地球自转长期变化的最新结果

地球自转长期变化的研究依赖于古代天象记录.近年来这方面研究取得明显进展.本文着重介绍作者由中国古代公元十世纪以前732个月掩犯记录得到的最新结果,并与其他结果进行了对比和综合分析,中国月掩犯记录填补了公元三至八世纪的资料缺环,并证实了公元五世纪前后地球自转非潮项的明显变化.     

中国古代月与行星掩犯恒星记录及其用于传统星名考证

月与行星掩犯恒星的记录是中国古代天象记录中数量最多的门类,此类记录的可靠性比较高,自北宋开始,月与五星掩犯恒星的错误率平均为10%,而之前的平均错误率也仅有20%。统计分析了这些记录在历代正史中的分布。在用现代天文学计算方法检验的基础上,考证了中西黄道区星名的对应关系。     

掩星情报站

这个月只有两次适合观测的月掩星,分别是发生在11日晚的月掩人马座56号星,28日凌晨的月掩狮子座6号星。小行星掩星有六次掩星时间超过3秒钟的,其中掩食时间最长的可达8.9秒,一个月之内相继有六次掩食时间超过3秒的掩星事件是非常少见的,是一次非常难得的观测良机。     

掩星情报站

这次月掩星有个特点,就是两次月掩星的被掩星都是4．3等,而且月初的月掩摩羯座8星只有南方地区可见,中旬的月掩星只有北方地区可见。小行星掩星依然有四次,这四次小行星掩星中,最亮的被掩星是4．8等星。因为小行星掩亮星的机会非常少见,所以这次掩星对爱好者来说无疑是一次难得的观测良机。     

掩星驿站

金秋十月是个收获的季节,对掩星爱好者来说,同样是个观测掩星的良好时机,因为本月适合观测的掩星事件有十次之多,其中月掩星和小行星掩星事件分别各有五次,均适合爱好者进行观测。在五次月掩星事件中,有四次发生在凌晨,被掩星最亮的达2．3等。     

掩星情报站

2月份适合观测的月掩星和小行星掩星并不多,我们可以看到一次月掩星现象,六次小行星掩星现象。其中有四次小行星掩星适合多个地点进行联合观测,这四次小行星掩星中被掩星最亮的是8．2等,也是掩食时间最长的,可达16．7秒。     

《明实录》天象记录的统计分析

《明实录》是明朝历代官修的编年体史书,篇幅巨大,其中包含天象记录达6000余条,是二十四史以外中国古代天象记录的最大来源,其中包括日月食336条、月行星掩犯2622条、流陨2248条.明后期除日月食和彗星记录外,其他类型天象记录大幅减少.天象记录的密度,正德以前平均每年38条,嘉靖以后则只有每年7条.由可以回算验证的月行星掩犯记录得到错误率4.1%,属历代最佳.错误主要是资料编纂整理过程和书籍传抄过程造成的.月亮记录显示,凌晨的观测,通常记前一日日期;掩犯恒星记录显示,官内星名与传统略有差异.若干例证说明,原始记录采用日序式纪日.只是在编纂史书时,才改用干支纪日.     

掩星情报站

月掩星虽然经常发生,但受天气、月相、月球高度、被掩星亮度等因素影响,未必每一次都能观测成功,甚至一两个月观测不到一次也是可能的,这就使得月掩星的观测成为爱好者喜欢挑战的一个观测项目。本月就仅有一次适合观测的月掩星,而适合观测的小行星掩星也仅有四次。     

掩星情报站

六月份有四次月掩亮于五等星的现象,其中有两次在三等星左右,分别是4日凌晨月掩3.3等的人马ι星和7日凌晨月掩2.9等的摩羯δ星。月掩人马ι星我国除浙江到广东东南沿海地区、海南和黑龙江东部不可见之外均可观测到,而月掩摩羯δ星中国、蒙古和俄罗斯东部地区可见,但我国只有位于北纬32度以北的绝大多数地区的爱好者可以观测到,尤其值得注意的是,在大城市中合肥和南京市可见掠掩,也就是这两个城市的观测者     

掩星情报站

月掩天蝎座α星无疑将成为本月三次较适合观测的月掩星中最大的亮点,这次月掩天蝎座α星全国大多数地区可见,月掩双鱼座入星东北、华北和华东地区观测条件最好,月掩白羊座8星只有东北地区可见。     

Some results of investigations of aurorae and night airglow during the I.G.Y. and I.G.C.

A general review is given of the results of the airglow and auroral investigations during I.G.Y and I.G.C. in the Institute for Atmospheric Physics of the Academy of Sciences of the U.S.S.R. A strong helium emission at 10830 Å has been discovered in sunlit aurorae and in the ordinary twilight airglow. It is now observed regularly. A detailed theory of this fluorescent emission has been developed. Extensive observations on the hydroxyl bands between 5000 and 12,000 Å have been carried out at a number of stations. Marked seasonal and geographical variations have been found in them. During intense aurorae the line-width of the 6300 Å emission from great altitudes increases. The effect has been studied using Fabry-Perot interferometers. Contributions have been made to knowledge on auroral morphology. The interpretation of some of the results which are described in the review are discussed.     

H.E.S.S. observations of LS 5039

Recent observations of the binary system LS 5039 with the High Energy Stereoscopic System (H.E.S.S.) revealed that its Very High Energy (VHE) γ-ray emission is modulated at the 3.9 days orbital period of the system. The bulk of the emission is largely confined to half of the orbit, peaking around the inferior conjunction epoch of the compact object. The flux modulation provides the first indication of γ-ray absorption by pair production on the intense stellar photon field. This implies that the production region size must be not significantly greater than the gamma-gamma photosphere size (∼1 AU), thus excluding the large scale collimated outflows or jets (extending out to ∼1000 AU). A hardening of the spectrum is also observed at the same epoch between 0.2 and a few TeV which is unexpected under a pure absorption scenario and could rather arise from variation with phase in the maximum electron energy and/or the dominant VHE γ-ray production mechanism. This first-time observation of modulated γ-ray emission allows precise tests of the acceleration and emission models in binary systems. Mathieu de Naurois for the H.E.S.S. Collaboration.     

M.I.T. studies of transient X-ray phenomena

A variety of transient X-ray phenomena have been studied by the M.I.T. X-ray Astronomy Group. Data from the OSO-7 satellite reveal both long and short time-scale transients. Extensive observations have been made of the Lupus X-ray Nova (3U1543-47) and of GX339-4 (MX1658-48) which may represent a very different type of transient source A unique, intense X-ray flare lasting ten minutes was also recorded, and the X-ray emission from the active galaxy Cen A was found to vary significantly over a period of several days. In a recent ballon flight the Crab, pulsar, NP0532, was observed to exhibit a transient pulsed component distinct from the usual main pulse and interpulse. A sounding-rocket experiment detected an ultrasoft transient X-ray source tentatively associated with SS Cygni, and preliminary results from SAS-3 show a very hard spectrum for the new source A0535+26. On the other hand, extensive OSO-7 null observations of both Type I and II supernovae and of the flaring radio star Algol make it unlikely that these types of objects are potent transient X-ray emitters.Supported in part by the National Aeronautics and Space Administration under contracts NGL 22-009-015, NSR 22-009-654 and grant NGL 22-099-730 and by the National Science Foundation under grant GP-31378.Paper presented, at the COSPAR Symposium on Fast Transients in X- and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975.     

Analytical theory of earth's artificial satellites (A.T.E.A.S.)

The problem of A.T.E.A.S. is treated, for the zonal perturbations, in its Hamiltonian form. The method consists in eliminating angular variables from the Hamiltonian function. Nearly identity canonical transformations are used, first to remove short periodic terms, second to remove long periodic terms. The general solution, up toJ ₂ ³ , is represented by the generators of the transformations and by the mean motions of averaged variables, known up toJ ₂ ⁴ . Open expressions in the eccentricity are avoided as far as possible. It permits to obtain a closed second order theory with closed third order mean motions.Proceedings of the Sixth Conference on Mathematical Methods in Celestial Mechanics held at Oberwolfach (West Germany) from 14 to 19 August, 1978.