共查询到19条相似文献,搜索用时 169 毫秒
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郭守敬,字若思,河北省邢台人,生于231年,卒于1316年(2011年是郭守敬诞辰1780年),元代杰出的科学家,在天文、数学、水利、仪器仪表制造等方面为人类科学事业的发展作出了杰出的贡献。 相似文献
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当月亮运行到地球和太阳之间,同时三者又恰好在一条视线上,从地球上看去,月亮遮住了太阳,于是发生了日食。同样的道理,当月亮遮住的天体是比较远的行星时,这种天象就叫月掩行星。几百年前,天文学家用望远镜观测月掩星时就已发现被掩的恒星是瞬息即逝地立即消失,而后又干净利落地复现。如果月亮是个有大气层的天体,当月掩星之前,将要被掩的恒星的亮度会逐渐减弱并消失在月亮的东边缘;过一会,被掩的恒星会从月亮的西边缘出现并一点点变亮。正因为没有观测到这种现象,所以从那时起人们已知道, 相似文献
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最近几年,欧洲、日本、俄罗斯、印度、英国、德国和韩国纷纷制定了新的探月计划,并逐步开始实施,从而在全世界掀起了新一轮探月热潮。近年来人类探索月球的热情之所以逐渐高涨,原因是多方面的,其中月球上汇集的历史谜团、独特的自然环境和丰富的资源,是相关国家下决心探月的重要原因。 相似文献
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对地月系统而言, 在很大程度上角动量守恒是正确的. 地月距离的变化主要是受到月球引起的潮汐能量耗散的影响. 根据月球的平均运动和它的长期加速度, 就可以计算出月潮能量耗散的数值. 海洋是潮汐能量耗散的主要区域. 由于潮汐的高度正比于月球对潮汐隆起的万有引力, 由此可导出总的月球潮汐摩擦力正比于月球平均运动的平方. 如果采用月球平均加速度数值-20.72$''\cdot$cy-2, 就可以推算出35亿年来地月之间的距离以及回归年日数和朔望月日数的演化. 此理论结果与古生物钟的数据进行比对, 两者符合较好. 相似文献
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傣族历法是自成体系的阴阳合历, 其中的干支纪日纪年法是重要的组成部分, 并与汉族历法有渊源关系, 既保留有古汉语的读音, 又继承着称为“母子”的习惯。对其由来, 以往的一些讨论并未得到圆满的解释, 本文从迁徙史的角度提出, 傣族历法中的干支等内容, 是其先民从中原迁徙而带入今云南傣族地区。 相似文献
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Highly accurate W BV R photometric measurements of the eclipsing binary HP Aur were performed in 2002–2003 with the 48-cm AZT-14 reflector at the Tien-Shan High-Altitude Observatory to determine the rate of apsidal motion. A consistent system of physical and geometrical parameters of the components and the binary as a whole has been constructed for the first time by analyzing these new measurements together with other published data: we determined their radii (R1 = 1.05R⊙, R2 = 0.82R⊙) and luminosities (L1 = 1.10L⊙, L2 = 0.46L⊙), spectral types (G2V + G8V) and surface gravities (log g1 = 4.38, log g2 = 4.51), age (t = 9.5 × 109 yr), and the distance to the binary (d = 197 pc). We detected an ultraviolet excess in the spectra of both components, \(\Delta (W - B) \simeq - 0\mathop .\limits^m 25\), that is probably attributable to a metal deficiency in the atmospheres of these stars. In this system of two solar-type stars, we found a third body with the mass M3 sin i 3 3 = 0.17M⊙ that revolved with the period P3 = 13.7 yr around the eclipsing binary in a highly eccentric elliptical orbit: e3 = 0.70 and A3 sin i3 ? 7 AU. The orbit of the eclipsing binary itself was shown to be also elliptical, but with a low eccentricity (e = 0.0025(5)), while apsidal motion with a period Uobs > 80 yr was observed at a theoretically expected period Uth ≈ 92 yr. At least 20 to 30 more years of photoelectric measurements of this star will be required to reliably determine Uobs. 相似文献
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P. Vivekananda Rao M. B. K. Sarma B. V. N. S. Prakash Rao 《Journal of Astrophysics and Astronomy》1991,12(3):225-263
Results of analysis of photoelectric observations of the RS CVn eclipsing binary WY Cancri in the standard passbands ofUBV during 1973-74, 1976-79 and inUBVRI during 1984-86 are reported. A preliminary analysis of the eclipses suggested the primary eclipse to be transit. A study
of the percentage contribution of the distortion wave amplitudes in all the colours with respect to the luminosities of both
components, showed the hotter component to be the source of the distortion wave. The clean (wave removed) light curves of
different epochs have not merged, suggesting residual effects of spot activity. The reason for this is attributed to the presence
of either (1) polar spots or (2) small spots uniformly distributed all over the surface of the hotter component. This additional
variation is found to have a periodicity of about 50 years or more. The distortion waves in yellow colour are modelled according
to Budding’s (1977) method. For getting the best fit of the observations and theory, it was found necessary to assume three
or four spots on the surface of the hot component. Out of these four spot groups, three are found to have direct motion with
migration periods of 1.01, 1.01 and 2.51 years while the fourth one has a retrograde motion with a migration period of 3.01
years. From these periods and the latitudes of the spots derived from the model a co-rotating latitude of 4ℴ is obtained.
The temperatures of these spots are found to be lower than that of the photosphere by about 700ℴK to 800ℴK. Assuming the light
curve of 1985-86, which is the brightest of all the observed seasons, to be least affected by the spots, the light curves
of the other seasons are all brought up to the quadrature level of this season by applying suitable corrections. The merged
curves in theUBVRI colours are analysed for the elements by the Wilson-Devinney method. This analysis yielded the following absolute elements:
相似文献
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Report of the International Astronomical Union Division I Working Group on Precession and the Ecliptic 总被引:1,自引:0,他引:1
J. L. Hilton N. Capitaine J. Chapront J. M. Ferrandiz A. Fienga T. Fukushima J. Getino P. Mathews J.-L. Simon M. Soffel J. Vondrak P. Wallace J. Williams 《Celestial Mechanics and Dynamical Astronomy》2006,94(3):351-367
The IAU Working Group on Precession and the Equinox looked at several solutions for replacing the precession part of the IAU
2000A precession–nutation model, which is not consistent with dynamical theory. These comparisons show that the (Capitaine
et al., Astron. Astrophys., 412, 2003a) precession theory, P03, is both consistent with dynamical theory and the solution most compatible with the IAU 2000A
nutation model. Thus, the working group recommends the adoption of the P03 precession theory for use with the IAU 2000A nutation.
The two greatest sources of uncertainty in the precession theory are the rate of change of the Earth’s dynamical flattening,
ΔJ2, and the precession rates (i.e. the constants of integration used in deriving the precession). The combined uncertainties
limit the accuracy in the precession theory to approximately 2 mas cent−2.
Given that there are difficulties with the traditional angles used to parameterize the precession, zA, ζA, and θA, the working group has decided that the choice of parameters should be left to the user. We provide a consistent set of parameters
that may be used with either the traditional rotation matrix, or those rotation matrices described in (Capitaine et al., Astron.
Astrophys., 412, 2003a) and (Fukushima Astron. J., 126, 2003).
We recommend that the ecliptic pole be explicitly defined by the mean orbital angular momentum vector of the Earth–Moon barycenter
in the Barycentric Celestial Reference System (BCRS), and explicitly state that this definition is being used to avoid confusion
with previous definitions of the ecliptic.
Finally, we recommend that the terms precession of the equator and precession of the ecliptic replace the terms lunisolar precession and planetary precession, respectively. 相似文献
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J. Hamel 《Astronomische Nachrichten》2009,330(6):526-535
In the beginning Copernicus' system of the world did not have empirical confirmation. In this situation, Kepler's research, as well as the astronomical observations with the telescope, invented in 1608, played a decisive role. Under the assumption of the central position of the Sun, Kepler discovered the elliptical orbital motion of the planets as a base of the computation of noticeably improved ephemerides. The first telescopic observations – Jupiter's moons, phases of Venus, sunspots, surface features of the moon, gave important arguments for Copernicus' system. Galilei was one of the first who used the telescope for astronomical research (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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The evolution of the current sheet in the electric current direction (in the guiding magnetic field direction) is studied
numerically in the 3-D particle-in-cell model with two current sheets and periodic boundary conditions. In the regime with
(where v
D and
are the electric current drift and electron thermal velocities, respectively) the current sheets are unstable owing to the
Buneman and kink instabilities and become strongly fragmented. During their evolution, in addition to an increase of the energy
of the electric field component in the guiding magnetic field direction, the energies of the electric field components in
the perpendicular direction are even more enhanced. In the current sheet the anomalous resistivity (η
anom/η
C∼7×105, where η
C is the classical resistivity) is generated and thus the magnetic field dissipates. Most of the dissipated magnetic energy
is transformed into the electron kinetic energy in the direction of the electric current. The associated electric field accelerates
the electrons from the tail of the distribution function. 相似文献
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We present submillimeter observations of 12CO J=3-2 and 2-1, and 13CO J=2-1 lines of the Venusian mesosphere and lower thermosphere with the Heinrich Hertz Submillimeter Telescope (HHSMT) taken around the second MESSENGER flyby of Venus on 5 June 2007. The observations cover a range of Venus solar elongations with different fractional disk illuminations. Preliminary results like temperature and CO abundance profiles are presented.These data are part of a coordinated observational campaign in support of the ESA Venus Express mission. Furthermore, this study attempts to contribute to cross-calibrate space- and ground-based observations, to constrain radiative transfer and retrieval algorithms for planetary atmospheres, and to a more thorough understanding of the global patters of circulation of the Venusian atmosphere. 相似文献
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marta Folgueira Jean Souchay Hiroshi Kinoshita 《Celestial Mechanics and Dynamical Astronomy》1998,70(3):147-157
In this paper, we make a study about the influence of the coefficients of the geopotential C4,m and S4,m, (m=1,2,3,4) on the nutation, starting from the Hamiltonian theory as developed by Kinoshita (1977).We obtain ten coefficients
larger than 0.05 μ as for the nutation in longitude and six for the nutation in obliquity. The present results are included
in the reconstruction of the theory of nutation (REN‐2000) at the level of truncation of 0.1 μ as (Souchay et al., 1997).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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