Volume 30, Issue 1

We here-in demonstrate that the proposed hitherto unknown gravitomagnetic dark-force that hypothetically explains the Flat Rotation Curves of Spiral Galaxies — this same force, explains very well, the logarithmic and as-well, the barred spiral shapes of spiral galaxies. That is, much in line with Edward Arthur Milne (1896-1950)’s 1946 ideas — albeit , on a radically and asymptotically different philosophical train of thought, the galactic disk is here assumed to be in a state of free-fall around the central bulge with the hypothetical gravitomagnetic dark-force being the dominant force determining all gravity-related dynamics of the disk, thus leading to logarithmic and barred spiral orbits, hence the shape of spiral galaxies.

During the 40-year photographic period of astronomical observations, the Baldone Astrophysical Observatory has accumulated more than 22,000 direct and 2,500 spectral images. In 2018, the digitization of direct astrophoto images with a resolution of 1200 dpi was completed. A processing methodology for obtaining the equatorial coordinates and photometric characteristics of the objects recorded in digitized astronegatives using the LINUX/MIDAS/ROMAFOT environment has been developed at the Main Astronomical Observatory of the National Academy of Sciences of Ukraine. Program package with success already works in seven observatories. A description of the operation of this program complex in stages and analysis of the obtained results is given. The steps describe the astrometric and photometric reduction process of digital records, as well as the reduction of the obtained instrumental magnitudes to the Johnson UBVR photometric system. The methodology of characteristic curve construction in the case of one exposure is described in detail. From all digitized astrophotoplates to date Approximately 2200 V film negatives, 300 U plates and several R, B plates were processed. As a result, catalogs of the positions and magnitudes of Pluto, 1848 asteroids and comets were obtained. 31 new positions were recorded in the VizieR Pluto catalog VI/155. It was found that the root-mean-square errors of the reduction of the measured coordinates to the equatorial coordinate system of the Tycho-2 catalog have values σ RA , DEC = 0.1-0.2”, and the root-mean-square errors of the reduction of instrumental photometric quantities m to the Johnson system of stellar UBVR-values are also in within σ UBVR = 0.1 − 0.2 m .

Traditional atmospheric models are based on the analysis and fitting of various factors influencing the space atmosphere density. Neural network models do not specifically analyze the polynomials of each influencing factor in the atmospheric model, but use large data sets for network construction. Two traditional atmospheric model algorithms are analyzed, the main factors affecting the atmospheric model are identified, and an atmospheric model based on neural networks containing various influencing factors is proposed. According to the simulation error, the Levenberg-Marquardt algorithm is used to iteratively realize the rapid network weight correction, and the optimal neural network atmospheric model is obtained. The space atmosphere is simulated and calculated with an atmospheric model based on neural networks, and its average error rate is lower than that of traditional atmospheric models such as the DTM2013 model and the MSIS00 model. At the same time, the calculation complexity of the atmospheric model based on the neural networks is significantly simplified than that of the traditional atmospheric model.

New CCD photometric observations and their investigation of the W UMa-type binary, V870 Ara, are presented. Light curves of the system were taken through BVI filters from the Congarinni Observatory in Australia. The new ephemeris is calculated based on seven new determined minimum times, together with the TESS data and others compiled from the literature. Photometric solutions determined by the Wilson-Devinney (W-D) code are combined with the Monte Carlo simulation to determine the adjustable parameters’ uncertainties. These solutions suggest that V870 Ara is a contact binary system with a mass ratio of 0.082, a fillout factor of 96±4 percent, and an inclination of 73.60±0.64 degrees. The absolute parameters of V870 Ara were determined by combining the Gaia EDR3 parallax and photometric elements.

Kaba meteorite as a reference material (one of a least metamorphosed and most primitive carbonaceous chondrites fell on Earth) was chosen for this study providing an adequate background for study of the protoplanetary disk or even the crystallization processes of the Early Solar System. Its olivine minerals (forsterite and fayalite) and their Mg/Fe ratio can help us to understand more about the planet formation mechanism and whether or not the metallic constitutes of the disk could be precursors for the type of planets in the Solar System. A multiple methodological approach such as a combination of the scanning electron microscope, optical microscope, Raman spectroscopy and electron microprobe of the olivine grains give the Fe/Mg ratio database. The analyses above confirmed that planet formation in the protoplanetary disk is driven by the mineralogical precursors of the crystallization process. On the other hand, four nebulae mentioned in this study provide the astronomical data confirming that the planet formation in the protoplanetary disk is dominated or even driven by the metallic constituents.

We consider the problem of building the relationship of high-energy electron flux between Geostationary Earth Orbit (GEO) and Medium Earth Orbit (MEO). A time-series decomposition technique is first applied to the original data, resulting in trend and detrended part for both GEO and MEO data. Then we predict MEO trend with GEO data using three machine learning models: Linear Regression (LR), Random Forest (RF), and Multi-Layer Perceptron (MLP). Experiment shows that RF gains best performance in all scenarios. Feature extraction analysis demonstrates that the inclusion of lagged features and (possible) ahead features is substantially helpful to the prediction. At last, an application of imputing missing values for MEO data is presented, in which RF model with selected features is used to handle the trend part while a moving block method is for the detrended part.

For low Earth orbit (LEO) satellites, solar panel is a firstly key device to convert the solar radiation into the electric power to supply the energy consume. However, the solar array is always suffering from the power degradation due to the harsh space environments. To meet the power balance in the end life of the spacecraft, attitude determination and control system (ADCS) plays an important role in the solar panel direction to change the solar energy input. Here, the solar cell performance parameters from an LEO satellite running on a dawn-dusk Sun synchronous orbit (SSO) are investigated. A yaw maneuver application is presented to satisfy the electric power supply (EPS) risk of the solar cell current decrease. Validated in the space operation, the results have shown that in the yaw mode, the EPS output is improved and the solar cell current is averagely enhanced more than 10% when the orbit incidence is 35°. The yaw maneuver is applied to the state of health (SOH) management with a better power supply. The solution can be widely and usefully taken into account to increase the solar array output for a near-Earth satellite in the risk of the power shortage.

A new method of orbit determination (OD) is proposed: distribution regression. The paper focuses on the process of using sparse observation data to determine the orbit of the spacecraft without any prior information. The standard regression process is to learn a map from real numbers to real numbers, but the approach put forward in this paper is to map from probability distributions to real-valued responses. According to the new algorithm, the number of orbital elements can be predicted by embedding the probability distribution into the reproducing kernel Hilbert space. While making full use of the edge of big data, it also avoids the problem that the algorithm cannot converge due to improper initial values in precise OD. The simulation experiment proves the effectiveness, robustness, and rapidity of the algorithm in the presence of noise in the measurement data.

Russian Academy of Sciences (RAS) is actively working to solve the problem of preventing Near-Earth Object (NEO) hazard. The article provides the goals and objectives of preventing NEO hazard, as well as ways to achieve them. The described ways of achieving the goal are applied in RAS best. The current state and prospects of the Russian contribution to the prevention of NEO hazard are considered. Statistical data on the dynamics of observation of minor planets by Russian telescopes is presented. The structure of the NEO part of hazardous situations classifier developed by Keldysh Institute of Applied Mathematics (KIAM RAS) and structure of perspective National System Security of space activities in outer space are presented, including the system’s response to event classified as dangerous. The article is accompanied by illustrations of potentially hazardous objects in the sky, made by telescopes of the International Network of Optical Telescopes (ISON), coordinated by the KIAM RAS.

This study discusses the usage of Venus gravity assist in order to choose and reaching any point on Venusian surface. The launch of a spacecraft to Venus during the launch windows of 2029 to 2031 is considered for this purpose. The constraints for the method are the re-entry angle and the maximum possible overload. The primary basis of the proposed strategy is to use the gravitational field of Venus to transfer the spacecraft to an orbit resonant to the Venusian one – with the aim of expanding accessible landing areas. Results of the current research show that this strategy provides an essential increase in accessible landing areas and, moreover, may provide an access to any point on the surface of Venus with a small increase in ∆V required for launch from the Earth and in the flight duration. The comparison with the landing without using gravity assist near planet is also given.

The paper considers the possibility of using thin films based on samarium sulfide, as well as composite systems of metal-oxide semiconductors doped with rare-earth elements, as radiation-resistant sensitive materials for monitoring leaks of rocket fuel components. The data of electrophysical studies of the obtained sensor layers were processed within the framework of the semiconductor Fourier spectroscopy constructed in relation to gas-analytical systems and the nonlinear regression algorithm of selective calibration. The latter solves really the problem of sensors’ selectivity including distinguishing the substances of the same homology such as methane, propane and n-hexane.

In this paper, the mechanisms of star formation and the formation of the equatorial gas and dust disk of protostars are considered. The viscous dynamics of the interstellar matter of gas and dust disks is mainly determined by perturbations of the matter density during gas accretion onto the equilibrium core of the protostar. Using the model of pulsating perturbations of the density of the gas-dust envelope of the protostar and the Navier-Stokes equations, the formulas for the dynamic viscosity of Keplerian and almost Keplerian disks are obtained. It is shown that in the regime of unstable equilibrium of the envelope, accretion of gas onto the core of the protostar begins. In the regime of stable equilibrium, the fragmentation of the gas-dust envelope and the equatorial disk of the protostar occurs. In the ring-shaped fragments of the disk, the process of formation of “embryos” of planets begins and accretion on the “embryos” of the planet also begins.

We present intensity curves of solar flares obtained in the H α hydrogen line and CaII H, CaIR 8542Å lines using multichannel spectrographs of Ondřejov Observatory (Czech Republic) for the period 2000–2012. The general behavior of observed intensity curves is practically the same for all flares and is consistent with temporal variations of X-ray emission. However, our results differ significantly from those obtained by other authors for selected flare stars, for example, AD Leo; EV Lac; YZ CMi. We tried to explain the difference in the behavior of Ca II and H α radiation flux by appearance of a shock wave during a flare and slow heating of the plasma.

We present the PRESTALINE package, a novel tool to simulate and analyse spectra of star forming objects. PRESTALINE allows for a direct comparison of theoretical models with observations and simplifies an analysis of observed spectra. This allows researchers to estimate physical conditions in a studied object and to interpret its chemical composition in a quantitative way. The goal of the project is to set up a consistent framework which would bridge a gap between theoretical studies and observations of star forming regions. In this paper, we present the results of applying PRESTALINE to the test object DR21(OH) and discuss the project general possibilities.

We describe the 10-day radio observations of the gamma-ray pulsar J1836+5925. Observations were carried out in the Pushchino Radio Astronomical Observatory at the frequency of 111 MHz using the Large Phased Array of the Lebedev Physical Institute.

We briefly outline the history of the General Catalogue of Variable Stars (GCVS) and the New Catalogue of Suspected Variable Stars (NSV catalogue). Recently, we have completed a revision of the NSV catalogue. Positional information was checked for all its stars and, in many cases, new photometric data were added. As a result, one third of all NSV stars have been transferred to the GCVS. Having determined equatorial coordinates for variable stars in globular star clusters, we began to add them to the GCVS. Two Name-lists published so far contain more than 1700 variable stars in 36 globular clusters; an additional Name-list (about 900 variable stars in 27 globular clusters) will be published before the end of 2021. We discuss problem cases in the literature and in the Catalogue of Variable Stars in Galactic Globular Clusters revealed during our preparation of the Name-lists. The future of traditional catalogues of variable stars (GCVS; AAVSO Variable-star Data Index VSX) is discussed.

A large number of galaxies have large-scale magnetic fields which are usually measured by the Faraday rotation of radio waves. Their origin is usually connected with the dynamo mechanism which is based on differential rotation of the interstellar medium and alpha-effect characterizing the helicity of the small-scale motions. However, it is necessary to have initial magnetic field which cannot be generated by the dynamo. One of the possible mechanisms is connected with the Biermann battery which acts because of different masses of protons and electrons passing from the central object. They produce circular currents which induce the vertical magnetic field. As for this field we can obtain the integral equation which can be solved by simulated annealing method which is widely used in different branches of mathematics

We analyze the archival XMM-Newton X-ray observations of 15 γ Cas analogue stars and two candidates for such objects. The EPIC spectra of the considered stars in the range of 0.2-8 keV were extracted and fitted by different models. Our estimates show that assuming the X-ray emission from γ Cas analogues to be totally thermal, their model plasma temperatures can reach anomalously high values. However including an additional power components to the model spectra leads to significant decreasing of the plasma temperatures. The spectral index of the power component is about 1.5, and the fraction of this in the total model flux is rather large (50-90%). Moreover, it decreases with expanding temperature of the X-ray emitting plasma as compared to typical OB stars. We conclude that γ Cas analogues can produce nonthermal X-ray emission within the framework of the Chen & White (1991) model, while if the nonthermal X-rays from typical OB stars exists, they should be generated by different processes.

In this paper, we develop an early idea of one of the authors (Nuritdinov 1992a,b), who was the first to propose the mechanism of instability of the warp perturbation mode on the background of a nonstationary disk. For this aim, we have studied a model of a nonlinearly non-stationary self-gravitating disk with an anisotropic velocity diagram. The model has a composite nature, or rather, it is a superposition of isotropic and anisotropic states of the disk. In the general case, it is obtained a nonstationary analogue of the dispersion equation of this composite model. We have also investigated the behavior of the domed perturbation mode, the instability of which leads to the formation of a classical bulge in the central region of the disk. In addition, we considered the critical diagrams of the dependence of the virial ratio on the rotation rate of the system for various values of the superposition parameter and the corresponding diagrams for the increments of instability.

Solar activity (SA) dynamics increases mankind’s evolutionary adaptability to pandemics. Flu pandemics from 1880 to 2020 took place during maximum or minimum of solar cycles. The article discusses several factors that modulated the development of the COVID-19 pandemic: SA dynamic, genetic population features, environment temperature, the effect of lockdowns, and vaccination in various countries. The population genetic composition turned out to be the most significant factor for coronavirus mortalities during a SA global minimum 2019-2020. COVID-19 pandemic is most severe in countries with a dominant haplogroup R1b (the relative number of deaths per million is more than 12-25). Local COVID-19 epidemics were more easily in countries with a dominant haplogroup N (relative number of deaths less than 3). The incidence per million people in haplogroups R1b: R1a: N has a ratio of about 7: 2: 1. This ratio does not depend on the pandemic waves and the population vaccinated rate. Vaccination effectiveness may depend on the population’s genetic characteristics too. It is expected to maintain extremely low solar activity during the 30 years. Under these conditions, a twofold increase in the number of pandemics (every 5-6 years instead of 10-11 years) can be expected with pronounced genogeographic differences.

We determine the interstellar extinction in the selected high-latitude areas of the sky based on Gaia EDR3 astrometry and photometry and spectroscopic data from RAVE survey. We approximate the results with the cosecant law in each area thus deriving the parameters of the barometric formula for different lines of sight. The distribution of the parameters over the entire sky is described using spherical harmonics. As a result, we get a mathematical description of the interstellar visual extinction for different lines of sight and distances from the Sun which can be used for estimating interstellar extinction.

The data of mean magnetic field (MMF) of the Sun obtained at the Wilcox Solar Observatory (Stanford, USA) in 1975–2020 are analysed. It was concluded that the MMF maximum occurs, on average, 1.5–2 years later relative to the maximum of Wolf numbers. To analyze the changes in the MMF, a new method for searching for periodicities has been developed, which takes into account the change in the sign of the magnetic field from cycle to cycle. This method made it possible to find the main synodic periods of rotation of the magnetic field with values of 27 d .021 ± 0 d .008, 26 d .796 ± 0 d .008 and 27 d .260 ± 0 d .008, each of which has two splitting components associated with a change in the polarity of the magnetic field during the transition from one cycle of solar activity to another. The stability of these periodicities for more than 45 years indicates that the Sun as a star looks like a horizontal magnetic dipole (in addition to the observed vertical one), which changes its sign every 11 years and rotates with different periods.

Measurements of velocity and magnetic field in near-Earth heliosphere is analized in order to investigate systematical deflection from transversality of the velocity and magnetic field fluctuations in undisturbed solar wind. Fluctuations occurred in the meridional plain of heliosphere (RN plain of the RTN reference system) are transversal with respect to mean magnetic field during periods of high solar activity, but they become non-transversal close to solar cycle minima. This phenomenon is investigated focusing on a role of Alfvén waves. It is shown that deflections from transversality is mostly expressed by fluctuations in slow solar wind streams with low contribution of Alfvén waves, whereas strongly Alfvénic turbulence undergo such deflection in a less degree. In addition, we consider orientation of velocity fluctuations in the azimuthal (RT) plain of heliosphere, which also indicates some interesting features.

We introduce the application of the clustering algorithm to the preliminary compiled list of probable wide pairs of co-moving stars. The main aim of such development is a possibility of unsupervised blind search of coeval loose stellar structures over significant regions in space. Using Gaia EDR3 data, we investigated the application of the method to nearby region hosting recently discovered loose structures – tidal tails of Coma Ber star cluster and a nearby stellar group named Group X. We compare the results of straightforward clustering of stellar data with results of using our method with varying parameters. We then compare the results of our method to the recent results of the two groups of authors who independently discovered the discussed structures. We find parameters allowing the method to find the full scope of distributed stellar groups without preliminary knowledge of their characteristics. It decreases the risk of false positive clustering and improves the ability to discover loose stellar groups, in comparison with the application of clustering algorithm to the individual stars. Further we obtain a refined dataset of probable members of both stellar groups and independently obtain their ages (700 ± 70 Myr and 450 ± 100 Myr) and space velocities ((U,V,W) = (8.63 ± 0.13, 6.63 ± 0.20, 6.65 ± 0.95) km/s for Coma Ber star cluster, and (U,V,W) = (7.70 ± 0.12, 3.27 ± 0.45, 5.69 ± 0.80) km/s for Group X). Our results are in very good agreement with those of previous investigators.

The possibility of analyzing the line of sight (LOS) velocity and its gradient at each point of the Hinode SOT/SP maps using bisector analysis is revealed. A technique for obtaining such gradient is described. To estimate the velocity gradient, it is necessary to know both the velocity value and the layer height to which the bisector point is responded. We have constructed and tested a method to determine this height. We found velocities at the same heights for lines Fe I λ 6301, 6302 Å averaged over the whole map. It turned out that these velocities have some difference that changes with height and time. The error in the estimating of average velocity for the whole map is 2 m·s −1 . It follows that the wavelengths of lines 6301 and 6302 given in the NIST tables may differ from the real ones at 5.5 mÅ. Or there is an inaccuracy in the spectrograph dispersion specified in the FITS files. As an example, the curves of changes with the height of the LOS velocity and its gradient were constructed both for points of the whole map and for subsets of the hottest and coldest points.

This article is a presentation of a project which is a statistical study of white dwarfs’ properties carried out based on the sample of the First Byurakan Survey Blue Stellar Objects (FBS BSOs) and the Catalogue of White Dwarfs. Using these results, we have searched and will continue to search for new white dwarfs by means of Gaia accurate astrometry. The discovery and study of new White Dwarfs (WDs) is extremely important for understanding the kinematics and dynamics of the local stellar population. They are evolutionary signatures of the Milky Way, as most of stars pass through this evolutionary stage. We have carried out a statistical analysis of the White Dwarfs Catalogue to establish their average physical properties. Based on these data, we have searched for new WDs using Gaia EDR3 accurate astrometry. It provides huge amount of data to confirm WDs and reveal many more such objects. Gaia’s astrometric accuracy allows more detailed studies of WDs and many other stars. Using Gaia accurate data in combination with SDSS and DFBS low-dispersion spectra and additional multiwavelength data, we have revealed many new WDs. Many of them are subject for studies on binarity and variability (including a number of subtypes, e.g. ZZ Ceti stars (pulsating WDs), cataclysmic variables, etc.). WDs among FBS blue stellar objects at high galactic latitudes have been searched and revealed. Search for high galactic latitude WDs in DFBS have also been carried out. Using the revealed and calculated characteristics, a statistical study of WD properties is being done.

The analysis of the electron acceleration by the quasi-stationary sub-Dreiser electric fields in the lower solar atmosphere has been done. It has been shown that the Dreiser electric field turned out to be several orders of magnitude larger than coronal values due to the inelastic collisions between electrons and hydrogen atoms. The ionization of hydrogen atoms gives rise to the resulting secondary electrons, which become runaway under the action of sub-Dreiser electric fields. This causes an further avalanche-like ionization of the plasma and leads to the acceleration of the large number of fast electrons up to relativistic energies at small (≲ 100 km) distances.

Sunspot groups are often used as tracers to probe the differential rotation of the Sun. However, the results on the rotation rate variation obtained by different authors are not always in agreement. The reason for this might be a number of effects. In particular, faster decay of the following part of a sunspot group results in a false apparent shift of the area-weighted center of the group toward the leading part. In this work we analyze how significantly this effect may contribute to the derived rotation rate. For a set of 670 active regions, we compare the rotation rate derived from continuum intensity images to that derived from line-of-sight magnetograms. We found that the difference between the calculated rotation rates is 0.45° day −1 on average. This value is comparable to the difference between the rotation rate of the solar surface near the equator and at 30° latitude. We conclude that the accuracy of the rotation rate measurements using white-light images is not satisfactory. Magnetograms should be used in future research on the differential rotation of the Sun.

Observations in the near-infrared wavelength range have been regularly carried out at the Crimean Astrophysical Observatory (CrAO) on the Tower Solar Telescope (TST-2). It began in the late 1990s by putting into operation the Universal Spectrophotometer (USPh) at the TST-2 and it continues up to the present time. In 2020 the observation process was modernized - the mirror control electronics and software were replaced. Work is currently underway to create a catalog of solar disk images obtained before the modernization of TST-2. Here we present fragments of the catalog - several examples of a full solar disk in He i 1083 nm from the USPh/TST-2 instrument and a brief description of the future catalog.