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1.
叙述了测定大气折射对工作星表的要求和星表系统误差的影响,并通过FK5星表相对于依巴谷星表的系统误差,来说明以往的各种基本星表都不适用的原因;文章说明了依巴谷星表所列星位置不含随天区而异的系统误差的特性,分析了该星表问世时的精度和十多年后的今天仍能达到的精度,说明它可以作为这种测定的工作星表,从而为直接测定天文大气折射值和折射率差提供了一个重要的条件;文章还介绍了依巴谷星表的星等分布,认为只需选用亮于6mag的依巴谷星,这一星等范围,为制定专用测量仪器终端的设计方案提供了依据。  相似文献   

2.
FK5星表和依巴谷星表的比较   总被引：2，自引：0，他引：2  
陆佩珍  须同祺 《天文学报》1999,40(1):107-112
由ＦＫ５星表和依巴谷星表在不同历元上的比较、检测和讨论了ＦＫ５星表的系统差．结果表明，ＦＫ５星表的自行系统差可能是影响ＦＫ５星表位置系统差的主要来源．在一些研究工作中，例如在依巴谷星表系统中研究地球自转的长期变化或以前的照相观测结果的重新归算，需要考虑依巴谷星表自行个别误差的影响  相似文献   

3.
本文简要介绍了欧洲空间局通过阿利亚那火箭发射的依巴谷天文卫星,也概述了为依巴谷卫星探测计划服务,并积累和编辑其观测资料的输入星表数据库。  相似文献   

4.
FK5星表系统差讨论   总被引：1，自引：0，他引：1  
比较了Ｊ２０００．９年的ＦＫ５和依巴谷结果的位置和自行,表明了ＦＫ５星表有较大的系统差。另外,我们亦将在ＦＫ５系统中的运动中和上海天文光电等高星表和依巴谷测作了比较,同样反出类似的ＦＴ５星表系统差。  相似文献   

5.
依巴谷星表在建立时已做到与以河外射电源定义的国际天球参考系（ICRS）相符合,而ICRS系统与由FK5星表实现的由J2000.0平赤道和平春分点定义的赤道坐标系统相一致。估计依巴谷星表的系统误差小于0.1mas,因此,依巴谷星表成为描述光学观测确定的地球定向参数（EOP）的一个更为均匀的参考系。本文主要讨论了FK5和依巴谷星表之间的星表系统差（FK5－Hip）,并用中国光电等高星表来检验（FK5－Hip）星表系统差的结果,并估算了星表系统差（FK5－Hip）对EOP的影响。  相似文献   

6.
我国综合授时赤经星表(简称CTC),是利用我国五个天文台站(上海天文台,紫金山天文台,北京天文台,陕西天文台以及上海天文台的海南岛临时观测站)的五个光电中星仪和一个目视中星仪测时资料综合而成的.该星表共包括星等范围为0.~m1-6.~m6,赤纬区间为-30°- 66°的1156颗恒星。该星表以FK_4星为基础进行了恒星赤经的个别改正和系统修平,未进行春分点改正和没有建立自己自行系统,因此是一个相对星表.该星表采用了3-5年的观测数据,总观测星次达76847次,从而达到了比较高的精度,尤其是在赤纬带-5°- 56°范围内的1043颗星,其定位精度一般均优于±4ms.在本文中给出了CTC星表的编算方法及其精度.由于CTC星表已专刊发表,本文仅发表CTC星表的三个台站以上观测过恒星的赤经位置(1975.0历元),观测历元,观测次数,赤经位置的总精度σ及内部精度m,以供今后星表工作参考.  相似文献   

7.
1978年初至1981年初,我们用陕台光电等高仪(Ⅰ型)进行了专门的星表观测。获得的星表包括777颗两次过等高圈的恒星的赤径改正△α和赤纬改正△δ。其中有FK4星357颗,FK4supp星189颗,GC星231颗。对于|cosq|≤0.3的星没有计算△δ。所有FK4星△α、△δ的平均精度分别为±0.0036和±0″.063。另外,还给出了43颗一次过等高圈的恒星的赤经改正△α和2颗星的赤纬改正△δ。为有效地扩充待测星数,除在时间、纬度观测纲要即基本组(2小时一组)内插入适当数目的待测星外,我们增加了星表组(1小时一组)。观测方案是:星表组——基本组——星表组——星表组——基本组——星表组或者星表组——基本组——基本组——星表组。星表的系统完全由基本组的FK4星决定。将各基本组化到平均系统以后,所有的星表组及基本组内的插入星直接相对于这个平均系统求其残差平均值。  相似文献   

8.
陕西天文台 (CSAO)和俄罗斯东西伯利亚物理技术和无线电工程测量研究所(VSNIIFTRI)之间进行的等高仪合作观测研究已进行了三年多 ,到 1 999年上半年完成了两部纲要的观测 ,获得了两部无赤纬盲区的等高仪星表。主要介绍两部纲要的观测精度 (相对依巴谷星表系统 )、星位改正精度和某些系统误差的分析。从各个方面来看 ,都达到了预期的合作目标。  相似文献   

9.
本文从明钞本和《四库全书》文津阁本《灵台秘苑》以及《文献通考》、《天文大成管窥辑要》和《天元历理全书》等五种古籍中,搜辑了宋皇祐年间的恒星(包括二十八宿距星)观测记录,审订考校,并参酌《新仪象法要》星图及南宋苏州石刻《天文图》,整理得到360颗恒星的入宿度及去极度等资料,再据此换算为A. D. 1052年的赤经与赤纬,归算出1975年的坐标,并给出与现代星表的对照。就整个系统而言,对于我国传统的283官1464星,已概括了282官1457星,仅缺少紫微左垣的“少丞”及离宫六星。这部星表的恒星位置符合中国历代文献记载,反映和代表了我国古代的星像系统,它是继《石氏星表》之后的第二部恒星星表。在中国天文学历史上,《宋皇祐星表》实为一部可靠而重要的基本星表。  相似文献   

10.
LAMOST（Large Sky Area Multi-Object Fiber Spectroscopy Telescope）的巡天战略系统的主要功能是安排观测计划,而规划巡天星表是开展所有工作的初始步骤。天文研究人员或者巡天观测人员需要从各种类型的数据库进行选星、提取和录入。使用JDBC（Java Database Connectivity）数据库访问技术,利用面向对象的编程思想,实现了一个能访问多种类型数据库、获取星表数据、数据格式转换和星表录入的工具,支持大数据量处理,为天文研究人员以及巡天观测管理人员提供帮助。  相似文献   

11.
Observations show that the geometry of the large-scale distribution of galaxies is like a self-similar sponge which can be regarded as a fractal in fractal geometry (the Sierpinski sponge) with the fractal dimensionD f=3–, =1.7–1.8 is the index in the two-point correlation function.We suggest using a new scheme to explain the origin of galaxies and large-scale structure. In our model, we assume that the density perturbations in the early Universe are adiabatic, and once they come within the horizon, they might produce the vortices of the fractal turbulence because of the Thomson drag. A model of the fractal turbulence is also given in this paper. The results obtained show that the basic characteristics of the galaxies (massM g, angular momentumJ g) and the large-scale structure (fractal dimensionD f) can be explained, if the spectrum of early perturbations is the scale-free Zeldovich spectrum.  相似文献   

12.
It is known that the observed secular accelerations of the Sun and Moon are not consistent with the tidal interactions of the Earth with the Sun and Moon. Following Dicke, the hypothesis of variable constant of gravity is adopted and expressions for the accelerations are derived. It is shown that if the theoretical ratio of the acceleration is equated the observed one, a unique value for —/G can be calculated. Adopting the accelerations obtained by Fotheringham, Newton, Muller and Stephenson, and Stephenson, it is found that — /G ranges from 1.4 × 10–11 to 3.3 × 10–11 yr–1. This estimate is consistent with the one based upon the comparison of the lunar accelerations measured with respect to atomic and ephemis times.  相似文献   

13.
In a previous paper Lyttleton (1976) has shown that the apparent secular accelerations of the Sun and Moon, as given by de Sitter, can be largely explained if the Earth is contracting at the rate required by the phase-change hypothesis for the nature of the core. More reliable values for these accelerations have since become available which warrant a redetermination of the various effects concerned on the basis of constantG, and this is first carried out in the present paper. The lunar tidal couple, which is the same whetherG is changing or not, is found to be (4.74±0.38)×1023 cgs, about three-quarters that yielded by the de Sitter values, while within the theory the Moon would take correspondingly longer to reach close proximity to the Earth at about 1.5×109 years ago.The more accurate values of the accelerations enable examination to be made of the effects that a decreasingG would have, and it is shown that a valueG/G=–3×10–11 yr–1 can be weakly satisfied compared with the close agreement found on the basis of constantG, while a value as large numerically asG/G=–6×10–11 yr–1 seems to be definitely ruled out. On the iron-core model, an intrinsic positive component of acceleration of the angular velocity cannot be reconciled at all with the secular accelerations even for constantG, and far less so ifG is decreasing at a rate suggested by any recent cosmological theory.ItG=0, the amount of contraction available for mountain-building would correspond to a reduction of surface area of about 49×106 km2 and a volume to be redistributed of 160×109 km3 if the time of collapse were 2.5×109 years ago. For earlier times, the values are only slightly reduced. IfG/G=–3×10–11 yr–1, the corresponding values are 44×106 km2 and 138×109 km3 for collapse at –2.5×109 yr, and not importantly smaller at 38×106 km2 and 122×109 km3 for collapse at –4.5×109 yr. Any of these values would suffice to account in order of magnitude for all the eras of mountain-building. An intense brief period of mountain-building on an immense scale would result from the Ramsey-collapse at whatever time past it may have occurred.  相似文献   

14.
依巴谷星表和第谷星表的特征和意义   总被引：2，自引：0，他引：2  
主要论述依巴谷星表和第谷星表的观测特征和天体测量特征,依巴谷卫星在短期内同时测定大量高精度的恒星位置,自行和视差等五个天体测量参数以及星等和色指数,依巴谷星表和第谷星表为建立高精度的光学参考系,为研究恒星的起源,演化,分布,质量,大小和光度等,为研究双星和聚星的分布和运动,为研究星系运动和星系动力学提供了大量的高精度资料,具有重要的科学意义。  相似文献   

15.
A mechanism is treated for the origin of the eccentricities of the asteroids and of Mars: secular resonances associated with the dissipation of a primitive solar nebula. The nebula is modeled as a two-dimensional disk; a closed-form, convergent integral is derived to represent its disturbing function. Dissipation of this nebula gives rise to “excitation waves”, produced by the variable location of the secular resonances, which can excite the eccentricity of Mars, and scatter asteroidal eccentricities through the observed ranges. By requiring that these ranges match the observed values as a functions of semimajor axis, one infers: (a) the primordial eccentricities of Jupiter and Saturn initially had amplitudes different from present-day values, but these amplitudes approached the present values toward the end of nebular dissipation; (b) the nebular dissipation time scale may have been of the order of (few) × 104 years as the dissipation neared completion (but this depends on the validity of linear equations which model the inherently nonlinear asteroidal eccentricity pumping); (c) it is reasonable to propose a common origin for the eccentricies of Mars and the asteroids. A simple extension of the model also accounts for the quasi-Gaussian distribution of the number density of asteroidal eccentricities.  相似文献   

16.
We propose in the present paper that the basic behaviors of newly-emerged magnetic regions (NEMR) as seen in EUV and soft X-rays from space are interpreted by the interchange instability of the magnetic field of NEMR in the global situation surrounding it.It is shown that the situation with the NEMR is unstable against the interchange instability, and a continual relaxation to the lower energy state, or a continual invasion of the magnetic flux of the NEMR to the ambient region in the form of fine bundles or thin sheets, will take place in a short time scale of 1 L/V A following the change in the boundary condition at the photosphere. The second and the final relaxation is shown to be the enhanced Joule dissipation in a time scale of hours to several days occurring in the thin current sheets on the interface of this intermingled structure which is distributed in a large volume. This hypothesis may provide an explanation for the heating of NEMR to an X-ray emitting temperature, which is otherwise rather difficult to explain. The observed fast reconnection without appreciable flares (except for some smaller brightenings) is another aspect which can be explained in the present hypothesis. Namely, since the situation with the NEMR is unstable for the interchange from the beginning, the stressed configuration is relaxed before storing appreciable energy in the form of magnetic stress and therefore without a drastic release of a large amount of stored stress energy in the form of a flare.  相似文献   

17.
Abstract— We propose that argon‐40 measured in the lunar atmosphere and that in Mercury's atmosphere is due to current diffusion into connected pore space within the crust. Higher temperatures at Mercury, along with more rapid loss from the atmosphere, will lead to a similar or smaller column abundance of argon at Mercury than at the Moon, given the same crustal abundance of potassium. Because the noble gas abundance in the mercurian atmosphere represents current effusion, it is a direct measure of the crustal potassium abundance. We assume a fractal distribution of distance to a connected pore space, with the shortest distance increasing with depth. Given this “rock size” distribution, we show that the diffusive flux is not a unique function of temperature. Even though the diffusion coefficient is an exponential function of temperature, the flux to the surface is fairly insensitive to the temperature.  相似文献   

18.
The porous state of the early Martian regolith, due to constant impact gardening by the impactors of the heavy bombardment period means this surface layer should have been able to hold pockets of subsurface water that could be responsible for runoff channel formation upon exposure to the planet's surface. This explanation of the runoff channel formation/heavy bombardment time correlation early in Mars history indicates a warm paleoclimate is not necessary in explaining the presence of runoff channels.  相似文献   

19.
The question of the survival of the planet Earth as the Sun becomes a red giant and possibly a planetary nebula depends on the maximum extent of the Sun's envelope. This study shows that if the Earth is reached by this envelope, it will be destroyed; but if it is not, it will survive. Present stellar evolution calculations imply that the Earth will be destroyed.  相似文献   

20.
The basic geochemical model of the structure of the Moon proposed by Anderson, in which the Moon is formed by differentiation of the calcium, aluminium, titanium-rich inclusions in the Allende meteorite, is accepted, and the conditions for formation of this Moon within the solar nebula models of Cameron and Pine are discussed. The basic material condenses while iron remains in the gaseous phase, which places the formation of the Moon slightly inside the orbit of Mercury. Some condensed metallic iron is likely to enter the Moon in this position, and since the Moon is assembled at a very high temperature, it is likely to have been fully molten, so that the iron can remove the iridium from the silicate material and carry it down to form a small core. Interactions between the Moon and Mercury lead to the present rather eccentric Mercury orbit and to a much more eccentric orbit for the Moon, reaching past the orbit of the Earth, establishing conditions which are necessary for capture of the Moon by the Earth. In this orbit the Moon, no longer fully molten, will sweep up additional material containing iron oxide. This history accounts in principle for the two major ways in which the bulk composition of the Moon differs from that of the Allende inclusions.Paper dedicated to Professor Harold C. Urey on the occasion of his 80th birthday on 29 April 1973.  相似文献   

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