguided smartphone astrophotography.
The two most severe cosmological tensions in the Hubble constant \( H_0 \) and the matter clustering amplitude \( S_8 \) have the same relative discrepancy of 8.3%, which suggests that they may have a common origin. Modifications of gravity and exotic dark fields with numerous free parameters introduced in the Einstein field equations often struggle to simultaneously alleviate both tensions; thus, we need to look for a common cause within the standard \( \Lambda \)CDM framework. At the same time, linear perturbation analyses of matter in the expanding \( \Lambda \)CDM universe have always neglected the impact of comoving peculiar velocities \( \mathbf{v} \) (generally thought to be a second-order effect), the same velocities that in physical space cannot be fully accounted for in the observed late-time universe when the cosmic distance ladder is used to determine the local value of \( H_0 \). We have reworked the linear density perturbation equations in the conformal Newtonian gauge (sub-horizon limit) by introducing an additional drag force per unit mass \( -\Gamma(t)\mathbf{v} \) in the Euler equation with \( \Gamma \equiv \gamma(2 H) \), where \( \gamma\ll1 \) is a positive dimensionless constant and \( 2H(t) \) is the time-dependent Hubble friction. We find that a damping parameter of \( \gamma = 0.083 \) is sufficient to resolve the \( S_8 \) tension by suppressing the growth of structure at low redshifts, starting at \( z_\star\simeq 3.5-6.5 \) to achieve \( S_8\simeq 0.78-0.76 \), respectively. Furthermore, we argue that the physical source causing this additional friction (a tidal field generated by nonlinear structures in the late-time universe) is also responsible for a systematic error in the local determinations of \( H_0 \): the inability to subtract peculiar tidal velocities along the lines of sight when determining the Hubble flow via the cosmic distance ladder. Finally, the dual action of the tidal field on the expanding background—reducing both the matter and the dark-energy sources of the squared Hubble rate \( H^2 \), thereby holding back the cosmic acceleration \( \ddot a \)—is of fundamental importance in resolving cosmological tensions and can also substantially alleviate the density coincidence problem.
Supergiants are luminous post-main-sequence massive stars whose effective temperatures (Teff) are key inputs for stellar evolution and feedback studies. We present a photometry-based procedure to derive Teff for a sample of galactic supergiants of spectral types B and A by fitting the spectral energy distributions (SEDs) in the UV-to-mid-IR range to ATLAS9 model spectra converted into synthetic photometry using the corresponding passband transmission profiles while simultaneously solving for the line-of-sight extinction. The SEDs were constructed from published data taken in different photometric systems (Johnson or Kron–Cousins UBVRI, Strömgren uvby, JHK magnitudes from various sources, and AllWISE) and supplemented with UV TD-1 fluxes for brighter stars. The interstellar extinction law is based on Cardelli, Clayton & Mathis approximation assuming a total-to-selective ratio RV=AV/E(B−V)=3.1. The best-fitting parameters are obtained by minimizing a covariance-weighted χ2 statistic in logarithmic flux space over a grid of AV values and a discrete model grid. We test the method on 20 targets and find generally good agreement with published literature temperature estimates. The main limitations are non-simultaneous photometry for possibly variable objects and the residual coupling between temperature and reddening in broadband SED fitting. This study is intended as a methodological demonstration on a pilot sample rather than a definitive parameter catalog.
Annual parallaxes of Galactic long period variable stars (LPVs) are essential for determining their distances and intrinsic properties, but their measurement remains challenging because of their large stellar sizes, circumstellar matter, and time-variable surface brightness asymmetry. In this study, we compare astrometric measurements obtained from very long baseline interferometry (VLBI) and Gaia Data Release 3 (DR3) for 43 Galactic LPVs. The parallaxes from the two methods are generally consistent within uncertainties for about half of the sample, although Gaia DR3 parallaxes tend to be slightly smaller than the VLBI values. This is consistent with previously reported systematic offsets. The behavior of parallax uncertainties differs between the two techniques: VLBI parallax errors increase with increasing parallax, whereas Gaia DR3 errors remain nearly constant. Consequently, VLBI measurements are more effective for LPVs with parallaxes smaller than approximately 2 mas, corresponding to distances beyond 500 pc. Proper motions are also compared, showing general agreement with a 2-sigma dispersion of approximately 13 km s−1, consistent with typical AGB outflow velocities. These results demonstrate the complementarity between VLBI and Gaia astrometry. We also find that the dispersion of parallax residuals becomes slightly larger for sources with pulsation periods around one year, suggesting a coupling of timescales between the stellar pulsation and the annual parallax.
We present new high-dispersion optical spectra of the planetary nebula NGC 2371 obtained with the Manchester Echelle Spectrometer at the OAN-SPM 2.1 m telescope, complemented with 3D morpho-kinematic modelling using ShapeX. The data reveal that the present-day morphology of NGC 2371 is the outcome of multiple episodic mass-loss events rather than a single outflow. Our best-fitting model simultaneously reproduces the direct images and the Position–Velocity (PV) diagrams, and consists of a barrel-shaped shell with younger polar caps, extended bipolar lobes, and a pair of misaligned low-excitation [N ii] knots interpreted as jet-like ejections. The derived kinematical ages of the main structures, spanning ≃1600 to ≃4400 yr, indicate successive episodes of mass loss with different geometries and timescales. The nearly perpendicular bipolar lobes, the absence of a pronounced waist, and the surface distortions of the large-scale structures cannot be explained solely by standard axisymmetric wind interactions. Instead, our results point to a combination of shaping agents, including a late thermal pulse (born-again scenario) possibly related to the H-deficient [WR]-type nature of the central star, binary-driven interactions, and episodic jet activity. NGC 2371 thus provides a particularly instructive case where multiple shaping agents may operate, and where some of the relevant physical processes remain only marginally explored in current models of PN formation and evolution.
Accurate modeling of ion-molecule reaction networks is essential for understanding the chemical evolution of planetary ionospheres, particularly for giant planets where proton-transfer chains drive atmospheric composition. However, predicting reaction rates in these ultracold environments remains a challenge due to the non-trivial interplay between vibrational dynamics and quantum tunneling. In this work, we present a chaos-diagnostic framework that integrates multireference electronic structure theory, Adiabatic Gauge Potentials (AGP), and Random Matrix Theory (RMT) to characterize the microscopic dynamics of proton transport. Using the formation of H_3^+ and the proton-bound cluster H_5^+ as representative model systems relevant to Jovian atmospheres, we demonstrate that the Transition State (TS) acts as a dynamical bottleneck where quantum chaos is notably suppressed ( ⟨ r ⟩≈ 0.36 ), effectively enhancing tunneling probabilities. We introduce a “fragility index” based on the AGP slope to quantify how specific vibrational modes reintroduce chaos and suppress reactivity. This diagnostic approach offers a generalizable, data-driven metric for identifying vibrationally gated pathways in complex astrochemical networks, providing a theoretical basis for refining kinetic models of planetary and interstellar plasmas.
The observed unusual behaviors of the orbits of Trans-Neptunian objects as well as the gravitational anomalies detected by the Optical Gravitational Lensing Experiment can be explained by assuming the existence of a ninth planet in the Solar System, having a mass of the order of , and located at the distance of 300–1000 AU from the Sun. However, since no optical counterpart of Planet 9 was observed, it is reasonable to assume that it must have a very low luminosity. In this context various proposals on the nature of Planet 9 have been been advanced, including the possibility that it is a black hole, an axion or a dark matter star. In the present study we propose that dark matter heating of Planet 9 could generate a thermal radio flux that could allow its observational detection, even if Planet 9 is a very dark object. As a first step in this study we estimate the dark matter impact parameter, the mass and the kinetic energy deposition rates, as well as the surface temperature of Planet 9. By adopting a specific model for the time evolution of the planet, under the assumption of a long time capture of dark matter, the surface temperature of Planet 9, and the spectral features of the emitted radiation are obtained. Our results indicate that dark matter capture may provide an efficient mechanism for the heating of Planet 9, and also provide a specific observational signature of the planet. The numerical evaluations depend on the unknown value of the dark matter-ordinary matter interaction cross-section, with the estimates obtained as a function of its ratio and the saturation cross section for dark matter to deposit its entire energy. For a value of this ratio of 10^-10 , and for a dark matter density of the order of 1.32× 10^-17 g/cm3, in around Gyr the surface temperature of Planet 9 can reach values of the order of 200 K, or even higher, with a maximum wavelength of around λ _max=1.44× 10^-3 cm, situated in the infrared domain.
We present a theoretical model to investigate the nonlinear behavior of gravito-electrostatic fluctuations in an unmagnetized self-gravitating visco-elastic dusty plasma of infinite extension. It is composed of five distinct species: nonthermal lighter (inertialess) components–electrons, positive ions, and negative ions–and thermal heavier (inertial) components–neutral and charged dust grains. Applying nonlinear normal mode analysis, we derive a unique pair of extended Korteweg–de Vries–Burgers (KdV–B) equations that describe the hybridized dynamics of coupled gravito-electrostatic potential fluctuations. A judicious numerical platform is constructed to understand the exact nature of the fluctuation dynamics. It is reviewed that the KdV-B system manifests as electrostatic narrow solitary spectral patterns and the corresponding self-gravitational broad counterparts. The steady-state nature of the fluctuation dynamics is found to be sensitively dependent on diverse plasma parameters. Astronomical applicability of the investigated results in light of current observational missions is finally outlined.
