Kinematics and Physics of Celestial Bodies最新文献

A mechanism for the origin of Kuiper belt (KB) bodies different from the hitherto known mechanisms is proposed. The distributions of the orbital elements of most of the bodies of the hot component of the KB are analyzed. The shape of the distributions indicates that all of these bodies could have appeared as a result of the destruction of a single massive body (Kuiper belt planet, KBP). The separation velocities of the fragments were determined mainly by the linear velocities of the parts of the KBP at different depths and latitudes. The maximum separation velocity corresponded to the linear velocity on the surface of the KBP near the equator and could be 2.4 km/s. The size of the KBP could be either slightly smaller or larger than the size of the Earth. The spin period was approximately 4 h. The KBP spin axis was inclined at a slight angle to the ecliptic plane, and it was directed toward the Sun at the time of destruction. This mechanism is in good agreement with current observational data. It can explain the large number of bodies with satellites in the KB as well as the revealed dependence of the average density of bodies on their size. According to this mechanism, the spin axes of the formed debris (primarily large ones) should be inclined at small angles to the ecliptic plane. The spin axes of the dwarf planets Pluto and Haumea are inclined to the ecliptic plane at angles of 23° and 10°, respectively. The future data on the coordinates of the poles of other large KB bodies can become the final confirmation of the proposed mechanism.

A comprehensive modeling of the processes in all geospheres caused by the fall and explosion of the Yushu meteoroid in the Qinghai Province (People’s Republic of China) on December 22, 2020, was performed. The magnetic, electrical, electromagnetic, ionospheric, and seismic effects, as well as the effects of acoustic-gravity waves, were estimated. It is shown that the magnetic effect of turbulence was insignificant. The magnetic effect of the ionospheric currents and the current in the meteoroid’s wake could be significant (~1 nT). Due to the capture of electrons in the field of the atmospheric gravity wave, the magnetic effect could reach the order of 1 nT. The effect of the external electric field could lead to a short-term current pulse of up to 10⁴ A. The electrostatic effect could be accompanied by the accumulation of a charge of 1–10 mC with an electric field strength of approximately 1 MV/m. The flow of electric current in the wake could lead to the emission of an electromagnetic pulse in the frequency range of approximately 10 kHz with a strength of 3–30 V/m. It was found that the electromagnetic effect of infrasound could be significant (approximately 3–20 V/m and 10–60 nT). Absorption of the shock wave at the heights of the dynamo region of the ionosphere (100–150 km) could be accompanied by the generation of secondary atmospheric gravity waves with a relative amplitude of 0.1–1. The passage of the meteoroid led to the formation of a plasma wake and to a noticeable disturbance of not only the lower but also the upper atmosphere at distances of at least 1000 km. The occurrence of an electrophonic effect seems unlikely. The possibilities of generating ion and magnetic sound by infrasound as well as gradient-drift and drift-dissipative instabilities are discussed. The magnetic, electrical, and electromagnetic effects discussed in this article partially fill in the gaps in the theory of the physical effects of meteoroids in the Earth–atmosphere–ionosphere–magnetosphere system. The magnitude of the earthquake caused by the meteoroid explosion did not exceed 2.5. The average fall rate of celestial bodies similar to the Yushu meteoroid is 0.49 year^–1.

The photometric characteristics in the midinfrared range of compact galaxies with ionizing radiation leakage (LyC galaxies) are studied to find relationships that would enable the quantitative assessment of the ionizing radiation that goes beyond the galaxy. In particular, the relationships between the color characteristics of galaxies according to data from the WISE space telescope and radiation fraction f_esc(LyC) in the Lyman continuum and radiation fraction f_esc(Ly_α) in the Ly_α line, which go beyond the galaxy, are investigated. The dependences of f_esc(LyC) and f_esc(Ly_α) on color index W1–W4 are established from the WISE space telescope data, where W1 and W4 are apparent stellar magnitudes at wavelengths of 3.4 and 22 μm, respectively. This makes color index W1–W4 a useful indicator for quantifying f_esc(LyC) and f_esc(Ly_α) in addition to the previously established some characteristics of LyC galaxies in the optical and ultraviolet ranges. Thus, the radiation of galaxies in the midinfrared range can be used to search for candidates for leaking LyC galaxies with the purpose of their further observations.

The Simeiz–Katzively Crimean geodynamic test area is one of the unique site in the world, in which several space geodesy observation stations are located, namely, RT-22 radio telescope (CRIMEA, CDP no. 7332), satellite laser ranging (SLR) stations 1873 Simeiz and 1893 Katzively, permanent GNSS stations CRAO and KTVL, and the marker of mobile SLR station 7561 Simeiz. Four local survey geodetic campaigns and five GNSS campaigns were performed to determine local ties between space geodesy stations and basic markers on this site. As a result of campaigns, the coordinates of points (space geodesy stations and markers) in the Simeiz–Katzively Crimean geodynamic test area in the ITRF2000 reference frame at epoch 2004.6 were estimated. Local ties between basic site points were determined as differences between positions of the corresponding points and the position of the RT-22 radio telescope. Deviations from the average values of local ties at the sites of the RT-22 radio telescope and the SLR station of CrAO vary within the limits of up to 3.6 and 6.4 mm, respectively. Actually, they are within the limits of determination errors of local ties. The wide range of local ties variations for the mobile SLR station (7561) is caused by the physical damage of this marker and excavation works carried out around it between observation campaigns. The local ties for points at the site of the SLR station of CLO of the Main Astronomical Observatory of the National Academy of Sciences of Ukraine vary in a very wide range because this site has a local movement in the southern direction with a substantial velocity. The coordinates of the space geodesy stations in the Simeiz–Katzively Crimean geodynamic test area are available in the ITRF2020 catalogue, so it was possible to compare the local ties calculated from its data with the ones obtained by processing the data of geodetic campaigns. The differences between the two types of local ties are very large (up to 45 mm). The reasons for these discrepancies could lie both in the errors of local ties obtained during the geodetic campaigns and in the errors of estimates of the space geodesy station coordinates at this site in the ITRF2020 catalog. The distance between SLR station 1893 Katzively and the RT-22 radio telescope (1893–7332) shows a special behavior due to the fact that the velocities given in the ITRF2020 catalog for all SLR stations at the Simeiz–Katzively Crimean geodynamic test area have the same values and, consequently, substantial local movements of the site around the 1893 Katzively station are not taken into account. Considering the substantial local movements of this site, the velocities of SLR stations at the Simeiz–Katzively Crimean geodynamic test area should be estimated separately for each station for future implementations of the International Terrestrial Reference System (ITRS), as has been done, for example, for permanent GNSS stations CRAO and KTVL.

The properties of 61 isolated galaxies with active nuclei (isolated AGNs) in the radio frequency range at redshifts z < 0.05 have been studied. The sample is obtained by cross-matching of the 2MIG catalog (2MASS catalog of isolated galaxies based on the 2MASS) with the Véron-Cetty catalog of quasars/AGNs. The sample is limited to a stellar magnitude of 4^m < K_s ≤ 12^m, a radial velocity of V_r < 15 000 km/s, and the distance to the nearest large satellite galaxy. These limitations indicate that the isolated AGNs have not collided with other galaxies in at least 3 billion years, and the observed activity of their nuclei is due only to physical processes occurring in the torus–accretion disk–nuclear region–supermassive black hole system. This study systematized the radio parameters of isolated AGNs by using data from various databases and the archive of terrestrial and space telescopes. Such characteristics are necessary for the further comparative study of physical properties of regions with active star formation and the active nuclei of these galaxies with the properties that manifest themselves when observing other spectral ranges. As a result, the radio flux densities available from the databases at a frequency of 1.4 or 5 GHz for isolated AGNs from the 2MIG catalog are given. Among the 61 galaxies of the sample, flux densities at 1.4 GHz have been found for 51 galaxies. These values are in the range of 3–20 mJy for most isolated AGNs and in the range of 50–200 mJy for two galaxies PGC35009 and NGC6951, while two galaxies ESO483-009 and ESO097-013 have spectral flux densities of 352 and 1200 mJy, respectively. The flux densities of ten isolated AGNs are less than 3 mJy. Radio flux densities of NGC0157 are not related to the position of this galaxy. Ratio R of the spectral flux densities in the radio frequency range to those in the optical bands have been calculated. Since the flux densities at 5 GHz are measured only for eight isolated AGNs, the required values of spectral flux densities at 5 GHz on the basis of relationship S_ν ∝ ν^–α for galaxies of the Seyfert type have been calculated by using the radio flux density values at 1.4 GHz and assuming that the spectral index is equal to α = 0.7. The radio fluxes densities at 5 GHz are lower than 3 mJy for 27 isolated AGNs, are in the range of 4–15 mJy for 15 AGNs, and in the range of 15–55 mJy for seven AGNs, while two galaxies ESO097-013 and ESO483-009 have radio fluxes densities of 304 and 132 mJy, respectively. We have found that 51 isolated AGNs are radio quiet sources (R < 10), the radio properties of nine objects are absent, and ESO483-009 is a radio loud galaxy (R = 20.72, Sy3/LINER, and SAB00 pec). We propose the observational methods to determine the flux densities of radio quite isolated AGNs. In conclusion, the systematization of the propert

The most important event in astronomy and celestial physics in the early 21st century is the fall of the Chelyabinsk meteoroid with a kinetic energy of nearly 440 kt TNT. Such an event occurs once every 65 years on average. The effects of this celestial body are considered in more than 200 scientific papers. At the same time, less than 25 papers are devoted to the fall of another large meteoroid called the Kamchatka meteoroid on December 18, 2018, at 23:48:20 UT (Universal time). Meanwhile, the parameters of this meteoroid are quite unique. The velocity components are v_x = 6.3, v_y = –3, and v_z = –31.2 km/s, and the velocity magnitude was 32 km/s. The total optical radiated energy was E_r = 1.3 × 10¹⁴ J (31 kt of TNT), the fireball explosion altitude was z_r = 26 km, and the coordinates are 56.9° N, 172.4° E. The angle of entry into the atmosphere with respect to the horizon was close to 68.6°. The meteoroid had the initial kinetic energy of 173 kt of TNT, the mass of 1.41 kt, and the size of nearly 9.4 m. The fall of such bodies occurs at a frequency of once every 30 years. It is of interest to perform the further study of its ionospheric effects and compare the results measured by ground-based and satellite methods with each other. The objective of this study is to analyze the results of GPS observations for the ionospheric effects to compare them with the results measured by the method of ground-based oblique incidence sounding of the ionosphere. To observe the ionospheric disturbances following the fall of the Kamchatka meteoroid, an AC60 receiving station (geographic coordinates, 53° N, 173° E) located at a distance of 450 km from the Kamchatka meteoroid explosion site and six GPS satellites (PRN02, PRN05, PRN07, PRN09, PRN29, and PRN30) were used. The principal results of these studies are the following. GPS technologies were used to estimate the delay times of ionospheric response to the Kamchatka meteoroid explosion, the horizontal propagation velocities of disturbances (504–520 m/s) and their periods (11–18 min), durations (22–35 min), wavelengths (333–530 km), and the relative amplitudes of electron density disturbances (3–4%). The estimate obtained for the relative amplitudes of wave disturbances in the electron density by the ground-based and satellite methods have proven to be close to each other (3–4%). Their periods also have close values (10–15 min). The ground-based and satellite methods also revealed the wave disturbances associated with both atmospheric gravity and seismic waves.

Multiyear researches show that weak and moderate magnetic storms may induce considerable and unpredictable changes in the ionosphere state. The problems of predicting the ionosphere response in a certain region to space weather changes currently remain topical since the physical processes occurring in the ionospheric plasma are variable and complicated. Particular interest is attracted by ionospheric disturbances with variable phases at middle latitudes and their propagation to low latitudes and the occurrence of strong ionospheric storms as a result of moderate or weak magnetic storms. The objective of this study is to perform the experimental studies of variations in the ionospheric plasma parameters over Ukraine during the very moderate magnetic storm on December 18, 2019. The study was carried out by using the incoherent scatter of radio waves as providing the most complete diagnostic capabilities and the vertical sounding method. Observations were performed in the Ionospheric Observatory of the Institute of Ionosphere (National Academy of Sciences of Ukraine, Ministry of Education and Science of Ukraine, Kharkiv) with an incoherent scatter radar. The critical frequencies were measured with a portable ionosonde. In addition, the geophysical information about the space weather and magnetosphere parameters was used. The ionosphere response to the geospace storm on December 18, 2019, over Kharkiv was analyzed. The very moderate magnetic storm (K_p = 4) was established to induce positive ionospheric disturbance. An increase in the critical frequency (up to 1.6 times) and a corresponding increase in the ionospheric F2 peak electron density (up to 2.6 times) was accompanied by a sequence of changes in the variations of principal ionospheric plasma parameters, such as the F2 layer peak height (a decrease by 30 km), the electron density throughout the entire range of studied altitudes (200–450 km), the electron and ion temperatures, and the vertical ionospheric plasma velocity component (with a decrease in the downward plasma drift velocity V_z at the noon after the magnetic storm began with further velocity recovery, the occurrence of fluctuations in the variations V_z with a quasi-period of 1 h 50 min at 15:40 UT (Universal Time) at altitudes of 360–420 km, and weakening of the evening extremum effect in the V_z variations and a maximum decrease in the velocity to 40–70 m/s at these altitudes). A substantiation was given for the following mechanism of the formation of a positive ionospheric storm: the downward plasma drift is weakened in the mid-latitude ionosphere during the winter daylight due to the fact that normal circulation is weakened by reverse storm-induced circulation. The very moderate magnetic storm on December 18, 2019, induced appreciable changes in the ionospheric plasma parameters throughout the entire range of studied altitudes. The measured data

The concept of a device for the radiometric calibration of photometers or polarimeters on the Earth orbit using the Sun is considered. The shortcomings and advantages for the designing and materials of the key elements are analyzed. The illumination conditions are determined for the working element of the radiometric calibration assembly of the ScanPol scanning polarimeter aboard the YuzhSat satellite platform for different configurations in different orbit locations. The satellite orbit sections where solar illumination is optimal for the working element of this assembly from the viewpoint of the relation between the incidence and observation angles and minimization of the light caused by reflection from the Earth surface, atmosphere, ScanPol structure elements, and satellite platform are specified. The obtained results are planned for use in the development of an optimal design for the ScanPol radiometric calibration assembly to provide a necessary radiometric measurements precision during the Aerosol-UA space mission.

We obtained equations for determining the star-formation rate in local compact star-forming galaxies from the SDSS Data Release 16 using luminosities of the forbidden emission lines [O II] λ 372.7 nm, [Ne III] λ 386.8 nm, [O III] λ 495.9 nm, and [O III] λ 500.7 nm and their combinations. The equations are based on the assumption that the star-formation rates, determined from the luminosity of the forbidden lines and H_β emission lines, are equal. This approach is especially useful because the observation of H_β emission is not always possible. For example, in galaxies with redshift z > 1, this line goes beyond the optical range, and the [O II] λ 372.7 nm line, the [Ne III] λ 386.8 nm line, or their combination can be used instead. On the other hand, in many studies of faint objects using low-resolution spectra, the H_β line merges with the stronger [O III] λ 495.9 nm and [O III] λ 500.7 nm lines. In these cases, [O III] lines and their combination can be used to determine the rate of star formation. The resulting equations can be applied to compact star-forming galaxies in a wide range of redshifts.

This study is aimed at investigating the dynamic evolution of the orbits of stellar globular clusters (SGCs). To integrate the orbits backward in time, the authors use models of the time-varying potentials derived from cosmological simulations, which are closest to the potential of the Galaxy. This allows for estimating the probability of close passages (“collisions” herein) of SGCs with respect to each other and the Galactic center (GC) in the Galaxy undergoing dynamic changes in the past. To reproduce the dynamics of the Galaxy in time, five of the 54 potentials previously selected from the IllustrisTNG-100 large-scale cosmological database, which are similar in their characteristics (masses and dimensions of the disk and halo) to the current physical parameters of the Milky Way, are used. With these time-varying potentials, we have reproduced the orbital trajectories of 143 SGCs 10 billion years back in time using our original φ-GPU high-order N-body parallel dynamic computer code. Each SGC was treated as a single physical particle with the assigned position and velocity of the cluster center from the Gaia DR2 observations. For each of the potentials, 1000 initial conditions were generated with randomized initial velocities of SGCs within the errors of the observational data. In this study, we consider close passages to be passages with a relative distance of less than 100 pc and a relative speed of less than 250 km s^–1. Clusters that pass at longer distances and/or with higher velocities do not have a substantial dynamic effect on the orbits of SGC. In our opinion, the largest changes in the orbits of clusters can be caused by clusters that pass with low velocities at distances smaller than several fold (for example, fourfold) the sum of the radii of the cluster half-masses. Therefore, the authors regard such close passages separately (for brevity, we will call such passages “collisions”). To select clusters that pass at close distances from the GC, the following criterion is applied based only on the relative distance: it must be less than 100 pc. Applying the above criteria, the authors obtained statistically significant rates of close passages of SGCs with respect to each other and to the GC. It has been determined that SGCs during their evolution have approximately ten intersecting trajectories with each other on the average and approximately three to four close passages near the GC in 1 billion years at a distance of 50 pc for each of the chosen potentials.