共查询到20条相似文献，搜索用时 149 毫秒
1.
天文地球动力学中的相对论效应 总被引：3，自引：0，他引：3
天文地球动力学利用空间与地面观测手段，监测和研究地球整体与各圈层的物质运动以及它们间的相互作用，这都离不开广义相对论及的时间与空间。随着空间对地观测精度的，为了充分利用高精度观测提供的信息，在天文地球动力学的研究中必须考虑相对论效应。所涉及的相对论效应包括：（1）相对论参考系的建立，（2）在恰当的参考系中对观测者和被观测对象的相对论运动方程（平动和自转）的描述，（3）观测者和被观测对象间的电磁信号传播，（4）依赖于坐标选择的结果与具有物理意义的可观测量的转换，（5）某些基本概念在定义在广义相对论框架下的重新确认。本文对天文地球动力学中的这些相对论效应作了简要的评述。 相似文献
2.
空间VLBI与天文地球动力学 总被引：5，自引：0，他引：5
介绍了空间VLBI的精密定轨及其在天文地球动力学应用研究中的最新进展．指出因为空间VLBI的时延和时延率观测量同时涉及到射电参考系、动力学参考系和地固参考系,所以特别适合于参考系的直接连接工作．对为评价参考系连接的精度而发展的协方差分析理论也作了介绍,还分析了将时延和时延率资料用于精密定轨时遇到的困难及其解决办法． 相似文献
3.
国际天文联合会(IAU)在1991年和2000年分别通过了关于相对论天文参考系的重要决议。特别是2000年的决议,以两个互相等价的相对论N体多参考系理论:Brumberg-Kopeikin体系和Damour-Soffel-Xu体系为基础,构造了严格且自洽的一阶后牛顿(1PN)的局部参考系和全局参考系,并给出了相应的坐标变换规则。IAU2000决议发表后的10多年里,已经开始应用在一些高精度的天体测量数据处理模型中,但是其工程化应用还没有得到广泛实现,特别是目前为止我国没有将其应用到具体的天文观测或者空间探测计划中。因此有必要对IAU的相对论天文参考系理论做一个系统的解读。首先介绍了IAU在1991年给出的一个简单的相对论参考系决议;随后在第3章和第4章详细讨论了Brumberg-Kopeikin理论和Damour-Soffel-Xu体系;接着,详细给出了IAU2000年大会关于相对论参考系的决议内容;最后,讨论了IAU2000决议的工程化应用、近10多年来的理论发展以及对未来的展望。 相似文献
4.
中国天文学会天文地球动力学专业委员会,上海市天文学会和江苏省天文学会于1989年8月1—6日在浙江嵊泗联合举办了“天体测量,天体力学和大地测量中的相对论问题”(Relativity in Astrometry,Celestial Mechanics and Geodesy)研讨会。来自天体测量,天体力学,大地测量和天体物理领域的专家35人参加了会议。会议就相对论时空观,相对论参考系和相对论天体力学三个专题作了系统综述和讨论,并结合科研工作进展就VLBI,激光测距在测地工作中应用所需考虑的相 相似文献
5.
本文对相对论流体力学的基本理论及最近的进展作了统一的和连贯的叙述,以便为射电天文研 究提供一个简明扼要的基础材料。 在类星体和星系核的射电天文的观测研究中,已经揭示出那里存在着相对论运动效应(在0.1—10pc尺度范围内)。而在更大尺度上,例如最近在天鹅座A的西北射电瓣内测到了～60kpc长的射电喷流中,流动也可能是相对论性的。因此不论在小尺度还是大尺度的射电现象的研究中,都需要考虑相对论效应。这些年来,在河外射电天文学中经常要利用相对论流体力学的研究结果,有些工作直接是为射电天文而进行的。本文的目的就是根据这种需要(特别是什对射电喷流的研究的需要),对有关的相对论流体力学研究的基本结果,加以统一的和连贯的叙述,以便为射电天文的研究提供一个基础材料。 相似文献
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7.
六十年代以来,国际上相继出现了一些先进的天文观测技术,使天体测量学、空间大地测量学和地球物理学等几门学科密切地联系起来,确定地球运动及其变化,进而探索地球运动及其变化的力学机制。天文学不仅拥有近百年地面经典观测的资料,而且随着甚长基线干涉仪、激光月球和人卫测距仪、人卫多普勒技术、空间地球动力学卫星、 相似文献
8.
高精度时频信号传递是现代物理学、天文学和计量科学所需要的重要技术.要实现空间高精度时频传递必须考虑相对论效应的影响.在IAU(国际天文学联合会)2000决议提出的相对论天文参考架下,结合当今国内外微波和激光链路传递技术,考察了在信号传递过程中涉及到的相对论效应,在地心天球坐标系下提出了超高精度的相对论理论模型(1/c~4量级),可用于未来高精度频率传递试验.并在该频率不确定度的前提下结合实例对定轨精度、信号转发间隔等技术指标给出了约束条件,对于国内未来空间超高精度时频传递以及开展相关的科研任务具有较重要的参考和应用价值. 相似文献
9.
高精度时频信号传递是现代物理学、天文学和计量科学所需要的重要技术. 要实现空间高精度时频传递必须考虑相对论效应的影响. 在IAU(国际天文学联合会)2000决议提出的相对论天文参考架下, 结合当今国内外微波和激光链路传递技术, 考察了在信号传递过程中涉及到的相对论效应, 在地心天球坐标系下提出了超高精度的相对论理论模型($1/c^4$量级), 可用于未来高精度频率传递试验. 并在该频率不确定度的前提下结合实例对定轨精度、信号转发间隔等技术指标给出了约束条件, 对于国内未来空间超高精度时频传递以及开展相关的科研任务具有较重要的参考和应用价值. 相似文献
10.
简要地回顾和介绍了IAU时间尺度和参考系的历史和进展，其主要内容：（1）牛顿时空观和相对论时空观，（2）IAU各种时间尺度的历史演变和相互关系；（3）IAU的天文参考系，有关的最新决议,相对论框架下度规及其规范问题，四维时空中的空间1PN坐标变换，也介绍了一些有关工作，阐明了与IAU最新决议稍有不同的观点，指出目前IAU有关决议可能仍存在的某种程度上的不完善。 相似文献
11.
This paper deals with a self-consistent relativistic theory of time scales in the Solar system based on the construction of the hierarchy of dynamically non-rotating harmonic reference systems for a four-dimensional space-time of general relativity. In our approach barycentric (TB) and terrestrial (TT) times are regarded as the coordinate times of barycentric (BRS) and geocentric (GRS) reference systems, respectively, with an appropriate choice of the units of measurement. This enables us to avoid some of the inconsistencies and ambiguities of the definitions of these scales as these are currently applied. International atomic time (TAI) is shown to be the physical realization of TT on the surface of the Earth. This realization is achieved by a specific procedure to average the readings of atomic clocks distributed over the terrestrial surface, all of them synchronized with respect to TT. Extending TAI beyond the Earth's surface may be performed along a three-dimensional hypersurface TT = const. The unit of measurement of TAI coincides with TB and TT units and is equal to the SI second on the surface of the geoid in rotation. Due to the specific choice of the units of measurement the TB scale differs from the TT (TAI) scale only by relativistic nonlinear and periodic terms resulting from the planetary and lunar theories of motion. The proper time 0 of any terrestrial observer coincides with the coordinate time of the corresponding topocentric reference system (TRS) evaluated at its origin. 0 is reacted to TT (TAI) by the relativistic transformation involving the GRS velocity of the observer, its height above the geoid and the quadrupole tidal gravitational potential of the external masses. The impact of introducing TB and TT on the units of measurement of length and the basic astronomical constants is discussed. 相似文献
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Goran Damljanovi? 《Planetary and Space Science》2008,56(14):1896-1902
The Commission 19 (Earth Rotation) of the International Astronomical Union—IAU established the Working Group on Earth Rotation in the Hipparcos Reference Frame—WG ERHRF at 1995 to collect the optical observations of latitude and universal time variations, made during 1899.7-1992.0 in line with Earth orientation programmes (to derive Earth Orientation Parameters—EOP), with Dr. Jan Vondrák (Astronomical Institute of Academy of Sciences of the Czech Republic, Prague) as the head of WG ERHRF. Dr. Vondrák collected about 4.4 million optical observations of latitude/universal time variations made at 33 observatories. These data were used for EOP investigations, Hipparcos Catalogue—radio sources connection, etc. Nowadays, it is used to correct the positions and proper motions of stars of Hipparcos Catalogue (as an optical reference frame) using ground-based observations of some Hipparcos stars. After Hipparcos Catalogue, some new astrometric catalogues appeared (as ARIHIP, EOC-2, etc.) with better accuracy of proper motions. We use the latitude observations made by visual zenith-telescope (ZT), as classical astrometric instrument, at seven observatories (all over the world) of International Latitude Service—ILS. The observations were used in the programmes of monitoring the Earth orientation during the 20th century. We received the data from Dr. Vondrák via private communication. The observatories are Carloforte—CA, Cincinnati—CI, Gaithersburg—GT, Kitab—KZ, Mizusawa—MZZ, Tschardjui—TS and Ukiah—UK. The task is to improve proper motions in declination of the observed Hipparcos stars. The original method was developed. We removed from the instantaneous observed latitudes, all known effects (polar motion and some local instrumental errors), and the corrected latitudes were then the input data to calculate the corrections of Hipparcos proper motions in declination using the least squares method—LSM with the linear model. We did an improvement of Hipparcos proper motions in declination via mentioned latitude variations with time by using a long-term (a few decades) visual zenith-telescope data of ILS. The calculated results were compared with the ARIHIP and EOC-2 data, and the consistency were good. The main steps of the calculations and some of the results are presented here. 相似文献
14.
本文评述了在建立历表参考架和恒星参考架过程中所面临的问题和困难，回顾了建立河外射电天球参考架的发展历史，并介绍了其目前状况，讨论了河外射电天球参考架在与其他天球参考架连接过程中所遇到的问题及其可能的解决途径。 相似文献
15.
Heinrich Eichhorn 《Celestial Mechanics and Dynamical Astronomy》1987,43(1-4):237-241
This sketch is based on the following line of thought. If we understand by (physical or dynamical) time the independent variable in the equations of motion, only quantities which are in a strictly linear relationship with this mechanical — physical time should properly be called time. This excludes therefore such concepts as e.g., sidereal time; in general that Earth Rotation Parameter which is one of the angles which define the orientation in space of a coordinate system fixed in a rigid model Earth. The relationships between these Eulerian angles and the ERP which follow from the theory of motion are discussed, also for the case that the reference system is an arbitrary noninertial system whose relationship (as a function of time) with an inertial system is known. 相似文献
16.
By now there is no doubt that the gamma-ray bursts (GRB) have a cosmological origin. This allows to regard GRB as the most
powerful known energy sources, ε∼ 1054 erg (with a total number of gamma quanta N_γ∼ 1060). A plausible mechanism of coherent synchrotron radiation (CSR) of relativistic electrons driven by a local magnetic field
is studied in this paper. We consider relativistic electrons arising in the Compton scattering of a GRB in directions close
to that of the ray from the source to a ground-based observer. The synchrotron pulses from Compton electrons located at different
points on the line between the GRB source and the observer arrive at the observation point simultaneously. This simultaneity
ensures the coherence of the detected radiation. Both molecular clouds in the host galaxy of the GRB and our own Galaxy, as
well as the Earth atmosphere are assumed to be scatterers of the GRB radiation. Signals of each scatterer reach the Earth
surface, and can be detected at radio wavelengths. We estimate the characteristics of this radiation. The comparison of GRB
data with the corresponding information on CSR pulses offers a way to determine some global characteristics of the medium
between the Earth and the GRB source. 相似文献
17.
R. T. Gangadhara 《Astrophysics and Space Science》1995,232(2):327-336
Pulsars accelerate the charged particles moving along their magnetic field lines due to their rapidly spinning motion. Particles gain maximum energy from pulsars within the light cylinder when they are moving along the field lines perpendicular to the rotation velocity. In pulsars with non-aligned rotation and magnetic axes, the production of two intense and sharp pulses (main pulse and interpulse) separated by 180° longitude occur at the two regions near the light cylinder where the rotation velocity is perpendicular to the magnetic field. Since the radiating particles move radially along the relativistically compressed magnetic field lines, the observer in the stationary frame receives beamed and transversely compressed radiation pulse. Near the light cylinder position angle varies smoothly during pulsar rotation in a way as Radhakrishnan and Cook (1969) expect its variation near the magnetic pole, as the field lines experience relativistic compression in the direction of rotation. The motion of two charge species along the field lines produce orthogonal modes at each pulse longitude. 相似文献
18.
E. H. Dowdye 《Astronomische Nachrichten》2007,328(2):186-191
Intense observations of the galactic center since 1992 have revealed the presence of a supermassive object located there, some 26 000 light years from Earth. The mass of the galactic center was determined using time resolved astrometry over a time span of 13 years, from 1992 to present. The observations clearly show that the stars in the immediate vicinity of the supermassive galactic center, denoted as Sagittarius A* (Sgr A*), move along purely Keplerian orbits around Str A*. Observation of the rapidly moving stars permitted astrophysicists to determine a mass for the galactic center of around 3.6 million solar masses. Time resolved images of the Keplerian motions of these stars has exhibited to date no evidence of distortions in the images due to gravitational light bending effects, as predicted by General Relativity. In this paper, a well known tool commonly used by astrophysicists for estimating the effect of gravitation on light rays was examined. The results reveal flaws in the understanding of fundamental principles in mathematical physics applied to gravitational effects on rays of light, as predicted by General Relativity, at the site of a point‐like gravitating masses such as the galactic center mass. Application of the Gauss Law to point‐like gravitating masses shows that a requirement for the colinear alignment of the light source, the lensing and the observer is not necessary for an observation of gravitational lensing as predicted by General Relativity. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
19.
We are carrying out a project to calculate power spectra of variability, assuming a model of a ‘spotted’ accretion disc near a black hole. We consider relativistic effects that change photon energy and produce light‐bending and time‐delays acting on the X‐ray signal received by an observer. We assume that the life‐time and the intrinsic emissivity of individual.aring events are described in terms of a simple stochastic process. This allows us to give approximate analytical formulae and compare them with numerical computations. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
20.
Application of boundary value techniques in the case of an electron performing relativistic motions within a magnetic dipole such as that of the Earth supplemented by a scanning process by means of which the entire phase space of the problem can be investigated, six new types of periodic motion have been discovered and computed. The stability of these motions is investigated and their direct bearing on formation and shape of the Van Allen zones of the Earth is discussed. 相似文献