海尔—波普彗星的一个可能的巨大等离子体喷流

１９９６年９月１１日，使用上海天台１．５６ｍ望远镜和Ｓｅｒｉｓ２００ＣＣＤ照相机，在Ｂ波段发现海尔－波普彗星有一个巨大的喷流，初步认定为等离子喷流。     

海尔—波普彗星喷流的一次成功检测

上海天文台余山观测站1．56m望远镜于1996年9月23日北京时间19点40分拍摄了海尔-波普彗星的CCD图象。使用的滤光片是R，露光时间为45s。经过偏流（bias）、暗流（dark）以及平场（flat）改正的图象上可以看出彗核附近有5条喷流，但是并不十分清楚（见图1）。这主要是由于喷流叠     

1997年3月4日海尔-波普彗星的小规模分裂

１　引言彗核分裂是彗星的最重要特征之一．至１９８２年止文献记录共观测到２２个彗核分裂,３３个次核［１］．１９８６年哈雷彗星回归时观测到彗核的分裂［２］．１９９６年紫金山天文台２００ｍｍ赤道望远镜和青岛观象台同时观测到百武彗星的分裂［３］．海尔波普彗星从１９９５年８月到１０月曾爆发５次［４］．１９９６年３月至１２月不断有喷流射出,彗核活动日趋剧烈［５］．１９９７年３月４日我们观测到彗核的小规模分裂及喷流特征,３月３日我们观测到海尔波普彗星近核照片上有喷流,这可能是３月４日彗核小块分裂的前奏．３…     

Hale-Bopp 彗星喷流结构的周期变化

通过对上海天文台佘山观测基地１９９７年３月至５月初期间所得到的Ｈａｌｅ－Ｂｏｐｐ彗 星喷流观测资料的处理和分析,发现该彗星的喷流结构有周期性变化,其周期为８—９ 天,这种周期变化可能与彗星的自转轴在空间的进动周期有关．     

海尔—波普彗星近核区图像增强方法及比较

用Ｓｅｋａｎｉｎａ 等的方法和小波处理方法分别对１９９７ 年３ 月３ 日至５ 日在紫金山天文台行星室观测得到的海尔－ 波普彗星的近核现象ＣＣＤ 图像加以增强处理和分析比较,明显地从ＣＣＤ 图像还原出壳层（ｓｈｅｌｌ） 和喷流（ｊｅｔ） 结构,结果表明小波处理方法比Ｓｅｋａｎｉｎａ 等的方法在小视场图像处理中效果更佳     

Hale—Bopp彗星喷流结构的周期变化

通过对上海天台佘山观测基地１９９７年３月３至５月 初期间所得到的Ｈale－Ｂｏｐ ｐ彗星喷流观测流观测资料的处理和分析,发现该彗星的喷流结构有周期性变化,其周期为８－９天,这种周期变化可能与彗星的自转轴在空间的进动周期有关。     

3C390．3的弱秒差距尺度喷流及其变化

通过对射电星系３Ｃ３９０．３在历元１９８９．２９及６ｃｍ波长的ＶＬＢＩ观测数据的多软件包成象，辨认出其弱秒差距尺度喷流中几个分离的节，将它们和以前发表及未发表的同一波长的成象结果比较，显示了该源弱秒差距尺度喷流的弯曲和反喷流，并重新证认了喷流中节的视超光速运动。     

3C390.3的弱秒差距尺度喷流及其变化

通过对射电星系３Ｃ３９０．３在历元１９８９．２９及６ｃｍ波长的ＶＬＢＩ观测数据的多软件包成象，辨认出其弱秒差距尺度喷流中几个分离的节，将它们和以前发表及未发表的同一波长的成象结果比较，显示了该源弱秒差距尺度喷流的弯曲和反喷流，并重新证认了喷流中节的视超光速运动。     

SL9彗星撞击木星时S碎片的CCD观测

用上海天台１．５６ｍ望远镜和ＣＣＤ照相机，观测Ｓ＝５碎片时，发现了类似彗尾的奇异现象。     

SL9彗星撞击木星时S碎片的CCD观测

用上海天文台１．５６ｍ望远镜和ＣＣＤ照相机，观测ｓ＝５碎片时，发现了类似彗尾的奇异现象。     

Closed solution of the Hill differential equation for short arcs and a local mass anomaly in the central body

The Hill differential equation describes the relative motion of a satellite w.r.t. a circular reference orbit. The deviations in the orbit are caused by a residual acceleration, which is small compared to the effect of the central gravitational field. In this paper, the acceleration of a local mass anomaly in the central body is considered, which rotates w.r.t. the inertial frame with a constant angular velocity. The mass anomaly is modeled by a superposition of radial base functions. The potential and the gradient of each base function are represented in the orbit by the Keplerian elements, the rotation rate of the central body and the parameters of the base function, i.e. the position of its center, the shape and a scaling factor. The inhomogeneous solution of the Hill differential equation for short arcs is found by means of the Laplace transform. A few lower orders of the solution require an additional Laplace transform, to consider the so-called resonance cases. The final deviations are described in a closed and differentiable formula of the Keplerian elements and the parameters of the base function.     

Substorm related changes in the geomagnetic tail: the growth phase

Changes in the configuration of the geomagnetic tail are known to play a fundamental role in magnetospheric substorms. Observations with the UCLA magnetometer on the eccentric orbiter OGO-5 indicate that the most pronounced changes in the midnight meridian occur in the cusp between 8 and 11 R_e. In order to organize the observations it is necessary to separate effects on the tail due to the solar wind magnetic field and effects due to substorms. Provided there are no changes in the solar wind there are two distinct phases of a substorm in the near tail: a growth phase and an expansion phase. During each phase the observations depend on the location of the satellite relative to the plasma sheet boundaries. Far behind the Earth is the pure tail region which consists of the lobe and the plasma sheet. In the lobe the field magnitude is characteristically enhanced relative to the dipole. Closer to the Earth is a region of transition. The field magnitude is close to that of the dipole but its orientation is distorted forming a cusp-like field line. Near the Earth is a region of depressed field. Here the field magnitude is much less than that of the dipole, but its orientation is similar. The growth phase of a substorm appears to be the direct consequence of the onset of a southward solar wind magnetic field. In the pure tail region the lobe field begins to increase in magnitude and the plasma sheet thins. The transition region moves earthward and the field lines become more tail-like as the field magnitude increases. In the inner region of depressed field, the field magnitude decreases rapidly. The onset of the expansion phase appears to be a process internal to the magnetosphere and independent of the solar wind. In the depressed field region there is a rapid, turbulent increase in field magnitude. In the transition region there is a sudden decrease in the field magnitude and a return to dipolar orientation. In the tail region the plasma sheet expands rapidly with the field becoming quite dipolar, decreasing slowly in the lobe of the tail.     

The solution of Jacobi's virial equation for celestial bodies

A relationship between the potential energy and the moment of the inertia for celestial bodies is heuristically discovered. This relationship consists in the constancy of the product of formfactors for the potential energy and the moment of the inertia. The product is independent of the body mass and its radial mass distribution.We find the exact solution of Jacobi's virial equation for a gravitating spherical body based on the relationship obtained. This solution represents the unharmonic radial oscillations of the body. The solution is valid for a wide class of celestial bodies including variable stars and relativistic objects for which a relativistic analog of Jacob's equation is derived.The period of the radial oscillations of the planets is estimated with the help of the solution found. We note the coincidence of the experimental data and our theoretical calculations for the Sun.We show the important role of the Coulomb forces in the formation of the planets. It is demonstrated that the Coulomb forces result in the relation between the planet masses and their average molecular weight.     

The specific features of the evolution of the viscous protoplanetary circumsolar disk

The problem of angular-momentum and mass transport in the disk is discussed and the disk viscosity is estimated. The evolution of the gas-dust protoplanetary disk at the stage of its formation inside the protostellar (protosolar) accretion envelope is considered. The conditions for the radial growth of the disk are estimated. For the subsequent period, when the central star (young Sun) is in the T Tauri phase, the temporal variations of the radius, mass, and the surface density of the disk, as well as the total mass flux from the disk onto the star (Sun), i.e., the mass accretion rate, are evaluated. The constraints on the initial value of the angular momentum of the protoplanetary circumsolar disk (that is, on the angular momentum of the protosolar cloud) are discussed with due regard for cosmochemical data.Translated from Astronomicheskii Vestnik, Vol. 38, No. 6, 2004, pp. 559–576.Original Russian Text Copyright © 2004 by Makalkin.     

The origin of the atmospheres of the earth and the planets

From a systematic analysis of the whole history of the protoplanetary cloud and the observational facts of the Earth's atmosphere, we propose a new theory of the origin of the atmospheres of the Earth and the planets. For the Earth-like planets, there were extended primordial atmospheres originating from the protoplanetary cloud by the accretion of the planetary embryoes. These primordial atmospheres existed on a time scale of 10³–10⁷ years and were composed of chemically reducing gases. The presence of such a reducing atmosphere may be of great significance to the theories of cosmogony and the origin of life.The contents are 1. The escape of the nebula and the planetary atmospheres. 2. The thermal dissipation of the atmospheres and their blowing-off by the solar wind. 3. The accretion of gases by the planetary enbryoes. 4. The primordial atmospheres.     

A mechanism for the growth phase of magnetospheric substorms

A mechanism is presented whereby the rate of energy dissipation in the magnetosphere is controlled by the particle density in the plasma sheet in the near geomagnetic tail. The mechanism is based on a model in which the plasma sheet is sustained by injection of solar-wind particles into the dayside magnetosphere. The efficiency of the injection is controlled by solarwind parameters, in particular, the north-south component of the interplanetary magnetic field; the maximum injection rate occurs when the interplanetary field is northward. During geomagnetically quiet times, this source balances the loss of particles from the edges of the tail current sheet. If the dayside source rate is reduced (e.g. by a southward-turning interplanetary magnetic field), then the plasma sheet is depleted and the rate of magnetic merging is enhanced in the earthward portion of the tail current sheet. This period of steadily-enhanced merging is associated with the growth phase, i.e. the period of enhanced magnetospheric convection for about one hour preceding the breakup of a polar magnetic or auroral substorm. The breakup can be understood as the result of the collapse of a portion of the tail current sheet following the local depletion of the plasma sheet.     

Correlations Between Color Gradients and Structural Parameters of Disks in Late-type Spiral Galaxies

From the second group of the data released by the Sloan numerical patrol survey (SDSS DR2), 395 face-on late-type spiral galaxies brighter than 15-th magnitude in the waveband r are selected as the sample. The relations between the color gradients and structural parameters of disks are studied. The results indicate the following: (1) The color gradient is independent of the absolute magnitude (mass) of the disk. (2) The color gradient of disk is concerned with the size of disk. The larger the disk, the steeper the color gradient. (3) The color gradient of disk is concerned with the color of disk. The bluer the disk color, the steeper the gradient. (4) The color gradient of disk is related with the surface brightness of disk. The brighter the disk, the steeper the color gradient. Moreover, the historical constraint formed by the relations between the color gradients of disks and various structural parameters is briefly discussed.     

Precision of the ephemerides of outer planetary satellites

Ephemerides of planetary satellites are needed to address many problems. These ephemerides are used for subsequent observations. A comparison of the available ephemerides with new observations allows the accuracy of the former to be assessed. However, the precision of the ephemerides must be known a priori when solving the tasks. In this paper we formulate and solve the problem of estimating the precision of the ephemerides of outer planetary satellites derived from observations when applied up to the future moments.The methods of assessing the precision of ephemerides involve producing a set of samples of the same ephemeris inferred from observations with different samples of Monte Carlo generated random errors (RO) superimposed onto it. The statistical parameters of simulated observational errors are based on the results of the reduction of real satellite observations. We compute the deviations of the samples of the ephemeris from the standard ephemeris inferred from real observations and adopt the root-mean-square deviation of the apparent coordinates as the precision of the ephemeris. We also use alternative methods: one based on the matrix of covariances of parameter errors (RP), and another one based on bootstrap samples of observations (BS).We use three methods (RO, RP, and BS) to estimate the precision of the ephemerides of all the 107 outer planetary satellites over the 2010-2020 time interval. The precision of the ephemerides of different satellites varies from 0.05 to 4.0 arcsec. For a number of satellites new observations are of vital importance for maintaining the precision of the ephemerides at a level that would allow identification of satellites during the reduction of observations. For some satellites the precision of their ephemerides is of the order of the sizes of their orbits and such satellites can be considered to have been lost. We show that the method of bootstrap samples (BS) can give doubtful results in the cases where there are few observations, which covered a time interval that is shorter than the orbital period of the satellite.Our results suggest obtaining more precise ephemeris making new observations at the times of maximum estimated errors of the ephemeris.All the inferred estimates of the precision of ephemerides are available from the MULTI-SAT ephemeris server: www.imcce.fr/sat (IMCCE), www.sai.msu.ru/neb/nss/index.htm (SAI).     

The Oscillations of Coronal Loops Including the Shell

We investigate the MHD waves in a double magnetic flux tube embedded in a uniform external magnetic field. The tube consists of a dense hot cylindrical cord surrounded by a co-axial shell. The plasma and the magnetic field are taken to be uniform inside the cord and also inside the shell. Two slow and two fast magnetosonic modes can exist in the thin double tube. The first slow mode is trapped by the cord, the other is trapped by the shell. The oscillations of the second mode have opposite phases inside the cord and shell. The speeds of the slow modes propagating along the tube are close to the tube speeds inside the cord and the shell. The behavior of the fast modes depends on the magnitude of Alfvén speed inside the shell. If it is less than the Alfvén speed inside the cord and in the environment, then the fast mode is trapped by the shell and the other may be trapped under the certain conditions. In the opposite case when the Alfvén speed in the shell is greater than those inside the cord and in the environment, then the fast mode is radiated by the tube and the other may also be radiated under certain conditions. The oscillation of the cord and the shell with opposite phases is the distinctive feature of the process. The proposed model allows to explain the basic phenomena connected to the coronal oscillations: i) the damping of oscillations stipulated in the double tube model by the radiative loss, ii) the presence of two different modes of perturbations propagating along the loop with close speeds, iii) the opposite phases of oscillations of modulated radio emission, coming from the near coronal sources having sharply different densities.     

A relaxation method for the computation of model stellar atmospheres

A general Monte Carlo relaxation method has been formulated for the computation of physically self-consistent model stellar atmospheres. The local physical state is obtained by solving simultaneously the equations of statistical equilibrium for the atomic and ionic level populations, the kinetic energy balance equation for the electron gas to obtain the electron temperature, and the equation of radiative transfer. Anisotropic Thomson scattering is included in the equation of transfer and radiation pressure effects are included in the hydrostatic equation. The constraints of hydrostatic and radiative equilibrium are enforced. Local thermodynamic equilibrium (L.T.E.) is assumed as a boundary condition deep in the atmosphere. Elsewhere in the atmosphere L.T.E. is not assumed.The statistical equilibrium equations are solved with no assumptions made concerning detailed balance for the bound-bound radiative processes. The source function is formulated in microscopic detail. All atomic processes contributing to the absorption and emission of radiation are included. The kinetic energy balance equation for the electron gas is formulated in detail. All atomic processes by which kinetic energy is gained and lost by the electron gas are included.The method has been applied to the computation of a model atmosphere for a pure hydrogen early-type star. An idealized model of the hydrogen atom with five bound levels and the continuum was adopted. The results of the trial calculation are discussed with reference to stability, accuracy, and convergence of the solution.Contribution No. 385 from the Kitt Peak National Observatory.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.