共查询到20条相似文献,搜索用时 31 毫秒
1.
Rodolfo Batista Negri Antonio Fernando Bertachini de Almeida Prado Alexander Sukhanov 《Celestial Mechanics and Dynamical Astronomy》2017,129(3):269-284
The swing-by maneuver is a technique used to change the energy of a spacecraft by using a close approach in a celestial body. This procedure was used many times in real missions. Usually, the first approach to design this type of mission is based on the “patched-conics” model, which splits the maneuver into three “two-body dynamics.” This approach causes an error in the estimation of the energy variations, which depends on the geometry of the maneuver and the system of primaries considered. Therefore, the goal of the present paper is to study the errors caused by this approximation. The comparison of the results are made with the trajectories obtained using the more realistic restricted three-body problem, assumed here to be the “real values” for the maneuver. The results shown here describe the effects of each parameter involved in the swing-by. Some examples using bodies in the solar system are used in this part of the paper. The study is then generalized to cover different mass parameters, and its influence is analyzed to give an idea of the amount of the error expected for a given system of primaries. The results presented here may help in estimating errors in the preliminary mission analysis using the “patched-conics” approach. 相似文献
2.
G. S. Kurbasova 《Bulletin of the Crimean Astrophysical Observatory》2010,106(1):82-86
The appearance of features with cusp points on the diagrams of changes in the coordinates of the Earth’s instantaneous pole
(polhodes) is considered as the result of mapping onto the plane of its displacement over the surface during the Earth’s rotational-translational
motion. The results of qualitative and quantitative analyses of the data on the coordinates of the Earth’s instantaneous pole
are discussed. The basic principles of the theory of Whitney singularities and their application for explaining the bifurcations
of the equilibrium positions for the Zeeman catastrophe machine (Arnold 1990) are used in the analyses. 相似文献
3.
Jun-Liang Zhao Li Chen Zhong-Liang Zu Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 《中国天文和天体物理学报》2006,6(3):287-296
Absolute proper motions and radial velocities of 202 open clusters in the solar neighborhood, which can be used as tracers of the Galactic disk, are used to investigate the kinematics of the Galaxy in the solar vicinity, including the mean heliocentric velocity components (u_1,u_2,u_3) of the open cluster system, the characteristic velocity dispersions (σ_1,σ_2,σ_3), Oort constants (A, B) and the large-scale radial motion parameters (C,D) of the Galaxy. The results derived from the observational data of proper motions and radial velocities of a subgroup of 117 thin disk young open clusters by means of a maximum likelihood algorithm are: (u_1,u2,u3) = (-16.1±1.0, -7.9±1.4,-10.4±1.5) kms~(-1), (σ_1,σ_2,σ_3) = (17.0 ±0.7,12.2±0.9,8.0±1.3) kms~(-1),(A,B) = (14.8±1.0,-13.0±2.7) kms~(-1) kpc~(-1) ,and(C,D) = (1.5±0.7,-1.2±1.5) kms~(-1) kpc~(-1) . A discussion on the results and comparisons with what was obtained by other authors is given. 相似文献
4.
Shuang Gao Bi-Wei Jiang Yong-Heng Zhao Department of Astronomy Beijing Normal University Beijing National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2007,7(1):111-119
1 INTRODUCTION The globular cluster (GC hereafter), as the oldest star group in the universe, has been a target that astro- physics has paid close attention to all the time. The near-field (Galaxy) cosmology makes contacts with the far-field cosmology by … 相似文献
5.
Y. P. Varshni 《Astrophysics and Space Science》1988,149(2):197-215
The emission and absorption lines (3716–4290) in the spectrum of the quasar 0237–233 are identified within the framework of the PLS model. The available evidence indicates that it is a helium star. Similarities between the spectral properties of 0237–233 and the star Upsilon Sagittarii are pointed out. Predictions are made for the absorption-line spectrum which falls outside 3716–4290 and also for an expected discontinuity at 2600. 相似文献
6.
Ying-Chun Wei Xin-Ji Wu Qiu-He Peng Na Wang Jin Zhang National Astronomical Observatories/Urumqi Observatory Chinese Academy of Sciences Urumqi Department of Astronomy Peking University Beijing Department of Astronomy Nanjing University Nanjing 《中国天文和天体物理学报》2005,5(6):610-618
Based on the undisturbed, finite thickness disk gravitational potential, we carried out 3-D Monte Carlo simulations of normal pulsars. We find that their scale height evolves in a similar way for different velocity dispersions (σv): it first increases linearly with time, reaches a peak, then gradually decreases, and finally approaches a stable asymptotic value. The initial velocity dispersion has a very large influence on the scale height. The time evolution of the scale height is studied. When the magnetic decay age is used as the time variable, the observed scale height has a similar trend as the simulated results in the linear stage, from which we derive velocity dispersions in the range 70- 178km s-1, which are near the statistical result of 90 - 270km s-1 for 92 pulsars with known transverse velocities. If the characteristic age is used as the time variable, then the observed and theoretical curves roughly agree for t > 108 yr only if σv < 25km s-1. 相似文献
7.
To correctly determine the relative contribution of aerosol to the scattering properties of a gas–aerosol medium in the continuum, we propose a method that allows more reliable values of the imaginary part of the refractive index n i to be obtained for Jupiter’s atmosphere in the short-wavelength spectral range. We considered the measurement data on the spectral values of the geometric albedo of Jupiter acquired in 1993 and used the model of homogeneous spherical aerosol particles. The obtained values of n i are 0.00378, 0.00309, 0.00254, 0.00175, 0.00123, 0.00084, 0.00064, 0.00045, 0.00031, 0.00033, 0.00013, and 0.00008 at wavelengths λ = 320, 350, 375, 400, 420, 450, 470, 500, 520, 550, 606, and 631 nm, respectively. 相似文献
8.
Liu Yong-Zhen 《Astrophysics and Space Science》1989,152(2):191-201
From the characteristic actions
(s), we can derive various relations between the basic characteristic quantities of objects and the fundamental constants in known physical laws. The main physical processes which lead to the formation of objects should be included in some such reletions through the fundamental constants. The problem of the origin of galaxies has been considered on the basis of the theory of actions
(s). It has been shown that in addition to gravitational effect, the dissipation process of the adiabatic density perturbations arising from the Thomson scattering in the early universe is a crucial process in forming galaxies; and if the Hubble constant has a valueH
0 50 km s–1 Mpc–1, the protogalaxies might be formed just before recombination. 相似文献
9.
Jia-Long Wang National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2006,(3)
Taking the 13-point smoothed monthly sunspot number, Ri, and the deviation of the 13 associated monthly sunspot numbers from the smoothed one, D_i, as a number-pair describing the global level of sunspot activity, the evolution of the level is statistically studied for the period from the month which is just 48 months before the minimum to the minimum in the descending phase, using the observed data of Solar Cycles 10 to 22. Our results show (1) for 46 months (94%) of the studied 49 months it is found that for a given month, the distribution of the 13 pairs which come from the 13 solar cycles on a log Ri-D_i plane may be fitted by a straight line with a correlation coefficient larger than the critical one at confidence level α= 5%, and for 36 months (73%) the fitting is even better, for α= 1%;(2) time variations of these two parameters and their correlations in the studied period can be described respectively by functions of time, whose main trends may be expressed by a linear or simple curvilinear function; (3) the evolutionary path of the level of sunspot activity may be represented by a logarithmic function as log R_i=0.704 In D_i-0.291. 相似文献
10.
11.
Some results of observations of the spectrum of the spectroscopic-binary Ap star CrB in the region of the lithium line Li I 6708Å are presented. The observations were made at the Crimean Astrophysical Observatory over the period 1993–1995 with the coudé spectrograph equipped with a CCD camera on the 2.6-m telescope. Several factors which can affect the behavior of the lithium blend are examined: stellar rotation, magnetic field, isotopic shift, the binary system, and blending by unidentified elements. The principal result of this work is the detection of variability of the lithium blend Li I 6708Å over the period of rotation of the star. The variations of the radial velocity Vr, and the FWHM of the lithium blend are reported here for the first time. They indicate either a nonuniform distribution of lithium or a nonuniform distribution of conditions for excitation of the lithium resonance doublet in the complex structure of the strong surface magnetic field. Similar variations are also shown by the lines of the rare-earth elements Gd II 6702.10 Å, Gd II + Ce II 6704.3Å, and Ce II + Fe I 6706.0 Å.Translated fromAstrofizika, Vol. 39, No. 1, pp. 19–30, January–March, 1996. 相似文献
12.
High-resolution (0.1-Å) spectra of the 6815-Å band of methane are presented for Jupiter, Saturn, Uranus, and Neptune. Spectra for Uranus, Neptune, and the equatorial region of Saturn were acquired with the SPIFI (W. H. Smith, T. R. Hicks, and J. P. Born (1978). Proceedings of the 4th International Colloquium on Astrophysics, Triest, July 3–7, 1978. pp. 593–599) at the 2.2-m telescope of the Mauna Kea Observatory during May and June 1980. Additional spectra were obtained for Jupiter and the northern temperate and polar regions of Saturn in December 1980 and January 1981 from Kitt Peak National Observatory's McMath Solar Telescope. The spectra show a dichotomy in strength of methane absorption between Jupiter-Saturn and Uranus-Neptune. A simple model analysis, based on homogeneous scattering models, is unable to resolve whether this dichotomy is due to an actual increase in the methane mixing ratio with solar distance or to the temperature dependence of line strengths and absorption pathlengths in these atmospheres. If the rotational quantum number for the prominent 6818.9-Å feature is J < 4, then significant aerosol extinction must exist within the visibly accessible portion of Uranus' atmosphere for the methane mixing ratio to be greater than the solar value. 相似文献
13.
We present the results of our long-term U BV R observations of the star T Tauri performed at Mt. Maidanak Observatory from 1986 until 2003. These data, together with previous photoelectric observations of other authors, suggest that the long-term variations of the light curve are not periodic, but have a cycle with a time scale of 6–9 yr. The light curve also exhibits slower variations with time scales of ~30–40 yr. We confirm the existence of periodic brightness variations with a period of \(P = 2\mathop .\limits^d 798\) over many years; this process is peculiar in that the phase and shape of the phase curve change from season to season. We analyze the color behavior of the star. We found evidence of a strong flare occurred on October 5, 1999, when the brightness of the star reached \(9\mathop .\limits^m 22\). This is the strongest flare recorded during its photoelectric observations. 相似文献
14.
1 INTRODUCTION Gan, Li and Chang (2001a) proposed a quantitative method to obtain the lower energycutoff (Er) of power-law electrons from the observed broken-down double power-law hard Xray spectrum. Most recently Can et al. (2002) improved the method and let it be moreself-consistent. They applied their improved method to the 54 hard X-ray events observed withBATSE/CGRO and acquired more general results in comparison with those obtained by Canet al. (2001b). Despite the data is rel… 相似文献
15.
S. G. Sergeev 《Astrophysics and Space Science》1992,197(1):77-86
A great number of spectra of the Seyfert galaxy nucleus NGC 4151 were obtained in the Crimean Astrophysical Observatory in 1988–1990 using the CCD. Significant variation in continuum intensity and broad H line profile were noted. Differences between individual spectra and the spectrum taken as a standard were calculated to study this variability. It was noted that different parts of the profile are varying in different ways. Smaller changes are located at far-away regions of the wings and at the low positive velocities of the profile. Lower variations in the red part of H profile near the center of the line are interpreted by the delay effect in an expanded shell. Since the evidences for accretion in a BIR are clisting (including NGC 4151) then either the BLR is a complex system where both inflow and low velocities outflow are observed or the outflow must be referred to the inner NLR. Cross correlation analysis shows shorter delay for the higher velocities of the H profile and does not contradict to the outflow at low velocities (near the line center), but its confidence level is small. Lower response to the continuum changes at far away parts of the broad H wings evidences that the gas in the vicinity of the central engine is optically thin for the ionizing radiation. 相似文献
16.
Dramatic extensions of experimental possibilities (spacecraft RHESSI, CORONAS-F and others) in solar gamma-ray astronomy call for urgent, detailed theoretical consideration of a set of physical problems of solar activity and solar-terrestrial relationships that earlier may have only been outlined. Here we undertake a theoretical analysis of issues related to the production of gamma-radiation in the processes of interactions of energetic (accelerated) heavy and middle nuclei with the nuclei of the solar atmosphere (the so-called i-j interactions). We also make an estimate of the contribution of these interactions to the formation of nuclear and isotopic abundances of the solar atmosphere in the range of light and rare elements. The analysis is carried out for solar flares in the wide range of their intensities. We compare our theoretical estimates with RHESSI observations for the flare of 2002 July 23. It was shown that the 24Mg gamma-ray emission in this event was produced by the newly generated Mg nucle 相似文献
17.
G. N. Kichigin 《Astronomy Letters》2009,35(4):261-269
We consider the processes related to the formation of the so-called foreshock region upstream of the Earth’s bow shock. We suggest a model based on the surfing of pick-up ions in the bow shock front in terms of which the ion acceleration mechanism in the front can be explained. We ascertain the physical conditions under which the accelerated ions lie upstream of the shock front and determine the direction of motion of the energetic ions. We conclude that it is this population of energetic ions (longitudinal beams) that plays a major role in forming the ion foreshock boundary. 相似文献
18.
Zhen-Yu Wu Jia-Ji Wang Li ChenShanghai Astronomical Observatory Chinese Academy of Sciences Shanghai National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2002,2(3):216-225
We examine 14 plates of the globular cluster M3 (NGC 5272) taken with the 40 cm refractor at the Sheshan station of Shanghai Astronomical Observatory. The plates span over a period of about 77 years. The positions and absolute proper motions of eight stars in the Hipparcos Catalogue and of 49 stars in the Tycho-2 Catalogue are used as the reference frame. The astrometric reduction is made with the central overlapping principle. The absolute proper motions of 534 stars in a region of about 100' × 100' around the cluster are measured. With the new proper motion data the membership probabilities of the stars are determined. The average absolute proper motion obtained for the cluster is -0.06@0.30 mas yr-1 in R.A. and -2.6@0.30 mas yr-1 in Decl. By combining this result with the known distance and radial velocity of the cluster, we also obtained the Galactic orbit of M3 for a chosen three-component Galactic potential. 相似文献
19.
Recently, a tachyonic field was presented as a dark energy model to represent the present acceleration of the Universe. In this paper, we consider a mixture of tachyonic fluid with a perfect fluid. For this purpose we consider barotropic fluid and Generalized Chaplygin gas (GCG). We present a particular form of the scale factor. We solve the equations of motion to get exact solutions of the density, tachyonic potential and the tachyonic field. We introduce a coupling term to show that the interaction decays with time. We also show that the nature of the potentials vary, so the interaction term reduces the potential in both cases. 相似文献
20.
It is suggested that gravitationally bound systems in the Universe can be characterized by a set of actions ?(s). The actions $$\hbar ^{\left( s \right)} = \left( {{\hbar \mathord{\left/ {\vphantom {\hbar {\frac{1}{{2\pi }}\frac{{C^5 }}{{GH_0^2 }}}}} \right. \kern-\nulldelimiterspace} {\frac{1}{{2\pi }}\frac{{C^5 }}{{GH_0^2 }}}}} \right)^{s/6} \left( {\frac{1}{{2\pi }}\frac{{C^5 }}{{GH_0^2 }}} \right)$$ ,derived from general theoretical consideration, are only determined by the fundamental physical constants (Planck's action ?, the velocity of lightC, gravitational constantG, and Hubble's constantH 0) and a scale parameters. It is shown thats=1, 2, and 3 correspond, respectively, to the scales of galaxies, stars, and larger asteroids. The spectra of the characteristic angular momenta and masses for gravitationally bound systems in the Universe are estimated byJ (s) andM (s) =(? (s) Cα/G)1/2. Taken together, an angular momentum-mass relation is obtained,J (s)=A(M(s))2, where \(A = G/C\alpha ,{\text{ }}\alpha \simeq \tfrac{{\text{1}}}{{{\text{137}}}}\) , for the astronomical systems observed on every scale. ThisJ-M relation is consistent with Brosche's empirical relation (Brosche, 1974). 相似文献