Significant high number commensurabilities in the main lunar problem II: The occurrence of Saros-like near periodicities

The effect of changes in the Moon's semimajor axis and the Earth's orbital eccentricity on the occurrence of Saros-like cycles is examined. The Earth-Moon-Sun dynamical system exhibits such cycles for only 25 to 30% of the time interval between –5×10⁷ to +5×10⁷ years. Not only has the present Saros the smallest period during this time, but it also has one of the longest durations and the period closest to an integral number of anomalistic years, thus making it one of the most efficient Saros-like cycles for reversing solar perturbations in the main lunar problem. During the lifetime of a Saros-like cycle, variations of the Earth's orbital eccentricity cause frequent disappearances and reappearances of the cycle.     

Lunisolar effect on the trigger of earthquakes

Dealing with moon theory and tidal dynamics and checking lists of earthquake data one can take the following two observations: 1) The first extreme proxigean spring tide in the new millennium happened on 2005 January 10, in new moon phase, and half a synodic month earlier, when the Moon was full on 2004 December 26, the Christmas Tsunami was triggered in the Indian Ocean. The next extreme tide in new moon phase will occur after one Saros cycle, on 2023 January 21. 2) The second observation is connected with the lunar evection anomaly. The time between the Whitsun Quake in China on 2008 May 12 and the Christmas Tsunami amounts to 1233 days. On the other hand, three lunar evectional cycles take 3 × U_e = 3 × 411.8 = 1235 days. These observations hint at lunisolar structures in the earthquake distribution. In the present treatise we will reveal such structures by composing lunisolar ephemerides and earthquake Tables. In particular, we use Student's t‐test and show that there is a significant relationship between the beat period U_e and the earthquake statistics (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The arrangement in mean elements space of the periodic orbits close to that of the Moon

In a simplified model of the Earth-Moon-Sun system based on the restricted circular 3-dimensional 3-body problem, it is possible to find numerically a set of 8 periodic orbits whose time evolutions closely resemble that of the Moon's orbit. These orbits have a period of 223 synodic months (i.e. the period of the Saros cycle known for more than two millennia as a means of predicting eclipses), and are characterized by a secular rotation of the argument of perigee . Periodic orbits of longer durations exhibiting this last feature are very abundant in Earth-Moon-Sun dynamical models. Their arrangement in the space of the mean orbital elements- for various values of the lunar mean motion is presented.     

空间时代地面光学天体测量的意义

从基本天体测量的主要任务出发，介绍了绝对测定和相对测量之间的区别和不同用途，并针对河外射电源参考架和依巴谷参考架的高精度的不足之处，说明了地面光学天体测量的长期性和灵活性等优势正是克服这些不足之处所必须的，但这不应是传统的已有精度下的地面光学天体测量，而应是与空间测量精度可比的要求下的地面测量，两者配合起来，将能促进本学科和相关学科的发展。     

Model of explosive eruptions of water vapor and dust on icy satellites

The possibility of generating water vapor and other gaseous products during nonvolcanic explosive eruptions in lithospheres of icy satellites is discussed. Explosive eruptions of ice, with its fragmentation into micro-and nanofragments, can occur in the extensive deep layers of such icy satellites as Europa, Ganymede, Enceladus, etc., if giant cracks are episodically formed in the lithospheres of these satellites. Such cracks can be produced by tidal forces, synchronous resonances of satellites, or especially powerful impacts. The model is based on the recently obtained experimental evidence that explosive ice instability (Bridgman effect) is formed at a strong nonuniform compression in the regions of high pressures and low temperatures. Water films, the thicknesses of which reach several microns, can be formed during the process of the mutual friction of ice fragments during their quasi-liquid flow at the instant of an explosive eruption. About 1–10 dm³ of a water film can be produced in 1 m³ of erupted ice fragments. Water vapor can be formed from a water film when this water boils up after a rapid pressure drop as a result of an ice-water mixture eruption from cracks. A certain amount of gaseous products in the form of hydrogen, oxygen, and ammonia molecules and radicals on their basis can be generated during the sputtering induced by electrons and ions and the dissociation of nanofragments of ice during the process of ice explosive fragmentation as a result of fracto-, tribo-, and secondary emission. The estimates indicate that the volume of water vapor erupted on satellites can be larger than that of discharged ionized gases by a factor of not less than 10⁵–10⁷. Water vapor and microscopic ice fragments can be erupted from cracks in the lithospheres of small Enceladus-type satellites at velocities higher than the second cosmic velocity. Gaseous products generated in such episodic processes can, most probably, substantially contribute to the density of the atmosphere that exists on small icy satellites, but can only insignificantly contribute to this density on large satellites. The stick-slip motions of the most condensed plumes of water vapor and dust, normal to the satellite surface, along the mouths of gigantic cracks may indicate that the proposed model is realistic. Such wanderings of water vapor plumes can result in the synchronous motions of thermal patches on the satellite surface along crack mouths at velocities of about 10 km/h.     

Infrared photometry of AGB stars

The goal of this article is to show that, if one avoids star forming regions, mass-losing AGB stars can generally be selected from the data that will be provided by the near-infrared surveys which are presently considered. Also, if IRAS data are available, the separation between carbon-rich and oxygen-rich stars can be operated by their positions in infrared colour diagrams. In extragalactic systems, red supergiants can be discriminated from AGB stars by their luminosities.based on observations obtained with the ESO 1-m telescope     

Computer simulation of regolith vertical structure and exposure age of small satellites of planets

The simulation has shown that the regolith layers several hundred meters thick can be formed on the small satellites of planets of Phobos and Deimos type providing that almost all the material lost at meteorite impacts return to the satellite. The existence of a global layer on Deimos that filled the craters for the depth of about 5 m can be explained by the crater presence of diameter of about 4 km and the age of less than 350 Myr on its hemisphere almost unstudied. Dust belts with dust concentration by 3 orders greater than round the Earth can exist in the region of satellite orbits.     

A new way to measure the departure from thermodynamic equilibrium in stellar atmospheres

A new way to measure the departure from thermodynamic equilibrium is proposed based on the departure factor which evaluates the deviation from a Boltzmann level distribution, used by Short and Hauschildt (2005) and others. The way is based on an explicit relationship describing the departure factor as a function of line to continuum source, dynamic temperature and line photon frequency, under three assumptions that the scattering can be neglected, the background continuum can be treated as a Planck function, and finally the complete redistribution can be true. It has the advantage that the departure can be very conveniently evaluated from the spectral analysis with only the radiative transfer involved. Some physical insights are recovered for some extreme cases.Some example calculations of the departure are presented for the quiet Sun, faint solar flare and strong solar flare for the generally used solar chromospheric lines: Hα, Hβ,CaII H, K and triplet. It is revealed that in the case of solar flares, the departure is less than thermodynamic equilibrium along the larger depth range than in the quiet sun due to chromospheric condensation. It becomes hard to distinguish the departures for the different lines of the same atom or ion. It is expected that this investigation can be constructive for studying stellar atmospheres in cases where the three assumptions are close to reality.     

Search for constraints on Lorentz violation parameters by studying the polarization of afterglows from high-energy gamma-ray bursts

The birefringence of electromagnetic radiation from gamma-ray burst (GRB) afterglows due to the Lorentz violation (LV) of spacetime has been calculated. The dependence of this effect on the radiation wavelength and redshift z in the ΛCDM model of the Universe has been established. It is shown that polarization tests for GRB afterglows can be invoked to measure the LV parameters. LV causes oscillations in the parameters of the afterglow spectrum that can be in the ultraviolet spectral range and will depend significantly on redshift z. This can facilitate the recording of LV for an electromagnetic field and can lower significantly the energy threshold of its detection.     

Viscous liquid film flow on dune slopes of Mars

It is shown that viscous liquid film flow (VLF-flow) on the surfaces of slopes of martian dunes can be a low-temperature rheological phenomenon active today on high latitudes. A quantitative model indicates that the VLF-flows are consistent with the flow of liquid brines similar to that observed by imaging at the Phoenix landing site. VLF-flows depend on the viscosity, dynamics, and energetics of temporary darkened liquid brines. The darkening of the flowing brine is possibly, at least partially, attributed to non-volatile ingredients of the liquid brines. Evidence of previous VLF-flows can also be seen on the dunes, suggesting that it is an ongoing process that also occurred in the recent past.     

Physical properties of meteorites—Applications in space missions to asteroids

Abstract— Based on reflectance spectroscopy and chemical/mineralogical remote sensing methods, it is generally assumed that asteroids are parent bodies for most meteorites reaching the Earth. However, more detailed observations indicate that differences exist in composition between asteroids and meteorites resulting in difficulties when searching for meteorite‐asteroid match. We show that among other physical parameters the magnetic susceptibility of an asteroid can be determined remotely from the magnetic induction by solar wind using an orbiting spacecraft or directly using the AC coil on the lander, or it can be measured in samples returned to the laboratory. The shape corrected value of the true magnetic susceptibility of an asteroid can be compared to those of meteorites in the existing database, allowing closer match between asteroids and meteorites. The database of physical properties contains over 700 samples and was recently enlarged with measurements of meteorites in European museums using mobile laboratory facility.     

Rotation of Tokamak Plasmas by Alfvén Waves

Externally excited Alfvén waves can generate the poloidal and toroidal rotation in the collisional (edge) and core (weakly collisional) tokamak plasma. The necessary value of these velocities to achieve the L-H transition, can be obtained by manipulating the value of an absorbed power. This rotation linearly depends on dissipated power, decreases in banana regimes and did not depend on toroidal magnetic field. In the plasma layer where the RF power is absorbed, the radial electric field also appears. There is the very satisfactory agreement between our theory and experimental results obtained on Phaedrus-T tokamak. The methods developed in this paper can be applied to other tokamaks with another kind of waves, which can be used to operate the plasma dynamics taking into account the appropriate dispersion relation for that type of waves.     

High-energy scalarons in R gravity as a model for Dark Matter in galaxies

We show that in the framework of R² gravity and in the linearized approach it is possible to obtain spherically symmetric stationary states that can be used as a model for galaxies. Such approach could represent a solution to the Dark Matter Problem. In fact, in the model, the Ricci curvature generates a high energy term that can in principle be identified as the dark matter field making up the galaxy. The model can also help to have a better understanding on the theoretical basis of Einstein-Vlasov systems. Specifically, we discuss, in the linearized R² gravity, the solutions of a Klein-Gordon equation for the spacetime curvature. Such solutions describe high energy scalarons, a field that in the context of galactic dynamics can be interpreted like the no-light-emitting galactic component. That is, these particles can be figured out like wave-packets showing stationary solutions in the Einstein-Vlasov system. In such approximation, the energy of the particles can be thought of as the galactic dark matter component that guarantees the galaxy equilibrium. Thus, because of the high energy of such particles the coupling constant of the R²-term in the gravitational action comes to be very small with respect to the linear term R. In this way, the deviation from standard General Relativity is very weak, and in principle the theory could pass the Solar System tests. As pertinent to the issue under analysis in this paper, we present an analysis on the gravitational lensing phenomena within this framework.Although the main goal of this paper is to give a potential solution to the Dark Matter Problem within galaxies, we add a section where we show that an important property of the Bullet Cluster can in principle be explained in the scenario introduced in this work.To the end, we discuss the generic prospective to give rise to the Dark Matter component of most galaxies within extended gravity.     

Breaking halo occupation degeneracies with marked statistics

We show that a suitably defined marked correlation function can be used to break degeneracies in halo-occupation distribution modelling. The statistic can be computed on both three-dimensional and two-dimensional data sets and should be applicable to all upcoming galaxy surveys. A proof of principle, using mock catalogues created from N -body simulations, is given.     

H2 in interstellar and extragalactic ices: infrared characteristics, ultraviolet production, and implications

H2 is the most abundant molecule in the universe. We demonstrate that this molecule may be an important component of interstellar and possibly intergalactic ices, both because it can be formed in situ, within the ices, and because gas phase H2 can freeze out onto dust grains in some astrophysical environments. The condensation-sublimation and infrared spectral properties of ices containing H2 are presented. We show that solid H2 in H20-rich ices can be detected by an infrared absorption band at 4137 cm-1 (2.417 micrometers). The surface binding energy of H2 to H2O ice was measured to the delta Hs/k = 555 +/- 35 K. Surface binding energies can be used to calculate the residence times of H2 on grain surfaces as a function of temperature. Some of the implications of these results are considered.     

Determining the cosmological parameters from the linewidths of active galaxies

We have previously shown that the linewidth distribution in AGN can be accounted for by an axisymmetric broad-emission-line region. In this paper we show that the linewidth distribution changes with redshift and that these changes are dependent on H ₀ and q ₀. We show that relatively small samples of AGN at high redshift with measured linewidth at half maximum can be used to distinguish between values of H ₀ and q ₀. Furthermore, larger low-redshift samples can be used to distinguish between luminosity functions and hence different models of quasar evolution.