Chinese Astronomy最新文献

In this paper we discuss the numerical stability of Cowell's method when applied to the Keplerian circular motion. The critical stepsize h_m is given for the PE, PECE and CE algorithms of various orders. A comparison of our results with others' shows our method to be more precise.

This is the first of two papers reporting the spectra of the Comet Arend-Roland (1956h) observed with the 82″ telescope at the McDonald Observatory, Texas, USA. In this paper we report the results of the analysis of two spectra, one in the range$\text{λλ3700}\text{A}\text{̊}\text{− 4800}\text{A}\text{̊}$. Having a dispersion of 36Å/mm and the other, $\text{λλ5100}\text{A}\text{̊}\text{−6800}\text{A}\text{̊}$ having a dispersion of 72Å/mm. (The second paper deals with the polarization of emission lines of the comet). The spectra show a very strong solar continuum shifted to the red because of the Doppler effect, indicating that the comet is very dusty. From the lengths perpendicular to the dispersion of the continuum on the spectrogram, we estimated the linear dimension of the coma of the comet as 4.3 × 10³km.

Using the data obtained at 4 observatories at Tianjin, Beijing, Shanghai and Wuhan, we have calculated the annual Z-term in the variation of latitude. We have investigated the stability of the calculated values over a period of some 15 years and used them to derive corrections to the various nutation terms.

In this paper, the inclination function is expressed in terms of the hypergeometric function and this has resulted in some simple recurrence relations involving no more than three neighbouring functions.

Initial temperature distribution of the nebulous disk around the sun led to the bordering region between the asteriods and Jupiter becoming a transition region, in which the “icy” matter changed from uncondensed to condensed state. This continuity in chemical constitution makes the projected surface density of solid condensate in the inner portion of the Jupiter region greater than the mean value in the asteriod region, and the time taken for dust particles to precipitate to become comparable to that in the asteriod region. Owing to gravitational instability, the dust layer then broke up into clusters of particles, each cluster transforming into a planetesimal. The mass of such a planetesimal and the rate of its growth in the Jupiter region are greater than those in the asteriod region. Perturbations and mutual encounters between the larger planetesimals in the inner portion of the Jupiter region changed their orbits and produced rather large relative velocities. Some of these entered the asteriod region, drew out most of the matter there, and increased the random velocity of the asteriods that remained, so that they could not combine to form a planet. We prove the above view by a quantitative analysis in this paper.

Nova Vulpeculae was observed from November 11 to December 16, 1976, at the Beijing Observatory with the grating spectrograph attached to the Cassegrain focus of the 60/90 Schmidt telescope.

This paper gives the idectification of the spectral features, the expansion velocities, the photoionization temperatures, the colour temperatures and the Balmer decrement. In wavelength range λλ 3400 – 6700 the principal lines are of HI, FeII, NaI, NII, CaII, TiII, [OI], [NII] atoms or ions. The majority of lines are of P Cyg type. The expansion velocities as derived from measurements of the absorption spectra amount to about 500 – 2200 km/s. Photoionisation temperatures are higher than the corresponding colour temperatures. They increased as the nova became fainter.

Based on the similarity in the variation of sunspot number in the ascending branch between Cycle 21 and Cycles 3, 8, 18, we predict that the solar activity in Cycle 21 will probably be high, with a maximum smoothed monthly mean relative number of 149.4 and the maximum epoch will be 1979.7.

A first-order asymptotic solution (rapid phase variation) of the Poisson's equation for the three-dimensional potential in a special model is applied to a stationary, polytropic gas disk. After considering the vertical motion and the three-dimensional distributions of the physical parameters, a dispersion relation is derived. Numerical examples are calculated for the Schmidt model galaxy and for a thick galaxy to illustrate the variation of the wave number with height which may possibly account for certain observed facts about spiral arms.

The result that there is a time-lag between Type-I radio bursts and associated flares given in a previous paper [1] is confirmed by new statistical material.