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1.
D. V. Nikonchuk 《Astronomy Letters》2012,38(12):813-828
Anonlinear analytical theory of secular perturbations in the problem of the motion of a systemof small bodies around a major attractive center has been developed. Themutual perturbations of the satellites and the influence of the oblateness of the central body are taken into account in the model. In contrast to the classical Laplace-Lagrange theory based on linear equations for Lagrange elements, the third-degree terms in orbital eccentricities and inclinations are taken into account in the equations. The corresponding improvement of the solution turns out to be essential in studying the evolution of orbits over long time intervals. A program inC has been written to calculate the corrections to the fundamental frequencies of the solution and the third-degree secular perturbations in orbital eccentricities and inclinations. The proposed method has been applied to investigate the motion of the major Uranian satellites. Over time intervals longer than 100 years, allowance for the nonlinear terms in the equations is shown to give corrections to the coordinates of Miranda on the order of the orbital eccentricity, which is several thousand kilometers in linear measure. For other satellites, the effect of allowance for the nonlinear terms turns out to be smaller. Obviously, when a general analytical theory of motion for the major Uranian satellites is constructed, the nonlinear terms in the equations for the secular perturbations should be taken into account. 相似文献
2.
In the text-books of astronomy, sections generally related to the Moon deal with the orbital elements of the Earth-Moon system such asa, e, i, ,
and the time of perigee passage. While the MEAN of the first of the three elements do not vary, mean longitude of the ascending node-mean longitude of the lunar perigee and the time of perigee passage undergoes secular as well as periodic changes due predominantly to the action of the Sun's gravitational attraction. While to a certain degree, explanations related to the calculation of the lunar orbit parameters are given, not a single graphical representation of these short- or long-periodic changes are presented. We allow the number of data related to these periodic changes must cover a large span of time; and if regression of the line of nodes or advances of the line of apses are to be graphically seen, data covering 18.61 and 8.85 yr, respectively, are needed. In this work we particularly aim at the graphical representation of the periodic changes of the line of nodes. 相似文献
3.
T. P. Kiseleva S. M. Chanturiya T. A. Vasil’eva O. A. Kalinichenko 《Solar System Research》2012,46(5):387-389
The sets of photographic observations of the Galilean satellites of Jupiter taken at the Abastumani Astrophysical Observatory of the Academy of Sciences of Georgia are analyzed here. Positional observations of the system of Jupiter were made in the period from 1985 to 1994 with the use of the double Zeiss astrograph in order to determine the exact coordinates of Jupiter and its satellites. The accurate positions of the satellites and Jupiter itself, as well as their stellar (equatorial) coordinates relative to the stars of the currently available catalogs and the relative ??satellite ?? satellite?? coordinates were obtained from the observations. From the comparison of the observation results with the modern theories of motion of satellites, the accuracy in determining the positions of the satellites and Jupiter was analyzed. The results of observations are presented in the Pulkovo database of observations of Solar System bodies that is accessible to users at http://www.puldb.ru. 相似文献
4.
A. Vienne 《Planetary and Space Science》2008,56(14):1797-1803
Recently the motion of the main satellites of Jupiter, Saturn and Uranus have been modelled in order to get accurate ephemerides. These models have been fitted over a large amount of observations. Among these ones, the positions issued from the observations of mutual events are the most accurate. We can then expect to obtain a new kind of dynamical informations directly linked to planetological questions. We have to determine what information is used in these observations to get the still unknown dynamical parameters. We look after these questions especially in the Jovian and Saturnian systems. 相似文献
5.
G. I. Shirmin 《Celestial Mechanics and Dynamical Astronomy》1974,9(2):183-190
The analysis of regions of convergence of expansions of the right-hand sides of the differential equations of motion in the vicinity of the collinear libration points in the circular restricted three-body problem in powers of coordinates of the infinitesimal body due to F. R. Moulton (Moulton, 1920) is shown to be erroneous and his results are corrected. The generalisation of Moulton's results to analogous expansions of the equations in the elliptic problem of three bodies made by R. W. Farquhar (Farquhar, 1968) is shown to be groundless. 相似文献
6.
K. G. Miesserov 《Earth, Moon, and Planets》1982,27(1):13-25
The formation of the solar system is considered from the physico-chemical point of view. The main role in the process is ascribed to heavy metals and to the surface tension that had arisen as a result of appearance of a liquid layer of fused substance in the equatorial region of the protostar. The formation of the liquid layer was caused by the transfer of fused substance droplets under the action of centrifugal forces in the direction of the protostar surface. Due to the surface tension the prevalence of the centrifugal forces over the gravitational ones was able to reach the value when the density differentiation of the substance began to take place under the effect of the centrifugal forces, and accumulation of heavy metals proceeded in outermost equatorial region of the protostar. As a result the disk has been formed and a liquid ring was separated from the protostar. Later explosions on the young Sun sent parts of the hardened ring which possessed the first cosmic velocity to different distances away from the Sun. In such a way planets, their satellites, asteroids, meteorites and comets were formed. The physical characteristics of planets, the parameters of their orbits, and the data on the structure of meteorites are consistent with ideas developed in the paper. 相似文献
7.
P. A. Evans A. P. Beardmore K. L. Page J. P. Osborne P. T. O'Brien R. Willingale R. L. C. Starling D. N. Burrows O. Godet L. Vetere J. Racusin M. R. Goad K. Wiersema L. Angelini M. Capalbi G. Chincarini N. Gehrels J. A. Kennea R. Margutti D. C. Morris C. J. Mountford C. Pagani M. Perri P. Romano N. Tanvir 《Monthly notices of the Royal Astronomical Society》2009,397(3):1177-1201
We present a homogeneous X-ray analysis of all 318 gamma-ray bursts detected by the X-ray telescope (XRT) on the Swift satellite up to 2008 July 23; this represents the largest sample of X-ray GRB data published to date. In Sections 2–3 , we detail the methods which the Swift -XRT team has developed to produce the enhanced positions, light curves, hardness ratios and spectra presented in this paper. Software using these methods continues to create such products for all new GRBs observed by the Swift -XRT. We also detail web-based tools allowing users to create these products for any object observed by the XRT, not just GRBs. In Sections 4–6 , we present the results of our analysis of GRBs, including probability distribution functions of the temporal and spectral properties of the sample. We demonstrate evidence for a consistent underlying behaviour which can produce a range of light-curve morphologies, and attempt to interpret this behaviour in the framework of external forward shock emission. We find several difficulties, in particular that reconciliation of our data with the forward shock model requires energy injection to continue for days to weeks. 相似文献
8.
Review of concepts of stability 总被引：1，自引：0，他引：1
Victor Szebehely 《Celestial Mechanics and Dynamical Astronomy》1984,34(1-4):49-64
9.
We suggest a model to consistently describe the available experimental data on the elemental cosmic-ray energy spectra obtained in direct measurements and to make a smooth transition to the spectrum of all particles measured with extensive air showers. The model suggests the existence of three classes of cosmic-ray sources—shocks from supernova explosions that produce power-law rigidity spectra with different maximum rigidities and different spectral indices. The shocks from high-mass supernovae exploding in OB associations are assumed to be the most powerful class of sources. This class of sources accelerates cosmic rays to a maximum rigidity of 4 × 1015 V. The shocks from nonassociated supernovae exploding into a random interstellar medium are assumed to be the next class (in order of decreasing power). This class of sources accelerates cosmic rays to a maximum rigidity of 5 × 1013 V. The third, weakest class of sources is assumed to accelerate cosmic rays to a maximum rigidity of 2 × 1011 V. Nova explosions could be possible physical objects in this class. 相似文献
10.
N. Yu. Lovyagin 《Astrophysical Bulletin》2009,64(3):217-228
The methods of determining the fractal dimension and irregularity scale in simulated galaxy catalogs and the application of these methods to the data of the 2dF and 6dF catalogs are analyzed. Correlation methods are shown to be correctly applicable to fractal structures only at the scale lengths from several average distances between the galaxies, and up to (10 ? 20)% of the radius of the largest sphere that fits completely inside the sample domain. Earlier the correlation methods were believed to be applicable up to the entire radius of the sphere and the researchers did not take the above restriction into account while finding the scale length corresponding to the transition to a uniform distribution. When an empirical formula is applied for approximating the radial distributions in the samples confined by the limiting apparent magnitude, the deviation of the true radial distribution from the approximating formula (but not the parameters of the best approximation) correlate with fractal dimension. An analysis of the 2dF catalog yields a fractal dimension of 2.20 ± 0.25 on scale lengths from 2 to 20 Mpc, whereas no conclusive estimates can be derived by applying the conditional density method for larger scales due to the inherent biases of the method. An analysis of the radial distributions of galaxies in the 2dF and 6dF catalogs revealed significant irregularities on scale lengths of up to 70 Mpc. The magnitudes and sizes of these irregularities are consistent with the fractal dimension estimate of D =2.1–2.4. 相似文献
11.
Magnetars are the neutron stars with the highest magnetic fields up to 1015–1016 G. It has been proposed that they are also responsible for a variety of extra-galactic phenomena, ranging from giant flares in nearby galaxies to fast radio bursts. Utilizing a relativistic mean field model and a variable magnetic field configuration, we investigate the effects of strong magnetic fields on the equation of state and anisotropy of pressure of magnetars. It is found that the mass and radius of low-mass magnetars are weakly enhanced under the action of the strong magnetic field, and the anisotropy of pressure can be ignored. Unlike other previous investigations, the magnetic field is unable to violate the mass limit of the neutron stars. 相似文献
12.
According to the conservation principle of angular momentum, we calculate in this paper the revolution period and the distance between the Earth and the Moon in the equilibrium state of the tidal evolution in the Earth-Moon system. The difference of energy between the current state and the equilibrium state is used to compute the time needed to fulfil the equilibrium state. Then the long-term variations of the Earth-Moon distance and of the Earth rotation rate are further estimated. 相似文献
13.
In previous publications the author considered how breaking buoyancy waves and the thermal source arising due to different absorption coefficients of solar and atmospheric radiation fluxes contributed to turbulence. In this study, the contribution to turbulence made by the dynamical source arising in consequence of convective instability of large-scale atmospheric motions is examined. Its value is estimated from experimental wind speed data for the atmosphere of Venus. The contributions of the indicated sources of turbulent energy are compared. The rate of dissipation of kinetic energy due to molecular viscosity is demonstrated to be several orders of magnitude less than the rate of dissipation necessary to maintain an invariable superrotation pattern. This is an additional argument for the permanent existence of turbulence in the atmosphere of Venus, which many authors consider doubtful. It is demonstrated why turbulence is present at the atmospheric stratification that seems to be stable. 相似文献
14.
A hypothesis is proposed for the mechanism of superrotation of the atmosphere of Venus involving the following processes. Winds near the planet's surface, making up part of the Hadley cell, flow past the surface relief and excite internal atmospheric gravity waves. While moving upward, these waves become unstable and collapse generating turbulent eddies. Some portion of the energy of these eddies is transferred to a two-dimensional flow, which is maintained also at the expense of instability of large-scale motions. In this flow, the inverse energy cascade (transition from smaller eddies to larger eddies), or negative viscosity, appears as a key element of this mechanism. Large-scale quasi-two-dimensional turbulent eddies transfer their energy to Rossby planetary waves which, in turn, transmit it to a zonal flow. Based on this hypothesis and the existing experimental data, the time period over which superrotation is established, as well as the vertical and horizontal eddy viscosity coefficients, is estimated. In parallel, arguments in favor of the proposed hypothesis are obtained. 相似文献
15.
Vittorio Banfi 《Earth, Moon, and Planets》1986,36(1):1-10
A theoretical model, based on simple and fundamental concepts of classical mechanics, is presented. It describes the possible historical evolution of the inclination angles of the planetary axes of rotation, with respect to the normal to orbital planes. Owing to the model structure, reasonable agreement with observational facts is expected, especially for the outer and giant planets. 相似文献
16.
《Chinese Astronomy and Astrophysics》2007,31(2):211-220
The space geodetic technology requires an accurate model of correction of refraction delay by the neutral atmosphere that varies from one observing station to another, and from one azimuth to the next. It is pointed out that under the present condition the astronomical refraction can not yet be directly determined, any correction model because of its high dependence on the assumed atmospheric distribution, is incapable of achieving the required accuracy or of improving the cut-off altitude. In this paper, based on the special properties of the lower latitude meridian circle at Yunnan Observatory and our experience of determining atmospheric refraction therewith, a new method is proposed for improving the accuracy of refraction delay correction. Namely, the measured data of astronomical refraction of an observing station from near zenith to low altitudes in different azimuths are used to evaluate the refractivities and the parameters of the mapping functions, thereby establishing a model of atmospheric refraction delay correction that varies with the observing station and the azimuth. Since it is unnecessary for the new method to adopt any atmospheric distribution model, application of this new method will improve correction accuracy of refraction delay to better than 1mm at zenith and to centimeters at low altitudes, and improve the cut-off altitude to below 5 degrees. 相似文献
17.
D. Sher 《Astrophysics and Space Science》1970,6(2):275-286
The potential energy of clusters of stars in which the distribution of matter is taken to be continuous is compared with that of static model clusters in which the distribution of matter is discrete, the comparison being made from the point of view of applying the virial theorem to estimate the masses of the clusters. There is good agreement on the average between the two cases as long as the stellar distribution is random. Systematic differences occur whenever there is any departure from randomness. However, reduction of the mass of a cluster as estimated by means of the virial theorem by even as much as a factor of 2 on the average would seem to require even greater departures from randomness in the stellar distribution than are considered here. As might be expected there are sometimes very large fluctuations in the potential energy from one cluster to the next in the discrete case.Contributions of the Louisiana State University Observatory, No. 30. 相似文献
18.
Exact formulas are derived for calculating the correction for phase to the central meridian longitude and the latitude of the center of the illuminated part of the visible disk of a spherical planet in projection onto the plane of the sky. The range of possible values of the phase correction to the central meridian longitude is determined. The proposed formulas are valid for any planet's orientation with respect to the Earth and Sun and allow a transition, in planetocentric coordinates, from the center of the geometric disk of a spherical planet to the center of the illuminated part of the planet's visible disk. The reduction formulas are derived for direct and inverse transitions between the two aforementioned points of the planetary disk in geocentric equatorial coordinates. The examples of special cases of illumination of visible disks of planets in specific ephemeris are given. 相似文献
19.
The literal solution of the restricted three body problem obtained by the authors up to the eleventh order with respect to the minor parameter is applied to the investigation of the motion of Phoebe, the ninth satellite of Saturn. As distinct from the existing analytical theories of the motion of the satellite, in the present paper the planetary perturbations are taken into account. A comparison with the modern numerical theory of the motion of Phoebe has shown that the new analytical theory of the satellite motion represents observations with the same degree of accuracy. 相似文献
20.
The HI content of galaxies in the Eridanus group is studied using the GMRT observations and the HIPASS data. A significant
HI deficiency up to a factor of 2–3 is observed in galaxies in the high galaxy density regions. The HI deficiency in galaxies
is observed to be directly correlated to the local projected galaxy density, and inversely correlated to the line-of-sight
radial velocity. Furthermore, galaxies with larger optical diameters are predominantly in the lower galaxy density regions.
It is suggested that the HI deficiency in Eridanus is due to tidal interactions. In some galaxies, evidences of tidal interactions
are seen. An important implication is that significant evolution of galaxies can take place in the group environment. In the
hierarchical way of formation of clusters via mergers of groups, a fraction of the observed HI deficiency in clusters could
have originated in groups. The co-existence of S0s and severely HI deficient galaxies in the Eridanus group suggests that
tidal interaction is likely to be an effective mechanism for transforming spirals to S0s. 相似文献