Volume 29, Issue 1

The mass measurement of supermassive black holes (SMBHs) is a very complex task. Between several methods for SMBH mass measurements, some of them use the spectral lines, which indicate the motion of the emitting/absorbing material around an SMBH. Mostly, there is an assumption of virialization of line emitting gas in the region which is close to the central SMBH. In this paper we will give an overview of methods for the SMBH mass measurements using broad emission spectral lines observed in Type 1 AGNs. First we give the basic idea to use the parameters of broad lines to SMBH mass measurements. After that we give an overview of broad lines from X-ray (Fe kα) to the IR (Pashen and Brecket lines) which have been used for SMBH mass estimates. Additionally, we describe and discuss a new method for SMBH mass measurements using the polarization in the broad lines emitted from Type 1 AGNs.

Previous observations of a large number of galaxies show differences between the photometry of spiral galaxies with clockwise spin patterns and spiral galaxies with counterclockwise spin patterns. In this study the mean magnitude of a large number of clockwise galaxies is compared to the mean magnitude of a large number of counterclockwise galaxies. The observed difference between clockwise and counterclockwise spiral galaxies imaged by the space-based COSMOS survey is compared to the differences between clockwise and counterclockwise galaxies imaged by the Earth-based SDSS and Pan-STARRS around the same field. The annotation of clockwise and counterclockwise galaxies is a fully automatic process that does not involve human intervention, and in all experiments both clockwise and counterclockwise galaxies are separated from the same fields. The comparison shows that the same asymmetry was identified by all three telescopes, providing strong evidence that the rotation direction of a spiral galaxy is linked to its luminosity as measured from Earth. Analysis of the luminosity difference using a large number of galaxies from different parts of the sky shows that the difference between clockwise and counterclockwise galaxies changes with the direction of observation, and oriented around an axis.

Solar activity affects geophysical and heliophysical processes. Long-term changes in solar activity are closely related to climate change. Solar physicists and earth science researchers need longer observations of solar activity. Current continuous observations of solar activity are only about 400 years. Some scholars have compiled naked-eye observations of sunspots from 200 BC to 1918 AD from historical documents. In this present work, the authors use the weighted wavelet transform to study the observations series. The results show the Suess - de Vries cycle with a period from 195- to 235-year existing in the discontinuous sunspot series. Meanwhile, the cycle signal changes with time. Especially, the Suess/de Vries cycle is relatively obvious from 200 BC to 400 AD, 800 AD to 1340 AD, 1610 AD to 1918 AD, with a period of about 211-year, about 195-year, and about 235-year, respectively.

In this manuscript, the temperature model of multilayer insulation (MLI) on a spacecraft solar panel in thermal radiation is considered. The thermal insulation performance of MLI and the stress of the spacecraft are also considered. The thermal equilibrium equation of the surface temperature of MLI spacecraft in the presence of current transfer, and the iterative temperature acquisition algorithm of the front and back surface of solar panel MLI are derived. The Gaussian elimination method is used to invert the high order sparse matrix composed of error coefficients, thus realizing the real-time calculation of thermal re-radiation(TRR). The thermodynamic model was applied to the motion simulation of GPS Block IIR satellites, and the theoretical model was verified based on the actual temperature measurement data of several GPS Block IIR satellites. The simulation results have certain reference value for studying the thermodynamic modeling of MLI spacecraft and TRR perturbation calculation.

The studied conjecture is that ultra high energy cosmic rays (UHECRs) are hypothetical Planck neutrinos arising in the decay of the protons falling onto the gravastar. The proton is assumed to decay at the Planck scale into positron and four Planck neutrinos. The supermassive black holes inside active galactic nuclei, while interpreted as gravastars, are considered as UHECR sources. The scattering of the Planck neutrinos by the proton at the Planck scale is considered. The Planck neutrinos contribution to the CR events may explain the CR spectrum from 5 × 10 18 eV to 10 20 eV. The muon number in the Planck neutrinos-initiated shower is estimated to be larger by a factor of 3/2 in comparison with the standard model that is consistent with the observational data.

The hypothesis on the role of the meteoroid impacts in the comet nuclei splitting as well as acceleration of their heliocentric velocity are considered. Inclinations of the orbits of split comets relative to the movement planes of 100 known meteoroid streams are calculated. The analysis is carried out for the cases: when the cometary nodes are located from the meteoroids orbit < 0.1 AU; MOID-values less than 0.1 AU. In the case of split long-period comets irregularity (maximum near 180°) of the distribution of the inclinations has been found. Comets, constituting this maximum, could have head-on collisions with meteoroids. A similar analysis is carried out relatively to the hyperbolic comets (HCs). Analysis is based on the assumption that the acceleration of the heliocentric velocities of the comet also is caused by collisions with meteoroids. The inclinations of the orbits of 300 HCs relative to 100 known meteoroid streams have the significant maxima in the interval of 90°− 101.5°. Acceleration of comet velocity might be the result of “slanting” collisions with meteoroids.

The active galactic nuclei (AGN) are among the most powerful sources with an inherent, pronounced and random variation of brightness. The randomness of their time series is so subtle as to blur the border between aperiodic fluctuations and noisy oscillations. This poses challenges to analysing of such time series because neither visual inspection nor pre-exisitng methods can identify well oscillatory signals in them. Thus, there is a need for an objective method for periodicity detection. Here we review our a new data analysis method that combines a two-dimensional correlation (2D) of time series with the powerful methods of Gaussian processes. To demonstrate the utility of this technique, we apply it to two example problems which were not exploited enough: damped rednoised artificial time series mimicking AGN time series and newly published observed time series of changing look AGN (CL AGN) NGC 3516. The method successfully detected periodicities in both types of time series. Identified periodicity of ~4 yr in NGC 3516 allows us to speculate that if the thermal instability formed in its accretion disc (AD) on a time scale resembling detected periodicity then AD radius could be ~0.0024 pc.

In our study of the validity of Hawking’s predicted radiation temperature of a black-hole, we found that the calculated temperature is another form of Zeldovich’s expression for the cosmological constant. We reasoned that as Zeldovich predicted the extreme value of cosmological constant thus Hawking might have also predicted an extreme temperature. However, the actual temperature might be something different. This result implies that all predictions based on Hawking’s radiation temperature might be incorrect.

We investigated the dynamical behavior in the potential of the primary in the triple asteroid (45) Eugenia with the calculation of the full gravitational potential caused by its 3D irregular shape. We presented the whole structure of the gravitational potential and the effective potential of (45) Eugenia in the coordinate planes, and showed the surface height, surface gravitational force accelerations, and the surface effective potential. The surface gravitational environment has been discussed. The zero-velocity curves and the position of external equilibrium points are calculated and showed relative to the 3D shape of the asteroid to help compare the relationship of the characteristic of the gravitational potential and the shape of the asteroid. There are five equilibrium points in the gravitational potential (45) Eugenia. We presented the positions, eigenvalues, topological cases, and stability of these equilibrium points. To analyze the variety of the orbital parameters close to (45) Eugenia, we computed two different orbits and compared the results. The mechanical energy, the semi-major axis, and the eccentricity have two different periods: the long period and the short period. The inclination have three different periods, an intermediate period is occurred. The longitude of the ascending node and the argument of periapsis not only have two periodic terms, but also have a secular term.

New observations of the eclipsing binary system V1848 Ori were carried out using the V filter resulting in a determination of new times of minima and new ephemeris were obtained. We presented the first complete analysis of the system’s orbital period behavior and analysis of O-C diagram done by the GA and MCMC approaches in OCFit code. The O-C diagram demonstrates a sinusoidal trend in the data; this trend suggests a cyclic change caused by the LITE effect with a period of 10.57 years and an amplitude of 7.182 minutes. It appears that there is a third body with mass function of f ( m 3 ) = 0.0058 M⊙ in this binary system. The light curves were analyzed using the Wilson-Devinney code to determine some geometrical and physical parameters of the system. These results show that V1848 Ori is a contact W UMa binary system with the mass ratio of q = 0.76 and a weak fillout factor of 5.8%. The O’Connell effect was not seen in the light curve and there is no need to add spot.

We present an investigation of halo coronal mass ejections (HCMEs) kinematics and other facts about the HCMEs. The study of HCMEs is very important because HCMEs are regarded as the main causes of heliospheric and geomagnetic disturbances. In this study, we have investigated 313 HCMEs observed during 1996-2012 by LASCO, coronal holes, and solar flares. We find that HCMEs are of two types: accelerated HCMEs and decelerated HCMEs. The mean space speed of HCMEs is 1283 km/s while the mean speed of decelerated HCMEs and accelerated HCMEs is 1349 km/s and 1174 km/s, respectively. The investigation shows that 1 (0.3%) HCME was associated with class A SXR, 14 (4.7%) HCMEs were associated with class B SXR-flares, 87 (29.4%) HCMEs were associated with class C SXR-flares, 125 (42.2%) HCMEs were associated with class M SXR-flares and 69 (23.3%) HCMEs were associated with class X SXR-flares. The speed of HCMEs increases with the importance of solar SXR-flares. The various results obtained in the present analysis are discussed in the light of the existing scenario of heliospheric physics.

In this paper, we have investigated the homogeneous and anisotropic Bianchi type– I cosmological model with a time-varying Newtonian and cosmological constant. We have analytically solved Einstein’s field equations (EFEs) in the presence of a stiff-perfect fluid. We show that the analytical solution for the average scale factor for the generalized Friedman equation involves the hyper-geometric function. We have studied the physical and kinematical quantities of the model, and it is found that the universe becomes isotropic at late times.

The increase in space debris orbiting Earth is a critical problem for future space missions. Space debris removal has thus become an area of interest, and significant research progress is being made in this field. However, the exorbitant cost of space debris removal missions is a major concern for commercial space companies. We therefore propose the debris removal using electromagnetic launcher (DREL) system, a ground-based electromagnetic launch system (railgun), for space debris removal missions. The DREL system has three components: a ground-based electromagnetic launcher (GEML), suborbital vehicle (SOV), and mass of micrometer-scale dust (MSD) particles. The average cost of removing a piece of low-earth orbit space debris using DREL was found to be approximately USD 160,000. The DREL method is thus shown to be economical; the total cost to remove more than 2,000 pieces of debris in a cluster was only approximately USD 400 million, compared to the millions of dollars required to remove just one or two pieces of debris using a conventional space debris removal mission. By using DREL, the cost of entering space is negligible, thereby enabling countries to remove their space debris in an affordable manner.

A two-step identification method is proposed, both the moment of inertia and the mass properties are identified. A new index parameter which is different from the commonly used condition number is first defined for designing the optimal excitation. A method is introduced based on the least squares algorithm. Detailed mathematical equations and numerical analysis are proposed. Simulation results show that the proposed method can identify the mass parameters of spacecraft.

In the space of the entire universe, the only conclusive evidence of life, is found on Earth. Although the ultimate source of all life is unknown, many investigators believe Earth, Mars, and Venus may have been seeded with life when these planets, and the sun, were forming in a galactic cluster of thousands of stars and protoplanets. Yet others hypothesize that while and after becoming established members of this solar system, these worlds became contaminated with life during the heavy bombardment phase when struck by millions of life-bearing meteors, asteroids, comets and oceans of ice. Because bolide impacts may eject tons of life-bearing debris into space, and as powerful solar winds may blow upper atmospheric organisms into space, these three planets may have repeatedly exchanged living organisms for billions of years. In support of these hypotheses is evidence suggestive of stromatolites, algae, and lichens on Mars, fungi on Mars and Venus, and formations resembling fossilized acritarchs and metazoans on Mars, and fossilized impressions resembling microbial organisms on the lunar surface, and dormant microbes recovered from the interior of a lunar camera. The evidence reviewed in this report supports the interplanetary transfer hypothesis and that Earth may be seeding this solar system with life.

Based on the Defense Meteorological Satellite Program (DMSP) observations during Solar Cycle 23, this paper examines solar activity dependence of ionospheric bulk ion upflow events (IUEs) in the Southern Hemisphere (SH). Much previous similar work was conducted over the Northern Hemisphere (NH) with measurements from European Incoherent Scatter (EISCAT). To eliminate the influence of geomagnetic disturbance on IUEs, we pick out observations during geomagnetic quiet periods (with Kp ≤ 2 + ). Results show that, ion upward densities and fluxes are dramatically elevated at times of high solar activity (HSA) but ion upward drifts and occurrences are increased at times of low solar activity (LSA) in the SH, which is consistent with the situation in the NH. The ratios between HSA and LSA for these four parameters (IUEs’ density, flux, upward drift and occurrence) are ~2.71, ~1.98, ~0.76 and ~0.57, respectively. Furthermore, lower flux event takes place frequently at LSA as the background ion density is low but the upward drift is large, while higher flux event happens commonly at times of HSA accompanied by high ion density but low upward velocity. Quantitatively, an increase in unit of solar activity (characterized by P index) causes a 4.2×10 8 m −3 increase in ion density and a 1.2×10 11 m −2 ·s −1 enhancement in upward flux, together with a 0.6 m·s −1 and 0.02 % decrease in ion upward velocity and uprate, respectively. The acceleration from the ambipolar electric field is thought to be a possible mechanism affecting the dependence of IUEs on solar variations. For HSA, the acceleration from the ambipolar electric field weakens, but a large number of background ions provide abundant seeds for acceleration and upflow, which maintains a high IUE flux. It is inferred that upflow events and upward drifts are inhibited by the enhanced ionospheric background density.

We use the distributions of spectral indices (α v ) of a large homogenous sample of Fermi -detected blazars to re-investigate the relationship between flat spectrum radio quasars (FSRQs) and subclasses of BL Lac objects (BL Lacs). We compute the broadband synchrotron and Compton spectral indices from radio-to-X-ray and X-ray to y -ray bands, respectively. Analyses of our data show continuity in the distributions of the spectral indices from FSRQs to HSP through LSP and ISP subclasses of BL Lacs. We find from y -ray luminosity distribution that the jetted radio galaxies form the low-luminosity tail of the distribution, which is suggestive that the sequence can be extended to the young jetted galaxy populations. We observe a significant difference in the shape of Compton and synchrotron spectra: significant anti-correlation ( r ∼−0.80) exists between the broadband Compton and synchrotron spectral indices. Furthermore, the broadband spectral indices vary significantly with redshift ( z ) at low redshift ( z < 0.3) and remain fairly constant at high ( z ≥ 0.3) redshift. The trend of the variations suggests a form of evolutionary connection between subclasses of blazars. Thus, while selection effect may be significant at low redshift, evolutionary sequence can also be important. Our results are not only consistent with a unified scheme for blazars and their young jetted galaxy counterparts but also suggest that the broadband spectral sequence of blazars is not a secondary effect of redshift dependence.

This paper is devoted to the discovery of 37 asteroids at the Baldone Astrophysical Observatory (MPC 069) from 2015 to 2018, and one of dynamically interesting Mars-crosser (MC) observed at the Baldone Astrophysical Observatory, namely 2008 LX16. In Baldone Observatory, was independently discovered the Near-Earth Object 2018 GE3 on the image of 13 April 2018. Also, the NEO 2006 VB14 was observed doing its astrometry and photometry. Moreover, we observed asteroids 1986 DA and 2014 LJ1. We computed orbits and analyzed the orbital evolution of these asteroids. 566 positions and photometric observations of NEO objects 345705 (2006 VB14) and 6178 (1986 DA) were obtained with Baldone Schmidt telescope in 2018 and 2019. We detected their rotation period and other physical characteristics. Also, a Fourier transform was applied to determine the rotation period of asteroid 6178 (1986 DA). Value (3.12 ± 0.02)h was obtained. Our observations confirm the previously obtained rotation periodP=3.25hfor2006VB14.

The discovery and subsequent investigations of atmospheric oxygen on Mars are reviewed. Free oxygen is a biomarker produced by photosynthesizing organisms. Oxygen is reactive and on Mars may be destroyed in 10 years and is continually replenished. Diurnal and spring/summer increases in oxygen have been documented, and these variations parallel biologically induced fluctuations on Earth. Data from the Viking biological experiments also support active biology, though these results have been disputed. Although there is no conclusive proof of current or past life on Mars, organic matter has been detected and specimens resembling green algae / cyanobacteria, lichens, stromatolites, and open apertures and fenestrae for the venting of oxygen produced via photosynthesis have been observed. These life-like specimens include thousands of lichen-mushroom-shaped structures with thin stems, attached to rocks, topped by bulbous caps, and oriented skyward similar to photosynthesizing organisms. If these specimens are living, fossilized or abiogenic is unknown. If biological, they may be producing and replenishing atmospheric oxygen. Abiogenic processes might also contribute to oxygenation via sublimation and seasonal melting of subglacial water-ice deposits coupled with UV splitting of water molecules; a process of abiogenic photosynthesis that could have significantly depleted oceans of water and subsurface ice over the last 4.5 billion years.

During re-entry objects with low-eccentricity orbits traverse a large portion of the dense atmospheric region almost every orbital revolution. Their perigee decays slowly, but the apogee decays rapidly. Because ballistic coefficients change with altitude, re-entry predictions of objects in low-eccentricity orbits are more difficult than objects in nearly circular orbits. Problems in orbit determination, such as large residuals and non-convergence, arise for this class of objects, especially in the case of sparse observations. In addition, it might be difficult to select suitable initial ballistic coefficient for re-entry prediction. We present a new re-entry prediction method based on mean ballistic coefficients for objects with low-eccentricity orbits. The mean ballistic coefficient reflects the average effect of atmospheric drag during one orbital revolution, and the coefficient is estimated using a semi-numerical method with a step size of one period. The method is tested using Iridium-52 which uses sparse observations as the data source, and ten other objects with low-eccentricity orbits which use TLEs as the data source. We also discuss the performance of the mean ballistic coefficient when used in the evolution of drag characteristics and orbit propagation. The results show that the mean ballistic coefficient is ideal for re-entry prediction and orbit propagation of objects with low-eccentricity orbits.

In this work we aimed to develop the image reconstruction algorithm without any analytical simplifications and restrictions. In our method we abandon Fourier’s approach to image reconstruction, and instead use the number of counts recorded in each detector pixel, and then reconstruct each image using a classical Richardson-Lucy algorithm. Among similar works performed in the past, our approach is based, for the first time, on the real geometry of STIX. We made a preliminary analysis of expected differences in STIX imaging which may occur due to usage of slightly different geometries. The other difference is that we use single-pixel-response maps. Namely, knowing the instrument geometry we are able to calculate the detector response for point sources covering entire the solar disc. Next, we iteratively combine them with varying weights until the best match between reconstructed and observed detector responses is achieved. Preliminary tests revealed that the developed algorithm reproduces high quality images. The algorithm is moderately fast, but the result comparable to CLEAN algorithm is obtained within 20-50 iteration steps which takes less than 2 seconds on typical portable computer configuration. The location, size and intensity of reconstructed sources are very close to simulated ones. Therefore the algorithm is very well suited for the detailed photometry of the solar HXR sources. Moreover, its simplicity allows to improve photon transmission calculation in case of any grids uncertainties measured after the launch.

Among different models for determining the habitable zone (HZ) around a star, a Latitudinal Energy Balance Model (LEBM) is very beneficial due to its parametricity which keeps a good balance between complexity and simulation time. This flexibility makes the LEBM an excellent tool to assess the impact of some key physical parameters on the temperature and the habitability of a planet. Among different physical parameters, some of them, up until now, cannot be determined by any method such as the planet’s spin obliquity, diurnal period, ocean-land ratio, and pressure level. Here we apply this model to study the effect of these unknown parameters on the habitability of three exoplanets located in the inner, outer, and middle of their optimistic HZ. Among the examined parameters, the impact of pressure is more straightforward. It has a nearly direct relation with temperature and also with the habitability in the case of a cold planet. The effect of other parameters is discussed with details. To quantify the impact of all these unknown parameters we utilize a statistical interface which provides us with the conditional probability on habitability status of each planet.

Lunar exploration is a significant process to unravel the evolutionary history of the Earth-Moon system and the pivotal foundation for the exploration of the solar system. A total of 49,161 articles recorded in a comprehensive online literature database between 1959 and 2018 were reviewed to address the development of lunar science in six aspects: publication output volume, keywords, journals, authorship, collaboration, and national output efficiency. The development of lunar science experienced rise and fall corresponding to a log-linearized model that could be clearly divided into three stages: space race (1959-1977), silent stage (1978-1996) and renaissance (1997-2018). Keywords extracted from publications as reliable predictors of multidiscipline showed that the well-developed disciplines of lunar science were astronomy, space engineering, earth and planetary science, while other disciplines played important roles in different stages. Researchers had become cooperative rather than independent in publishing in the past sixty years. Countries with higher average annual GDP contributed more to the development of lunar science. The findings of this work help scholars comprehend the development of lunar science for the past, present and future.

In this paper, the evolution of space debris for spacecraft in the Sun-Synchronous orbit has been investigated. The impact motion, the evolution of debris from the Sun-Synchronous orbit, as well as the evolution of debris clouds from the quasi-Sun-Synchronous orbit have been studied. The formulas to calculate the evolution of debris objects have been derived. The relative relationships of the velocity error and the rate of change of the right ascension of the ascending node have been presented. Three debris objects with different orbital parameters have been selected to investigate the evolution of space debris caused by the Sun-Synchronous orbit. The debris objects may stay in quasi-Sun-Synchronous orbits or non-Sun-Synchronous orbits, which depend on the initial velocity errors of these objects.

This work applies a previously suggested model of gravitational field propagation to various planetary bodies within the solar system. Primarily the goal has been to critically test the validity of this model by identifying observations which are in direct conflict with it. Specifically this model predicts a Doppler shift in gravitational acceleration (gD). Applying the model to the planets and the Sun gD acts to increase planetary spin, opposing various sources of drag. The model is seen not to be in conflict with a wide variety of observed parameters which have been treated here and is shown to quantitatively account for several observed phenomena previously thought to be unrelated and which have been di˚cult to explain conventionally. These phenomena include the internal heat generation and magnetospheric generation within the gas giants as well as super rotation which seen in most planetary atmospheres as well as the Sun as differential rotation. This model for the first time provides a quantitative prediction of the low internal heat generation seen in Uranus compared to Neptune. It also provides a novel mechanism for solar coronal heating, thermospheric heating in the gas giants and the correlation between climate and magnetosphere observed on Earth.