Solar System Research最新文献

Using numerical experiments, an analysis was made of the influence of changes in the shape of the asteroid on the magnitude of disturbances occurring in its rotational motion during close approach to the Earth. The influence of perturbations in the rotation of an asteroid (changes in the period and orientation of the rotation axis) on the orbital dynamics is considered by changing the magnitude of the Yarkovsky effect. It has been established that during tidal deformation of the asteroid’s figure due to its approach to the Earth, accompanied by a change in the moments of inertia, the magnitude of the perturbations in rotation is significantly higher than in the case of an unchanged figure. It has been shown that a 10–25% change in the inertial parameters of the asteroid (99 942) Apophis during its approach to the Earth in 2029 leads to a 2–4-fold increase in the size of the regions in which the rotation period and the angle characterizing the inclination of the rotation axis to the orbital plane can change. Perturbations in the rotation of the asteroid lead to a change in the parameter A₂, characterizing the Yarkovsky effect. The size of the region of change of parameter A₂ in the presence of deformations in the asteroid’s figure also increases significantly compared to the case of an unchanged figure.

Since 1969, the Lunar Laser Ranging (LLR) technique has been used to build and improve the ephemeris of the Moon. The results of processing of new laser observations are considered here to determine more accurately the lunar ephemeris parameters for the Ephemeris of Planets and the Moon (version EPM2023a), which was created and is maintained by the Institute of Applied Astronomy of the Russian Academy of Sciences. In 2014, the development of a new version of the EPM (including the Moon) started within the upgraded ERA-8 system (where ERA stands for Ephemeris Research in Astronomy). The new version of the lunar ephemeris implements a model of the orbital–rotational motion of the Moon that is similar to that used in the DE430 version of the NASA JPL Development Ephemerides. In this model, the Moon is considered as an elastic body with a rotating liquid core, and the rotation of the Moon around its center of mass in the celestial coordinate system is described by three Euler angles. Together with new geophysical and geodynamic parameters required today, this model replaced the model proposed by G.A. Krasinsky in the ERA-7 system. In this paper, to obtain the lunar ephemeris parameters for the EPM2023a, we use 33 602 Lunar Laser Ranging observations (LLRos; i.e., normal points), including 1985 new observations. About 100 lunar ephemeris parameters of the EPM2023a were improved, and some of them were compared to the corresponding parameters of the INPOP21a (where INPOP stands for Integration Numerique Planetaire de l’Observatoire de Paris) and DE440 ephemerides. For current projects and practical work in space research, it is necessary to use the latest lunar ephemerides—EPM2022a and EPM2023a.

The paper studies the consequences of probable encounters of interstellar objects of planetary mass (free-floating exoplanets) with the Solar System. As a result of such approaches, mean motion resonances may arise in the dynamics of planets, but entering into the resonances is possible only with selected values of the mass of the interstellar object and the initial conditions of its motion. The most significant resonances that can arise as a result of the approaches have been identified.

The paper considers the problem of modeling the gravitational field of contact binary trans-Neptunian asteroid (486 958) Arrokoth. A so-called gravitating dumbbell is being built—a model of a celestial body that is a pair of gravitating spheres, with the centers separated by a fixed distance. The parameters of the dumbbell are determined in two ways. The first method uses the k-means algorithm, which is known from pattern recognition theory. In the second method, it is assumed that the body possesses dynamic symmetry, and the parameters of the dumbbell are found by solving the so-called moment problem that arises. A comparative analysis of the results is performed.

The results of modeling of the escape of the primary atmosphere under the influence of the heat flux from the core for the exoplanet HD 207496b are considered. It is shown that this mechanism of gas envelope loss is not effective enough due to the relatively low equilibrium temperature of the exoplanet, as well as the relatively large mass. Previously, the high efficiency of photoevaporation of a hydrogen–helium atmosphere under the influence of extreme ultraviolet radiation was shown for HD 207496b (Barros et al., 2023). It has been demonstrated that if HD 207496b has a rocky core without a water mantle, surrounded by an envelope of primary composition, then the mass of the atmosphere should be about 0.5% of the mass of the exoplanet, and the gas envelope will be completely lost after about 500 million years. In this case, the initial mass fraction of the primary atmosphere for HD 207496b should have been about 2.2% (the age of the exoplanet is about 520 million years). However, the escape mechanism driven by the core’s heat flow cannot lead to significant atmospheric loss in this case. At the same time, the obtained result strongly depends on the equilibrium temperature and mass of the exoplanet. Accordingly, HD 207496b may be quite close to the boundary where the influence of core heat flow on gas envelope evolution becomes significant, and the obtained result becomes model-dependent. In this regard, it is advisable in future studies to consider several additional factors: the possibility of a water mantle, radiogenic heat flow, and tidal effects.

The orbiting and positioning of probes in deep-space exploration missions cannot be separated from the support of a software platform for precise orbit determination. The development of a software platform is essential in engineering and scientific applications. Thus, the Wuhan University planetary geodesy group has independently developed a software platform, called Small Body and planets Precise Orbit Determination Toolkit (SPOT), in response to the demand for spacecraft precise orbit determination. Moreover, aligned with the goal of supporting China’s first asteroid exploration mission, this initiative will significantly enhance the country’s scientific contributions in the field of radio science. This paper briefly introduces the design concept, core structure, and main functions of SPOT, and subsequently focuses on some simulation experiments and real tracking data analysis based on SPOT. The functionality and self-consistency of the SPOT were verified through simulation experiments, and construction of some new measurement models and inversions of small body gravity fields. The reliability of the software platform was further verified from the processing of radio tracking data and landmark data from the Rosetta mission, as well as from the Neptunian gravity estimated from the motion of Triton based on astrometric observations. The computational efficiency and accuracy of SPOT have reached international equivalent level.

We describe the plasma–dust system existing near the surface of the Moon and consider the waves and instabilities that can arise in this system in various situations, including when the Moon is inside or outside the Earth’s magnetotail. The mechanism of the charging of dust particles in the near-surface plasma on the Moon is explained. The influence of solar radiation and photoelectrons on the charging of dust particles is noted.

The paper describes the Sun-Terahertz space experiment, planned for 2025–2027 on board the Russian segment of the International Space Station. The goals of the experiment are to obtain data on the Sun’s terahertz radiation, as well as to study solar active regions and solar flares. The scientific equipment of the Sun-Terahertz consists of eight detection channels, which are sensitive to radiation of different frequencies in the range of 0.4–12.0 THz. The purpose of this work is to check the compliance of the actual spectral characteristics of scientific equipment with the calculated ones in the operating frequency range of 0.4–20 THz using auxiliary equipment and the developed methodology.

The ultra-hot Jupiter KELT-9b forces us to reconsider existing models of the upper atmospheres of hot exoplanets, which were previously developed using the example of G or M star systems such as HD209458b and GJ436b. The unique conditions for the interaction of the radiation of an A-class star with the atmosphere necessitate kinetic modeling of excited levels of elements, primarily the hydrogen atom. For KELT-9b, absorption was recorded for several lines of hydrogen and lines of a number of heavy elements, the quantitative interpretation of which is an urgent task. In this work, for the first time, 3D modeling of the atmosphere of a planet with a close location of the Roche lobe has been implemented, taking into account the aeronomy, kinetics of excited hydrogen and several lines of heavy elements.