共查询到20条相似文献，搜索用时 593 毫秒
1.
An effect of the solar wind on the motion of interplanetary dust particles is investigated. An equation of motion is derived. It is pointed out that the Pseudo-Poynting-Robertson effect (and its special case — a corpuscular drag) and the corpuscular sputtering represent in reality one and the same effect within the framework of special relativity. In this context perturbation equations of celestial mechanics are also discussed. 相似文献
2.
Computations of polarization and intensity of radiation from a unit stellar surface area are presented, as well as a study of the numerical characteristics of atmospheres — single-scattering albedo and the initial source function(), which define the polarization behaviour of atmospheres. The radiatively stable models of stellar atmospheres presented by Kuruczet al. (1974) and Kurucz (1979) have been used for calculations. Since the versus optical depth dependence is rather weak, it has been assumed that (=cost. With a fixed effective temperatureT
eff maximum values of are characteristic of stars featuring the lowest surface gravity accelerationg. Among stars with radiatively stable atmospheres, maximum values of (=5000 Å) 0.4–0.6 are exhibited by supergiants withT
eff=8000–20 000 K. The plot of () is characterized by discontinuities at the boundaries of spectral series for hydrogen and, sometimes, for helium. Maximum are attained in the Lyman region of =912–1200 Å, where can reach the value 0.7–0.9 for supergiants, this value being 0.3 for Main-Sequence stars. For stars withT
eff 35 000 K, high values of also are attained for <912 Å. Within the infrared region, is always small because of bremsstrahlung absorption.A rapid growth of the source functionB
with < typical for ultraviolet range (within the Wien part of spectrum), together with high values of results in the strong polarization of emission from a unit stellar surface element, sometimes exceeding the values for the case of a pure electron scattering. For longer wavelengths, where the limb-darkening coefficient is smaller, the plane of polarization abruptly turns 90° in the central parts of the visible stellar disk. 相似文献
3.
A. V. Krivov L. L. Sokolov V. V. Dikarev 《Celestial Mechanics and Dynamical Astronomy》1995,63(3-4):313-339
This paper deals with dynamics of impact ejecta from Phobos and Deimos initially on near-circular equatorial orbits around Mars. For particles emitted in a wide size regime of 1 micron and greater, and taking into account the typical particle lifetimes to be less than 100 years, the motion is governed by two perturbing forces: solar radiation pressure and influence of Mars' oblateness. The equations of motion of particles in Lagrangian non-singular elements are deduced and solved, both analytically and numerically, for different-sized ejecta. We state that the coupled effect of both forces above is essential so that on no account can the oblateness of Mars are be neglected. The dynamics of grains prove to be quite different for the ejecta of Phobos and Deimos. For Deimos, the qualitative results are relatively simple and imply oscillations of eccentricity and long-term variations of orbital inclination, with amplitudes and periods both depending on grain size. For Phobos, the dynamics are shown to be much more complicated, and we discuss it in detail. We have found an intriguous peculiar behavior of debris near 300 µm in size. Another finding is that almost all the Phobos ejecta with radii less than 30 µm (against the values of 5 to 20 µm adopted earlier by many authors) should be rapidly lost by collisions with martian surface. The results of the paper may be the base for constructing an improved model of dust belts that presumably exist around Mars. 相似文献
4.
P. Brosche 《Astrophysics and Space Science》1978,57(2):463-467
The empirical evidence for a connection between type and relative angular momentum of galaxies is reviewed and some constraints for the theoretical explanation are discussed.
.相似文献
5.
Max K. Wallis 《Astrophysics and Space Science》1973,20(1):3-18
The interaction processes governing the penetration of the interstellar gas into the solar neighbourhood are re-examined — as well as photo-ionization and charge-exchange processes, proton elastic collisions and electron ionizations help reduce the nearby gas densities. The total destruction rate varies little during the solar cycle, by perhaps 10%. Particle heating, particularly via the elastic collisions, determines the gas characteristics in the gravitationally focussed tail—enhanced H-density is prevented, while the He-tail is effectively hotter than 103 K.Termination of the solar wind is rediscussed in the light of both electron heating and the stronger gas/plasma interaction. The spiral interplanetary field is taken to break up and the subsonic plasma flow to be controlled by the pressure of slowly cooling electrons. The terminating collisionless shock is then, if it exists at all, very weak (M
1<1.4), subcritical, and energetically unimportant. Cosmic rays are little affected by this sonic transition, but at least the electron component should be modulated by plasma turbulence throughout the ionizing flow.
. , . , . . .相似文献
6.
Г. А. Гурзадян 《Astrophysics and Space Science》1977,46(2):471-484
, , , , ,S
, , , S
Mg. , . , . , ( , ..). B5 B0; (<1%). 相似文献
7.
, , , , . , . , () (), , , . — . 相似文献
8.
H. Zimmermann 《Astrophysics and Space Science》1986,128(1):33-42
It is shown that on theoretical grounds the relative abundances of the elements in the interstellar gas phase should be correlated with the wavelength of maximum interstellar polarization max. If these correlations can be determined by observations, then there is the possibility to determine the relative abundances of the heavier elements within the mantles as well as within the cores of interstellar dust grains, at least in principle.The observational data available up to now confirm the existence of such correlations between max and the interstellar gas phase abundances of titanium, iron, magnesium, and carbon. Statements about the chemical composition of the dust particles are not yet possible. For this there are observations of the interstellar gas depletion needed, especially in such lines of sight where max has extreme values.Paper presented at a Workshop on The Role of Dust in Dense Regions of Interstellar Matter, held at Georgenthal, G.D.R., in March 1986. 相似文献
9.
G. A. Krasinsky 《Celestial Mechanics and Dynamical Astronomy》1972,6(1):60-83
The general conception of the critical inclinations and eccentricities for theN-planet problem is introduced. The connection of this conception with the existence and stability of particular solutions is established. In the restricted circular problem of three bodies the existence of the critical inclinations is proved for any values of the ratio of semiaxes . The asymptotic behaviour of the critical inclinations as 1 is investigated.
. . . 1.相似文献
10.
The observed variation of reddening as function of the heliocentric distance and the spatial variation of reddening within the coma of Comet West in the visual wavelength range have been considered to infer the properties of the cometary dust grains. The relevant model incorporates the variation in the size distribution function as well as the composition of the spherical grains. The real part of the complex index of refraction (m = m – im) is chosen such thatm = 1.6. The imaginary part is required to vary from m = 0.2 to 0.05 over the wavelength range 0.4 to 0.7 m. This choice of refractive index corresponds to dirty silicate grains. As a by-product, the model also satisfies the observed polarization and albedo for the Comet West. 相似文献
11.
12.
Г. А. Гурзадян 《Astrophysics and Space Science》1979,64(1):3-23
2800 Mgii (. 1). (N
+/N
11000) , , (N
+/N
110). , . —, , . — . : ; 0.002 1 , 0.1 ; () 100 –3; ; ; , 10
; 10–4
1
. 2800 Mgii . 相似文献
13.
Р. М. Мурадян 《Astrophysics and Space Science》1980,69(2):325-337
, J=(m/m
p)1+1/n
, n=2 , n=3 , . , . , , . - wc m
P, G c . -. 相似文献
14.
F. W. Stecker 《Astrophysics and Space Science》1970,6(3):377-389
The cosmic -ray spectrum below 1 GeV arising from cosmic ray p-p interactions is calculated. Its characteristics are determined by the properties of secondary neutral pion production occurring at accelerator energies. A model is chosen for numerical calculations in which the two dominant modes of neutral pion production at accelerator energies are the production of the (1.238) isobar and one fireball. The effect of -p and p- interactions on the cosmic -ray spectrum is also calculated. The final results are given in terms of both differential and integral -ray energy spectra. 相似文献
15.
К. А. Пирагас В. И. Жданов А. Н. Александров И Л. Е. Пирагас 《Astrophysics and Space Science》1978,57(2):283-302
- , . . , . - . 相似文献
16.
In this paper we investigate the properties of dust in circumstellar shells around very young massive compact IR sources (Becklin-Neugebauer objects).We found no correlation between the optical depth in the centre of the 10-m band and the 3.1-m ice band. An inverse correlation between the strength of the silicate feature and the colour temperature for the 8–13 m interval was detected. Our sample of BN objects extends this kind of relation already known for Mira stars and OH/IR stars to higher optical depths.We present a radiative transfer model for BN objects and discuss its main properties. Using this model, the interpretation of the observations led to the conclusion that the type of silicates present in the dust shells of very young stellar objects is different from that type around oxygen-rich giants and supergiants. These different silicates may be tentatively identified with pyroxenes and olivines, respectively.We studied the influence of the adopted dust model in deriving source parameters of BN objects. The object W3-IRS5 was discussed in some detail.Paper presented at a Workshop on The Role of Dust in Dense Regions of Interstellar Matter, held at Georgenthal, G.D.R., in March 1986. 相似文献
17.
. , , . , t>1010 ( z<105) .
In this paper we continue the work of Weymann, investigating the causes of distortion of the spectrum of the residual radiation from the Planck curve. We discuss the distortion to the spectrum, resulting from recombination of primeval plasma.We then derive an analytic expression for the distortion to the equilibrium spectrum due to Compton scattering by hot electrons. On the basis of the observational data we conclude that a period of the existence of neutral hydrogen is inescapable in the hot model of the universe. It is concluded that any injection of energy att>1010 sec (red shiftz<105) give the distortions of the equilibrium spectrum.相似文献
18.
A quantum mechanical treatment of an electron plasma in a constant and homogeneous magnetic field is considered, with the aim of (a) defining the range of validity of the magnetoionic theory (b) studying the deviations from this theory, in applications involving high densities, and intense magnetic field. While treating the magnetic field exactly, a perturbation approach in the photon field is used to derive general expressions for the dielectric tensor . The properties of are explored in the various limits. Numerical estimates on the range of applicability of the magnetoionic theory are given for the case of the one-dimensional electron gas, where only the lowest Landau level is occupied. 相似文献
19.
Constantin Kholchevnikov 《Celestial Mechanics and Dynamical Astronomy》1971,3(2):232-240
The potential of a body of revolution is expanded in a series of spherical functions. It is proved that, for a body with analytical density limited by an analytical surface the coefficients of expansion decrease in geometrical progression.
. , , , .相似文献
20.
, . . . (10R
) ( 10 000R
). NGC 5457, NGC 6946 NGC 5236. , , II I . . . , . . 1050÷1052 , . 相似文献