共查询到20条相似文献，搜索用时 93 毫秒
1.
Barbara Funk Rudolf Dvorak Richard Schwarz 《Celestial Mechanics and Dynamical Astronomy》2013,117(1):41-58
In this investigation we treat a special configuration of two celestial bodies in 1:1 mean motion resonance namely the so-called exchange orbits. There exist—at least—theoretically—two different types: the exchange-a orbits and the exchange-e orbits. The first one is the following: two celestial bodies are in orbit around a central body with almost the same semi-major axes on circular orbits. Because of the relatively small differences in semi-major axes they meet from time to time and exchange their semi-major axes. The inner one then moves outside the other planet and vice versa. The second configuration one is the following: two planets are moving on nearly the same orbit with respect to the semi-major axes, one on a circular orbit and the other one on an eccentric one. During their dynamical evolution they change the characteristics of the orbit, the circular one becomes an elliptic one whereas the elliptic one changes its shape to a circle. This ‘game’ repeats periodically. In this new study we extend the numerical computations for both of these exchange orbits to the three dimensional case and in another extension treat also the problem when these orbits are perturbed from a fourth body. Our results in form of graphs show quite well that for a large variety of initial conditions both configurations are stable and stay in these exchange orbits. 相似文献
2.
S. V. Chernov 《Astronomy Letters》2017,43(3):186-201
We investigate the change in the orbital period of a binary system due to dynamical tides by taking into account the evolution of a main-sequence star. Three stars with masses of one, one and a half, and two solar masses are considered. A star of one solar mass at lifetimes t = 4.57 × 109 yr closely corresponds to our Sun. We show that a planet of one Jupiter mass revolving around a star of one solar mass will fall onto the star in the main-sequence lifetime of the star due to dynamical tides if the initial orbital period of the planet is less than P orb ≈ 2.8 days. Planets of one Jupiter mass with an orbital period P orb ≈ 2 days or shorter will fall onto a star of one and a half and two solar masses in the mainsequence lifetime of the star. 相似文献
3.
Sergei A. Orlov Konstantin V. Kholshevnikov 《Celestial Mechanics and Dynamical Astronomy》2013,116(1):35-52
Dust comnplexes make one of the components of the Solar System. The surface shape of a typical dust complex consisting of particles ejected by a celestial body is found analytically, under reasonable assumptions (the main one being the smallness of perturbations). Parametric equations of the surface are obtained. The main properties of the surface are established and studied. Singular points are found, and the topological type of the surface as a whole and in the vicinity of the singular points (one conic points and one constriction) is examined. 相似文献
4.
Thomas J. Eisler 《Solar physics》1969,7(1):49-53
There is one and only one solution of the viscous solar wind equations which is asymptotically represented for large distances from the sun by a formal solution of Y. C. Whang, C. K. Liu, and C. C. Chang as a power series in the inverse one third power of the distance. 相似文献
5.
本文主要介绍基于科学CCD的低纬子午环数据采集系统的硬件构成及软件设计。为了能绝对而又精确地确定天体的位置 ,低纬子午环需要配备多种精密的测量装置 ,如 :GPS与时钟、 9路Reticon线阵、视频CCD、科学CCD、圆感应同步器、光栅线性位移传感器等。为了能有序地控制并采集这些装置的数据 ,我们设计了一个包含 3个PC机的数据采集与控制系统。文中将描述测量装置的功能 ,然后介绍数据采集方法及软件设计 相似文献
6.
Jin He 《Astrophysics and Space Science》2004,291(2):163-175
Image analysis of over one hundred nearby galaxies (He, 2003) indicates that for any spiral galaxy image of small inclination there is evidence of two orthogonalsets of iso-ratio curves in different scales which, like curvilinear coordinate lines, expand over different galaxy components. This result sets a constraint on galaxy patterns and a general model equation which carries this constraint is given in its geometric form in He (2003). In the current paper the author reformulates the geometric equation into one quasilinearsystem of 3 partial differential equations with 3 dependents (the tangent direction of one set of iso-ratio curves and the two ratio profiles along the two sets of iso-ratio curves respectively). With one profile assumed to be a nonzero constant, there are two dependents and the system of two partial differential equations is a hyperbolic one. The author uses the standard method of characteristics and the boundary condition of ideal arms which are found by setting the above constant to be zero, to solve the hyperbolic system. This provides one analytic method to model galaxy patterns. Its varying parameters will be useful for galacticarm classification and for investigation of galaxy structure. 相似文献
7.
Dragan Slavkov Hajdukovic 《Astrophysics and Space Science》2010,326(1):3-5
I present three relations, striking in their simplicity and fundamental appearance. The first one connects the Compton wavelength of a pion and the dark energy density of the Universe; the second one connects the Compton wavelength of a pion and the mass distribution of non-baryonic dark matter in a galaxy; the third one relates the mass of a pion to fundamental physical constants and cosmological parameters. All these relations are in excellent numerical agreement with observations. 相似文献
8.
The problem of instability arising in a composite system consisting of an infinitely conducting hydromagnetic fluid interacting through gravitational forces with one or more than one neutral gas, is investigated, allowing for a possible relative streaming between the component fluids. Instability criteria are derived for special cases of a two-component (static or relatively streaming) system and for a three-component system consisting of two gases contra-streaming in the presence of a stationary background gas. It is found that for a static system only one unstable mode exists for wave numbers less than a critical value given by the square root of the sum of the squares of the Jeans's wave numbers for individual gases. However, for a configuration, where components are endured with characteristic streaming speeds, there are present simultaneously more than one unstable modes. 相似文献
9.
10.
We present stereoscopic observations of six sequential eruptions of a filament in the active region NOAA 11045 on 2010 Feb 8,with the advantage of the STEREO twin viewpoints in combination with Earth's viewpoint from SOHO instruments and ground-based telescopes.The last one of the six eruptions is a coronal mass ejection,but the others are not.The flare in this successful one is more intense than in the others.Moreover,the velocity of filament material in the successful one is also the largest among them.In... 相似文献
11.
S. V. Chernov 《Astronomy Letters》2017,43(6):429-437
Zahn’s theory of dynamical tides is analyzed critically. We compare the results of this theory with our numerical calculations for stars with a convective core and a radiative envelope and with masses of one and a half and two solar masses. We show that for a binary system consisting of stars of one and a half or two solar masses and a point object with a mass equal to the solar mass and with an orbital period of one day under the assumption of a dense spectrum and moderately rapid dissipation, the evolution time scales of the semimajor axis will be shorter than those in Zahn’s theory by several orders of magnitude. 相似文献
12.
《天文和天体物理学研究(英文版)》2015,(5)
We report the results of a search for variable stars in the open cluster NGC 2141. Ten variable stars are detected, among which nine are new variable stars and they are classified as three short-period W UMa-type eclipsing binaries, two EAtype eclipsing binaries, one EB-type eclipsing binary, one very short-period RS CVntype eclipsing binary, one d-type RR Lyrae variable star, and one unknown type of variable star. The membership and physical properties are discussed, based on their light curves, positions in the color magnitude diagrams, spatial locations and periods.A known EB-type eclipsing binary is also identified as a blue straggler candidate in the cluster. Furthermore, we find that all eclipsing contact binaries have prominent asymmetric eclipses and display the O'Connell effect, which increases with a decrease in orbital periods. This suggests that the O'Connell effect is probably related to the evolution of the orbital period in short period eclipsing binary systems. 相似文献
13.
Przemysław Bartczak Sławomir Breiter Przemysław Jusiel 《Celestial Mechanics and Dynamical Astronomy》2006,96(1):31-48
Simple models of potential based on material points and material segments are confronted with a homogeneous ellipsoid potential.
A spheroid is approximated with a pair of material points or with one material segment. The segment model proves to be more
accurate. For a triaxial ellipsoid, two models are considered: one with five material points and one with two material segments
and a point. When their parameters are determined with the fourth sectorial harmonic ignored, both simple models have a similar
approximation error. Numerical tests indicate that the approximate models of a triaxial ellipsoid are 5 to 10 times faster
than exact formulation, whereas for a spheroid the approximate models are at most twice as fast as the exact formulae. 相似文献
14.
V. L. Afanasiev S. N. Dodonov A. V. Moiseev V. Chavushyan R. Mujica Y. Juarez A. G. Gorshkov V. K. Konnikova M. G. Mingaliev 《Astronomy Letters》2003,29(9):579-586
We present the classification of optical identifications and radio spectra of six radio sources from a complete (in flux density) sample in the declination range 10° to 12°30′ (J2000.0). The observations were carried out with the 6-m Special Astrophysical Observatory telescope (Russia) in the wavelength range 3600–10000 Å, the 2.1-m GHAO telescope (Mexico) in the range 4200–9000 Å, and the RATAN-600 radio telescope in the frequency range 0.97–21.7 GHz. Three of the six objects under study are classified as quasars, one is a BL Lac object, one is an absorption-line radio galaxy, and one is an emission-line radio galaxy. Five objects have flat radio spectra, and one object has a power-law radio spectrum. All of the radio sources identified as quasars or BL Lac objects show variable radio flux densities. The spectra of three objects were separated into extended and compact components. 相似文献
15.
In the five years from June, 1967, to June, 1972, a total of 99 meteorites were found in Roosevelt County, New Mexico and in adjoining Curry County. Of this number, 74 were found by one man. The finds include two achondrites, one pallasite, one carbonaceous chondrite, and 95 chondrites. They appear to represent more than 50 separate meteorite falls. The finding of a large number of meteorites in a small area provides data for an estimate of the probable quantity and average size of the meteorite specimens reaching the earth. The problems involved in allocating a total of 17 available local place names among more than 50 meteorite falls are discussed. 相似文献
16.
Henry E. Kandrup 《Astrophysics and Space Science》1983,97(2):435-452
An exact formula is derived for the average frictional force acting upon a ‘test’ star which moves along a prescribed trajectory amongst a collection of ‘field’ stars which are characterized by a Maxwellian distribution of velocities. In the limit that the actual stellar trajectories may be approximated by their average forms, as determined by the mean gravitational field, one obtains a relatively simple expression which establishes an important connection with the fluctuation-dissipation theorem. For the case of an infinite, homogeneous system, one recovers Chandrasekhar's classical result. Alternatively, by allowing for the possibility of nearly periodic motion, one is led to new and intriguing phenomena. 相似文献
17.
P. Felenbok J. Guérin A. Fernandez V. Cayatte C. Balkowski R.C. Kraan-Korteweg 《Experimental Astronomy》1997,7(2):65-85
We are describing a new multi-fibre positioner, MEFOS, that was in generaluse at the La Silla Observatory, and implemented at the prime focus of theESO 3.6 m telescope. It is an arm positioner using 29 arms in a one degreefield. Each arm is equipped with an individual viewing system for accuratesetting and carries two spectroscopic fibres, one for the astronomical objectand the other one for the sky recording needed for sky subtraction. Thespectral fibres intercept 2.5 arcsec on the sky and run from the prime focusto the Cassegrain, where the B&C spectrograph is located. Afterdescribing the observational procedure, we present the first scientificresults. 相似文献
18.
本文作者用澳大利亚Ｐａｒｋｅｓ６４ｍ射电望远镜观测了ＯＨ１７．７－２．０的拱星ＯＨ脉泽辐射。在观测中共测得了三个峰，其中一个峰是我们新发现的弱源，两个峰是过去发现的强源。用二维Ｇａｕｓｓｉａｎ拟合我们发现强源位置与一个ＩＲＡＳ点源位置相一致，弱源位置在这个ＩＲＡＳ点源位置的西南方。强源的两个峰的速度位置和峰值流量密度都是比较稳定的。 相似文献
19.
Alessandro Morbidelli Antonio Giorgilli 《Celestial Mechanics and Dynamical Astronomy》1993,55(2):131-159
We revisit some results of perturbation theories by a method of successive elimination of harmonics inspired by some ideas of Delaunay. On the one hand, we give a connection between the KAM theorem and the Nekhoroshev theorem. On the other hand, we support in a quantitative fashion a semi-numerical method of analysis of a perturbed system recently introduced by one of the authors. 相似文献
20.
The problem of the attitude dynamics of a triaxial gyrostat under no external torques and one constant internal rotor, is a three degrees-of-freedom system, although thanks to the existence of integrals of motion it can be reduced to only one degree-of-freedom problem. We introduce coordinates to represent the orbits of constant angular momentum as a flow on a sphere. This representation shows that the problem is equivalent to a quadratic Hamiltonian depending on two parameters. We find the exact solution of the orbits in terms of elliptic functions. By making use of properties of elliptic functions we find the solution at each region of the parametric partition from the solution of one region. We also prove that heteroclinic orbits are planar curves. 相似文献