Solar System Research最新文献

In 2023–2024, astrometric and photometric observations of the potentially hazardous asteroid 139622 (2001 QQ142) were carried out using telescopes of the Main Astronomical Observatory of the Russian Academy of Sciences. A series of astrometric observations of the asteroid positions have been obtained, which have a root-mean-square accuracy of one observation for ZA-320M σ = ±0″.21 and for MTM-500M σ = ±0″.07. The evolution of its orbit and the circumstances of its close approaches to Earth were studied, and the influence of nongravitational effects on its motion was estimated. Based on photometric observations of the asteroid in the integral bands of the telescopes, a light curve was constructed, and its axial rotation period was refined: P = 17.0232 ± 0.0040 h.

The paper presents the results of processing of positional observations of Jupiter, Saturn, Uranus, Neptune, and their satellites, as well as Pluto, carried out at the Pulkovo Observatory, as well as at the Mountain Astronomical Station of the Central Astronomical Observatory of the Russian Academy of Sciences (MAS CAO RAS) and at the Abastumani Astrophysical Observatory from the beginning of the 20th century to 2018. The observations were taken from the database of the Central Astronomical Observatory of the Russian Academy of Sciences, with the exception of two groups of observations taken from the VizieR database. The processing was carried out using the planetary ephemerides EPM developed at the Institute of Applied Astronomy of the Russian Academy of Sciences, as well as the ephemerides of the Galilean satellites and Neptune’s satellites and analytical theories of the satellites of Saturn and Uranus. During the processing, corrections were taken into account when switching from older star catalogs to modern ones, to which the observations were reduced. The results of a comparative analysis of the accuracy of determining planetary orbits using Pulkovo observations and without them are presented.

In the framework of nonextensive statistical mechanics of Kaniadakis, the integral stability theorem of Chandrasekhar has been generalized for a spherically symmetric distribution of matter and blackbody radiation in a protoplanetary cloud being in a state of gravitational equilibrium. For this purpose, we use the elements of deformed thermodynamics for an ideal gas, the deformed canonical Gibbs distribution, as well as the effective gravitational constant evaluated within the Verlinde formalisms. In the κ-statistics context, the modified thermodynamic properties of blackbody radiation, specifically, the analog of Stefan’s law for the radiation energy and the generalized expressions for the entropy, heat capacity, and radiation pressure, have been obtained. The proposed method of combining the mentioned anomalous physical processes provides an alternative to the classical procedure of Chandrasekhar’s derivation of the well-known integral theorems for gaseous configurations being in gravitational equilibrium. These results are to be used in modeling the processes of joint formation and evolution of protostars and an exoplanetary cloud from a single nebula.

In the framework of nonextensive Tsallis statistics, we derive the Jeans gravitational instability criteria for a self-gravitating protoplanetary disk, the matter of which consists of a mixture of a conducting ideal q-gas and modified radiation of a photon gas. The instability criteria are derived from the corresponding dispersion relations written for both neutral matter of the disk and magnetized plasma with modified blackbody radiation. We construct the thermodynamics of a photon gas based on the nonextensive Tsallis quantum entropy that depends on the deformation parameter. It has been shown that the blackbody q-radiation can stabilize the state of a nonextensive medium of a purely gaseous disk, while for an electrically conducting disk, the Jeans instability criterion is modified by the magnetic field and radiation pressure only in the transverse mode of propagation of a perturbation wave.

In this paper, we discuss the construction of nonextensive relativistic dissipative hydrodynamics of identical particles on the basis of the relativistic kinetic equation obtained earlier in the q-nonextensive context of the Tsallis statistics with taking into account correlation effects (by rejecting the standard hypothesis on molecular chaos) in the collision term. It has been shown that a local collisional equilibrium is described by a generalized version of the relativistic Jüttner distribution. With this distribution, all thermodynamic parameters of state are defined in an explicit form. Linear constitutive relations and transport coefficients, such as shear viscosity, bulk viscosity, and heat conductivity, are derived from the linearized collision integral written in the Anderson−Witting form and evaluated with the relaxation time approximation. The constructed nonextensive relativistic hydrodynamics is to model a wide range of phenomena in astrophysics, cosmology, and high-energy physics.

In the framework of entropic cosmology and Prigogine’s gravitational theory on the link between geometry and matter, providing the production of particles in the cosmological fluid, as well as under the assumption of exchange entropy at the event horizon, a one-liquid model of the evolution of a spatially flat, homogeneous, and isotropic Universe has been developed. To construct it, the energy conservation equation was derived from the first law of thermodynamics by accounting for the gravitationally-induced creation of matter and the exchange energy processes on the apparent horizon of the Universe. On the basis of this equation and the fundamental Friedmann equation describing the expansion of the Universe, as well as in the entropic formalism context, we constructed the modified Friedmann–Robertson–Walker equations that can be used to study various dynamical aspects of the evolution of the Universe with adiabatic creation of matter. When deriving them, we used several forms of exchangeable phenomenological entropies associated with the region of the apparent cosmological horizon.

In the context of the problem of mathematical modeling of the processes of formation of protoplanetesimals in the Solar protoplanetary disk, taking into account fractal concepts about the properties of dispersed dust aggregates in the disk medium, in the paper, on the basis of the parametric Rényi entropy, statistical thermodynamics for nonextensive fractal systems has been constructed and its properties have been determined. It has been established that between the Rényi thermodynamics of nonextensive systems, on the one hand, and the technique of obtaining fractal and multifractal dimensions, based on geometry and stochastics, on the other hand, there is a close relationship. It has been shown that the time evolution of a closed thermodynamic systems to the equilibrium state depends on the sign of the deformation parameter, which is a measure of the nonextensiveness of the fractal system. Various options for constructing fractal dimensions of different orders for fractals and multifractals were discussed and their features have been analyzed. The developed approach allows, from a unified position based on generalized hydrodynamics with fractional derivatives and thermodynamics for fractal media, to model the evolution of cosmological and cosmogonic objects from galaxies and gas-dust astrophysical disks to cosmic dust, a specific feature of which is the remoteness and globality of force interactions between elements of the system, the hierarchy (usually multifractality) of geometric and phase spaces, a large range of spatio-temporal correlations, as well as the presence of asymptotically power statistical distributions.

Within the framework of the nonextensive Kaniadakis statistics based on parametric kappa-entropy, it has been shown how to obtain deformed thermodynamics of complex anomalous systems and determine its properties. The main mathematical properties of the κ-logarithm and κ-exponent, as well as other related functions arising in the development of the Kaniadakis statistical mechanics, have been presented. As a result, a generalization has been obtained for the nonextensive case of the zero law of thermodynamics for two independent subsystems in thermal contact and the so-called physical temperature has been introduced, which is different from the inversion of the Lagrange multiplier (beta ). With the involvement of the generalized first law of thermodynamics and the Legendre transformation and on the basis of the introduced Clausius entropy, new thermodynamic relations have been obtained, which differ from the relations previously derived by the traditional method for nonextensive statistics, which are unsatisfactory from the point of view of macroscopic thermodynamics. Based on the convexity property of the Bergman divergence, spontaneous transitions between stationary states of a complex (kappa )-system have been studied and the Gibbs theorem and the Boltzmann H-theorem have been proven.

A logical scheme of presentation of principles of nonadditive (nonextensive) statistics and thermodynamics has been given, based on parametric definition of Tsallis entropy. The principle of maximum entropy was used to find probability equilibrium (q)-distributions, which at large deviations of a random variable from the mean value have power asymptotics corresponding to empirically established regularities for a wide class of objects to which classical statistical mechanics is not applicable. Consequences of non-normalized Curado–Tsallis averaging of microscopic physical quantities in Tsallis statistics and its formal and practical significance for modeling dynamic (q)-systems, which has recently been presented in large quantities in the literature, have been analyzed. Based on Rathie–Kannappan difference information, spontaneous transitions between system states and a generalized H-theorem have been considered.

The properties of the family of generalized entropies defined by the Sharma–Mittal measure have been investigated. This family includes the Tsallis entropy, the Rényi entropy, the Landsberg–Vedral entropy, the Gaussian entropy, and the classical Boltzmann–Gibbs–Shannon entropy. A two-parameter thermodynamics of nonextensive systems has been constructed on the basis of the Sharma–Mittal statistics and its relationship with generalized one-parameter thermodynamics based on the indicated deformed entropies of the family has been shown. A generalization of the zeroth law of thermodynamics for two independent nonextensive systems in thermal contact has been obtained, introducing into consideration the so-called physical temperature, which differs from the inversion of the Lagrange multiplier (beta ). Based on this and taking into account the generalized first law of thermodynamics and the Legendre transformation, a redefinition of the thermodynamic relationships obtained within the framework of the Sharma–Mittal statistics has been given. Finally, based on the two-parameter information of the Sharma–Mittal difference, the Gibbs theorem and the H‑theorem on the change of these measures during evolution over time have been formulated and proven.