Chinese Astronomy最新文献

The effects of Oppolzer terms on the determination of latitude variation, polar motion and declination are discussed. We suggest that the celestial pole may be defined as the intersection of the rotation axis, corrected for the lunisolar polar motion with the celestial sphere. Or approximately, it may be defined as the intersection of the diurnal mean direction of rotation axis with the celestial sphere.

The hexagram “Feng” of the “Book of Changes” (completed before 800 B.C.) contains the statements “a dou is seen in the Sun” and “a mei is seen in the Sun”. The character dou (bushel) is generally understood to refer to an obscured region in this context. As to the character mei, a passage in the “Biography of Wang Mang” in “The History of the Later Han Dynasty“ written in 450 A.D. shoes that it is synonymous with the character xing (star), and according to “Kaiyuan Treatise on Prognostication” written in 729 A.D., both dou and xing in this context refer to an obscuration. Lastly, in the years 1626, 1643 and 1684, years of relatively high solar activities over the period 1610–1700 (Eddy, Science$\text{192}$ (1976) 1189), when sunspots were seen in telescopes in Europe (cf. Bray and Loughhead, “Sunspots” 1964, Plate 1.1), these two very same statements are found in some Local Gazettes of China (Xu Zhen-tao and Jiang Yao-tiao, Annals of Nanjing University, (Natural Sciences Series), No. 2, 1979). Thus, the earliest written record of a sunspot is found in China, in this book which was completed before 800 B.C.

By analysing the differences between simultaeous latitude measurements by different instruments at one and the same station, we demonstrate that the actual accuracy of latitude observations is much less than the internal accuracy of one instrument and we conclude that the local (non-polar) term is mainly due to various errors such as the irregular refraction in the observing room, and not due to geophysical factors such as tectonic movement and a change of plumb line.

We discuss the dispersion relation of local linear waves in a compressible and perfectly conducting gas possessing magnetic and gravitational fields in a slowly rotating frame of reference. Instead of the full energy equation and a gas law, a not necessarily adiabatic equation of state p=p(ϱ) is used to close the system of equations, — an arguably flexible way of treatment when we are not clear about the contributions by radiation and conductivity to the energy transport.

We give a general dimensionless dispersion relation, (8). This reduces to (9) if the magnetic field B is zero; to (10) if, further, rotation φ is zero; to the relation for accoustic waves (11), if further the gravitational field G is zero. When B is not zero, we consider various cases with the propagation vector K always perpendicular to B: the relation now reduces to (13) if K is not perpendicular to φ; to (14) if, further, K is parallel to G; to (15) if φ=0; to the relation for last magneto-accoustic waves (16) if G=0. It reduces to (17) if K is perpendicular to G; to the fast magneto-accoustic waves (18), if, further, φ=0. It reduces to (19) if K is perpendicular to φ and to (20), if, further, K is parallel to G.

Our study shows that, in general, there are no pure modes, only hybrids. In particular, a rotation gives rise to modes that are dependent on the latitude, which we call “physico-geometrical” waves.

The present study is preliminary, and we may expect even more interesting results when we take into consideration the energy equation and the effects of radiation.

On the basis of our numerical solution of the equations of transfer of Stokes parameters, we have established in this paper a method for the determination of the magnetic field strength H and the angle between the field line and the line of sight γ, using observed profile of parameter Q.

In 1977, we continued our cooperative observations in the Sco-Oph region with the Schmidt telescope of the Beijing Observatory and the twin-tube refractors of the Purple Mountain Observatory and the Beijing Observatory. After blinking and measuring, two flare stars and 15 variable stars were found. The results are given in TABLE 1. The identification charts and photographic reproduction of the two flare stars during their outbursts are presented in Fig. 1. The identification charts of the variable stars, with the exception of two variable stars in M4, are shown in Fig. 2. The light curves of most of the variable stars are presented in Fig. 3

The fact that the peculiar velocities of stars follow an ellipsoidal distribution implies that the perturbations on a pattern of density waves are unstable. The instabilities give rise to an amplification of the waves, which can compensate completely Toomre's dissipation and maintain the waves for a long time.

We have analysed spectroscopic data of 461 white dwarfs and obtained preliminary results as follows: (1) At present, the observed luminosity function agrees about equally well with the crystallization theory as with the non-crystallization theory. (2) White dwarfs appear to form an unbroken sequence on the H-R diagram. (3) The different locations on the diagram are mainly due to differences in temperature and in the degree of internal mixing. Evolution from early to late spectral types may exist.

When X-ray observations and the age of a SNR are known, basic physical parameters can be found either for an adiabatic phase model or an early phase (free expansion) model. The results obtained for the 3 objects SN185, SN1006 and SN1054 show that, in each case, the early phase models agree with ancient observations. For SN185 and SN1006, the early phase model gives a low medium density and much smaller distance than previously, suggesting a much lower radio luminosity-the correlated presence of these two features is favourable to the view that radio emission arises from the interaction between shock waves and the interstellar medium.

A twin tube chromospheric-photospheric telescope patrols and observes the solar chromosphere in H_α and the photosphere photographically and visually at the same time. Both objectives have apertures of 180 mm, and the polarizing interference filter in the main optical path of the chromospheric part has a working wavelength of 6562.78 a (H_α), a transmission half-width of 0.5 A, and is composed of 10 birefringent crystal elements, of which the last 4 are wide-field elements. Interference filters to cut down light are used in both the chromospheric and the photospherice paths and the solar image is, respectively, 25 and 71 mm in size. Test photographs show a quality that is better than any attained so far in China.