共查询到20条相似文献，搜索用时 156 毫秒
1.
N. V. Ardeljan G. S. Bisnovatyi-Kogan S. G. Moiseenko 《Astrophysics and Space Science》1996,239(1):1-13
All the families of planar symmetric simple-periodic orbits of the photogravitational restricted plane circular three-body problem, are determined numerically in the case when the primaries are of equal mass and radiate with equal radiation factors (q
1=q2=q). We obtain a global view of the possible patterns of periodic three-body motion while the full range of values of the common radiation factor is explored, from the gravitational case (q=1) down to near the critical value at which the triangular equilibria disappear by coalescing with the inner equilibrium pointL
1 on the rotating axis of the primaries. It is found that for large deviations of its value from the gravitational case the radiation factorq can have a strong effect on the structure of the families. 相似文献
2.
Lennard F. Bakker Tiancheng Ouyang Duokui Yan Skyler Simmons 《Celestial Mechanics and Dynamical Astronomy》2011,110(3):271-290
We analytically prove the existence of a symmetric periodic simultaneous binary collision orbit in a regularized planar pairwise
symmetric equal mass four-body problem. This is an extension of our previous proof of the analytic existence of a symmetric
periodic simultaneous binary collision orbit in a regularized planar fully symmetric equal mass four-body problem. We then
use a continuation method to numerically find symmetric periodic simultaneous binary collision orbits in a regularized planar
pairwise symmetric 1, m, 1, m four-body problem for m between 0 and 1. Numerical estimates of the the characteristic multipliers show that these periodic orbits are linearly stability
when 0.54 ≤ m ≤ 1, and are linearly unstable when 0 < m ≤ 0.53. 相似文献
3.
D. Viswanath 《Celestial Mechanics and Dynamical Astronomy》2006,94(2):213-235
The restricted three-body problem describes the motion of a massless particle under the influence of two primaries of masses
1− μ and μ that circle each other with period equal to 2π. For small μ, a resonant periodic motion of the massless particle
in the rotating frame can be described by relatively prime integers p and q, if its period around the heavier primary is approximately 2π p/q, and by its approximate eccentricity e. We give a method for the formal development of the stable and unstable manifolds associated with these resonant motions.
We prove the validity of this formal development and the existence of homoclinic points in the resonant region. In the study
of the Kirkwood gaps in the asteroid belt, the separatrices of the averaged equations of the restricted three-body problem
are commonly used to derive analytical approximations to the boundaries of the resonances. We use the unaveraged equations
to find values of asteroid eccentricity below which these approximations will not hold for the Kirkwood gaps with q/p equal to 2/1, 7/3, 5/2, 3/1, and 4/1. Another application is to the existence of asymmetric librations in the exterior resonances.
We give values of asteroid eccentricity below which asymmetric librations will not exist for the 1/7, 1/6, 1/5, 1/4, 1/3,
and 1/2 resonances for any μ however small. But if the eccentricity exceeds these thresholds, asymmetric librations will exist
for μ small enough in the unaveraged restricted three-body problem. 相似文献
4.
We have treated formation of spectral lines in a commoving frame where photoionization is predominant over collisional processes.
We have assumed that the radiation field for causing photoionization is a function of Planck function. We have also considered
the situation in which the continuum contributes to the radiation in the line. In all the models the quantityB/A (ratio of outer to inner radii) is kept equal to 10 and the total optical depth is taken to be 103. The velocity is assumed to be varying according to the lawdV/dτ ∼ < 1/τ whereτ is the optical depth (τ > 0) in the given shell. The velocities at the innermost radius (r =A) are set equal to 0 and at the outermost radius (r =B), the maximum velocities are taken to be 0, 1, 3 and 10 Doppler units. The calculated line profiles are those seen by an observer
at infinity.P Cygni-type profiles are observed in the case of a medium with no continuum absorption. For a medium with continuum absorption
double peaked asymmetric profiles are noticed when the velocities are small; the two emission peaks merge into a single asymmetric
peak for larger velocities. 相似文献
5.
We investigate the Cassini's laws which describe the rotational motion in a 1:1 spin-orbit resonance. When this rotational motion follows the conventional Cassini's laws, the figure axis coincides with the angular momentum axis. In this case we underline the differences between the rotational Hamiltonian for a 'slow rotating' body like the Moon and for a 'fast rotating' body like Phobos. Then, we study a more realistic rotational Hamiltonian where the angle J between the figure axis and the angular momentum axis could be different from zero. This Hamiltonian has not been studied before. We have found a new particular solution for this Hamiltonian which could be seen as an extension of the Cassini's laws. In this new solution the angle J is constant, which is not zero, and the precession of the angular momentum plane is equal to the mean motion of the argument of pericenter of the rotating body. This type of rotational motion is only possible when the orbital eccentricity of the rotating body is not zero. This new law enables describing in particular, the Moon mean rotational motion for which the mean value of the angle J is found to be equal to 103.9±0.7 s of arc. 相似文献
6.
Josefina Casasayas Jaume Llibre Ana Nunes 《Celestial Mechanics and Dynamical Astronomy》1994,60(2):273-288
In this paper, we give a new derivation of the equations for the central configurations of the 1+n body problem. In the case of equal masses, we show that forn large enough there exists only one solution. Our lower bound forn improves by several orders of magnitude the one previously found by Hall. 相似文献
7.
V. A. Sheminova 《Solar physics》2009,254(1):29-50
The properties of solar magnetic fields on scales less than the spatial resolution of solar telescopes are studied. A synthetic
infrared spectropolarimetric diagnostic based on a 2D MHD simulation of magnetoconvection is used for this. Analyzed are two
time sequences of snapshots that likely represent two regions of the network fields with their immediate surroundings on the
solar surface with unsigned magnetic flux densities of 300 and 140 G. In the first region from the probability density functions
of the magnetic field strength it is found that the most probable field strength at log τ
5=0 is equal to 250 G. Weak fields (B<500 G) occupy about 70% of the surface, whereas stronger fields (B>1000 G) occupy only 9.7% of the surface. The magnetic flux is −28 G and its imbalance is −0.04. In the second region, these
parameters are correspondingly equal to 150 G, 93.3%, 0.3%, −40 G, and −0.10. The distribution of line-of-sight velocities
on the surface of log τ
5=−1 is estimated. The mean velocity is equal to 0.4 km s−1 in the first simulated region. The average velocity in the granules is −1.2 km s−1 and in the intergranules it is 2.5 km s−1. In the second region, the corresponding values of the mean velocities are equal to 0, −1.8, and 1.5 km s−1. In addition the asymmetry of synthetic Stokes V profiles of the Fe i 1564.8 nm line is analyzed. The mean values of the amplitude and area asymmetry do not exceed 1%. The spatially smoothed
amplitude asymmetry is increased to 10% whereas the area asymmetry is only slightly varied. 相似文献
8.
Series of photometric and colorimetric observations of the Main-Belt asteroid 423 Diotima during its five oppositions were obtained at the Crimean Astrophysical Observatory. It was concluded, based on the results of a frequency analysis of the V-band photometry obtained in 1990, that the asteroid is a binary system: the rotation period of the primary component is equal to 4.
h56, and the period of rotation and the orbital period of the satellite are equal to 14.
h90. An analysis of simultaneous BV and BVR observations made in 1993 and 1998–1999 yielded a rotation period of 4.
h54 ± 0.
h01 for the primary component. An analysis of the sets of V-band observations of the asteroid made from 1982 through 2000 allowed us to find the period of forced precession, which was equal to 113d (or 226d). It was suggested that the axis of the primary component of the binary asteroid precesses and the large amplitude of brightness variations (about 1
m
) is due to its lenticular shape. 相似文献
9.
We present velocity observations, obtained with the E. W. Fick Observatory 0.6 m telescope, of the 7th magnitudeK1 star HR 7112. Our observations show that HR 7112 is a double-line spectroscopic binary system composed of almost equal mass
stars with a period of 215.6 days. The orbit has an eccentricitye = 0.142 and the stars orbit each other with a mean semi-major axis distance of approximately 0.4sin(i) AU. The masses of
the stars are consistent with the classification as giant stars. Tidal effects are known to circularise the orbits of giant
stars and this process is apparently underway in this system. 相似文献
10.
The existence of new equilibrium points is established in the restricted three-body problem with equal prolate primaries.
These are located on the Z-axis above and below the inner Eulerian equilibrium point L
1 and give rise to a new type of straight-line periodic oscillations, different from the well known Sitnikov motions. Using
the stability properties of these oscillations, bifurcation points are found at which new types of families of 3D periodic
orbits branch out of the Z-axis consisting of orbits located entirely above or below the orbital plane of the primaries. Several of the bifurcating
families are continued numerically and typical member orbits are illustrated. 相似文献
11.
We consider one-soliton perturbations of a flat Friedmann-Robertson-Walker (FRW) cosmological model, with an ideal fluid with pressure equal to the energy density (stiff fluid), in the case where the “pole trajectory” parameter is negative, introducing thereby singularities along certain null hypersurfaces. Starting with a metric that approaches asymptotically the FR W background, we show that it is possible to construct an extension through these hypersurfaces such that the energy momentum tensor Tab is finite and satisfies the energy conditions. The extension is only C1, providing a sort of “shock front” with continuity in Tab, that has an associated phase transition from null dust to stiff fluid, the transition being of the form described by CHANDRASEKHAR and XANTHOPOULOS. 相似文献
12.
I. K. Csada 《Solar physics》1981,74(1):103-105
The external field of the solar magnetohydrodynamic dynamo is expressed in terms of spherical harmonics and in powers of 1/r. The non-symmetric dynamo is stabilized by a -dependent rotational oscillation which interacts with the magnetic field, thus compensating for Ohmic loss. As a consequence, the axis of a dipole wave is found to move on a great circle, with revolution time equal to the magnetic cycle.Proceedings of the 14th ESLAB Symposium on Physics of Solar Variations, 16–19 September 1980, Scheveningen, The Netherlands. 相似文献
13.
A. Dinculescu 《Astrophysics and Space Science》2007,310(3-4):237-239
Starting from the assumption that the radiation source at the origin of the cosmic microwave background (CMB) could not have a luminosity larger than the maximum energy in ordinary matter divided by the minimum time allowed by causality,
one arrives at an expression that gives the energy density of CMB as a function of the main cosmological parameters. Also, by defining a radiation charge as the hypothetical charge that opposes
the congregation of a cloud of particles around a source of electromagnetic radiation, on arrives at another expression for
the energy density of CMB that agrees exactly with the measured value for a value of the Hubble constant equal to 72.09 km s−1 Mpc−1. Both expressions are independent of the redshift. 相似文献
14.
Josep M. Cors Jaume Llibre Merce Ollé 《Celestial Mechanics and Dynamical Astronomy》2004,89(4):319-342
We study the planar central configurations of the 1 +n body problem where one mass is large and the other n masses are infinitesimal and equal. We find analytically all these central configurations when 2≤n≤4. Numerically, first we provide evidence that when n9 the only central configuration is the regular n-gon with the large mass in its barycenter, and second we provide also evidence of the existence of an axis of symmetry for
every central configuration.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
A. Zalucha A. Fitzsimmons J.L. Elliot J. Thomas-Osip H.B. Hammel V.S. Dhillon T.R. Marsh F.W. Taylor P.G.J. Irwin 《Icarus》2007,192(2):503-518
We observed a stellar occultation by Titan on 2003 November 14 from La Palma Observatory using ULTRACAM with three Sloan filters: u′, g′, and i′ (358, 487, and 758 nm, respectively). The occultation probed latitudes 2° S and 1° N during immersion and emersion, respectively. A prominent central flash was present in only the i′ filter, indicating wavelength-dependent atmospheric extinction. We inverted the light curves to obtain six lower-limit temperature profiles between 335 and 485 km (0.04 and 0.003 mb) altitude. The i′ profiles agreed with the temperature measured by the Huygens Atmospheric Structure Instrument [Fulchignoni, M., and 43 colleagues, 2005. Nature 438, 785–791] above 415 km (0.01 mb). The profiles obtained from different wavelength filters systematically diverge as altitude decreases, which implies significant extinction in the light curves. Applying an extinction model [Elliot, J.L., Young, L.A., 1992. Astron. J. 103, 991–1015] gave the altitudes of line of sight optical depth equal to unity: 396±7 and 401±20 km (u′ immersion and emersion); 354±7 and 387±7 km (g′ immersion and emersion); and 336±5 and 318±4 km (i′ immersion and emersion). Further analysis showed that the optical depth follows a power law in wavelength with index 1.3±0.2. We present a new method for determining temperature from scintillation spikes in the occulting body's atmosphere. Temperatures derived with this method are equal to or warmer than those measured by the Huygens Atmospheric Structure Instrument. Using the highly structured, three-peaked central flash, we confirmed the shape of Titan's middle atmosphere using a model originally derived for a previous Titan occultation [Hubbard, W.B., and 45 colleagues, 1993. Astron. Astrophys. 269, 541–563]. 相似文献
16.
In this paper, families of simple symmetric and non-symmetric periodic orbits in the restricted four-body problem are presented.
Three bodies of masses m
1, m
2 and m
3 (primaries) lie always at the apices of an equilateral triangle, while each moves in circle about the center of mass of the
system fixed at the origin of the coordinate system. A massless fourth body is moving under the Newtonian gravitational attraction
of the primaries. The fourth body does not affect the motion of the three bodies. We investigate the evolution of these families
and we study their linear stability in three cases, i.e. when the three primary bodies are equal, when two primaries are equal
and finally when we have three unequal masses. Series, with respect to the mass m
3, of critical periodic orbits as well as horizontal and vertical-critical periodic orbits of each family and in any case of
the mass parameters are also calculated. 相似文献
17.
The concept of central configuration is important in the study of total collisions or the relative equilibrium state of a rotating system in the N-body problem. However, relatively few such configurations are known. Aided by a new global optimizer, we have been able to construct new families of coplanar central configurations having particles of equal mass, and extend these constructions to some configurations with differing masses and the non-coplanar case. Meyer and Schmidt had shown that a theorem of Palmore concerning coplanar central configurations was incorrect for N equal masses where 6 N 20 but presented a simple analytic argument only for N = 6. Using straightforward analytic arguments and inequalities we also disprove this theorem for 2N equal masses with N 3. 相似文献
18.
Tapan K. Chatterjee 《Astrophysics and Space Science》1987,139(2):243-256
The determination of the potential and force due to a thin exponential model disk galaxy and a polytropicn=4 model spherical galaxy are conducted in the light of the study of collision dynamics.Results indicate that the potential due to the sphere and the disk along its plane are equal at a distance of about 1/3R, whereR is the radius of either configuration. Interior to this distance, the potential due to the sphere is greater than that due to the disk and beyond this distancevice versa.These results are expected to lead to the construction of simple models for galaxies, useful in the study of collision dynamics. 相似文献
19.
We present results of an investigation of clustering evolution of field galaxies between a redshift of z ∼ 1 and the present epoch. The current analysis relies on a sample of ∼ 14000 galaxies in two fields of the COMBO 17 survey.
The redshift distribution extends to z ∼ 1. The amplitude of the three-dimensional correlation function can be estimated by means of the projected correlation function
w(r
p
). The validity of the deprojection was tested on the Las Campanas Redshift Survey (LCRS). In a flat cosmology with non-zero
cosmological constant for bright galaxies (M
B ≤-18) the clustering growth is proportional to (1+z)
-2. However, the measured clustering evolution clearly depends on Hubble type. While locally the clustering strength of early
type galaxies is equal to that of the bright galaxies, at high redshifts they are much stronger clustered, and thus the clustering
has to evolve much more slowly.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
J2 Invariant Relative Orbits for Spacecraft Formations 总被引：1，自引：0，他引：1
An analytic method is presented to establish J
2 invariant relative orbits. Working with mean orbit elements, the secular drift of the longitude of the ascending node and the sum of the argument of perigee and mean anomaly are set equal between two neighboring orbits. By having both orbits drift at equal angular rates on the average, they will not separate over time due to the J2 influence. Two first order conditions are established between the differences in momenta elements (semi-major axis, eccentricity and inclination angle) that guarantee that the drift rates of two neighboring orbits are equal on the average. Differences in the longitude of the ascending node, argument of perigee and initial mean anomaly can be set at will, as long as they are setup in mean element space. For near polar orbits, enforcing both momenta element constraints may result in impractically large relative orbits. It this case it is shown that dropping the equal ascending node rate requirement still avoids considerable relative orbit drift and provides substantial fuel savings.This revised version was published online in October 2005 with corrections to the Cover Date. 相似文献