共查询到20条相似文献，搜索用时 93 毫秒
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将作者在变质量天体力学所得理论结果应用于太阳质量损失对流星群轨道根数变化的长期效应上。太阳质量损失包括光子辐射和太阳风造成的质量损失。利用G—M型变质量天体轨道根数变化方程的一阶和二阶解对15个流星群轨道半长轴、近日点距离、轨道周期和近日点经度因太阳质量损失造成的每世纪的长期改变效应做了数值计算,并得出计算结果。其计算结果表明,太阳质量损失使流星群轨道半长轴每世纪的改变效应较明显,它们同太阳距离的扩大影响值得关注,但对轨道周期的拉长每世纪的影响甚小,对近日点经度只有量级变化小到可以略而不计。 相似文献
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5月6日室瓶座η流星雨极盛宝瓶座η流星雨是与哈雷彗星有关的流星雨。哈雷彗星在运行到太阳附近时在其运行轨道上撒落大量流星体粒子。宝瓶座η流星群是哈雷彗星的流星群中的一个,每年4月下旬到5月下旬期间,宝瓶座流星群粒子进入地球大气 相似文献
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本文利用我国1984-1990年猎户流星雨的目视观测资料,测定猎户流星群的星等分布因子r,所得结论与国外结果一致。 相似文献
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本文由统计的观点讨论三个物理问题:(1)自转恒星的角动量的来源,(2)作一星团之内自转和空间运动的关联,(3) 超巨星是否有相当大的自转。我们的结论是一个恒星的自转角动量可能是由星胚(proto-stars)间或甚至是产生它的物质云间的碰撞引起的。理由是:(a)观测到的恒星自转和它的银线并无关联,(b)属于物理性质不同的集团的星的平均自转速度可以有很大的差别,(C)在天蝎一半人马座B型星团内的恒星自转和它们的内部运动是关联关的:对于星团本身运动得快的星有较快的自转速度。最后一节述及对于由测量得的超巨星光普线宽度推知的速度的解释。这结果和以前所提出的两种超巨星模型均无抵触。 相似文献
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海尔—波普彗星的球状喷出物 总被引：3，自引：2，他引：1
１９９６年９月观测到海尔－波普彗星的一次喷发,这次喷发持续了几天,在９月１０日和１１日分别观测到慧星的二个球状喷出物,并测得其投影喷出速度约为１００ｍ／ｓ,其后喷出物演变为巨大的喷流。 相似文献
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１９９６年９月观测到海尔－波普彗星的一次喷发,这次喷发持续了几天,在９月１０日和１１日分别观测到彗星的二个球状喷出物,并测得其投影喷出速度约为１００ｍ／ｓ,其后喷出物演变为巨大的喷流． 相似文献
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利用色球Hα、TRACE／WL、SOHO／EITEuV单色像观测资料及SOHO／MDI光球磁场观测资料，对2003年10月22日太阳活动区AR0484内发生的日浪事件进行了研究．发现：(1)在Ha线心观测上，日浪包含有亮、暗2个分量，这2个分量先后出现而且并不共空间．日浪的亮分量与UV和EUV波段上观测到的喷发具有较好的同时性和共空间性．(2)日浪喷发物质沿着EUV环运动。(3)在光球层，日浪足根处的黑子和磁场有明显的变化．这些观测结果支持日浪的磁重联模型。 相似文献
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G. O. Ryabova 《Solar System Research》2013,47(3):219-238
An analytical review of the models of ejection of meteoroids from cometary nuclei is presented. Different formulas for the ejection velocity of meteoroids and the corresponding parameters are discussed and compared with the use of comet Halley and the Geminids meteoroid stream as examples. The ejection velocities obtained from observations of the dust trails of comets are discussed, and the values for comets 2P/Encke, 4P/Faye, 17P/Holmes, 22P/Kopff, and 67P/Churyumov-Gerasimenko are compared to the velocities yielded by Whipple’s model. The uncertainty intervals of the results are estimated. 相似文献
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This paper deals with obtaining the maximum size of cometary grains ejected from nuclei of different shapes. Two mechanisms in terms of grain ejection from comets are taken into consideration. The first one is dragging of particles by outflowing gas molecules released by gentle sublimation from the comets. The second one is related with gas jets from the cavities in a nucleus by cometary jet‐like phenomena. We focused on ellipsoidal shapes of cometary nuclei but with different flattening. Calculations have been carried out for a large range of cometary parameters. It has been shown that for fixed mass of the nucleus the maximum size of grains is an increasing function of the nucleus flattening. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Solar wind propagation from the point of measurement to an arbitrary target in the heliosphere is an important input for heliospheric, planetary and cometary studies. In this paper a new kinematic propagation method, the magnetic lasso method is presented. Compared to the simple ballistic approach our method is based on reconstructing the ideal Parker spiral connecting the target with the Sun by testing a previously defined range of heliographic longitudes. The model takes into account the eventual evolution of stream–stream interactions and handles these with a simple model based on the dynamic pressure difference between the two streams. Special emphasis is given to input data cleaning by handling interplanetary coronal mass ejection events as data gaps due to their different propagation characteristics. The solar wind bulk velocity is considered radial and constant. Density and radial magnetic field are propagated by correcting with the inverse square of the radial distance. The model has the advantage that it can be coded easily and fitted to the problem; it is flexible in selecting and handling input data and requires little running time. 相似文献
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Martin Beech 《Meteoritics & planetary science》2002,37(5):649-660
Abstract— The remarkable fact about the Mazapil meteorite is that it fell on the same night, in 1885, that the Andromedid meteor shower underwent a spectacular outburst. The simultaneity of these two events has driven speculation ever since. From ?1886 to ?1950 the circumstances of the Mazapil fall were taken, by a number of researchers, as the paradigm that demonstrated the fact that comets were actually swarms of meteoritic boulders. Beginning ?1950, however, most researchers began to adopted the stance that the timing of the Mazapil fall was nothing more than pure coincidence. The reason behind this change in interpretation stemmed from, amongst other factors, the fact that none of the prominent annual meteor showers could be clearly shown to deliver meteorites. Also, with the introduction of the icy‐conglomerate model for cometary nuclei, by F. Whipple in the early 1950s, it became increasingly clear that only exceptional circumstances would allow for the presence of large meteoritic bodies in cometary streams. Further, by the mid 1960s it had been shown that meteorites could, in fact, be delivered to the Earth from the main belt asteroid region via gravitational resonances. With the removal of the dynamical “barrier” against the delivery of meteorites from the asteroid region, the idea that the Mazapil meteorite could have been part of the Andromedid stream fell into complete disfavor. This being said, we nonetheless present the results of a study concerning the possible properties of the parent object to the Mazapil meteorite based upon the assumption that it was a member of the Andromedid stream. This study is presented to illustrate the point that while cometary showers do not yield meteorites on the ground, this does not, in fact, substantiate the argument that no meteoritic bodies reside in cometary streams. Indeed, we find no good reason to suppose that an object with the characteristics of the Mazapil meteorite could not have been delivered from the Andromedid stream. However, we argue that upon the basis of the actual reported observations and upon the scientific maxim of minimized hypothesis and least assumption it must be concluded that the timing of the fall of the Mazapil meteorite and the occurrence of the Andromedid outburst were purely coincidental. 相似文献
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J Borg 《Planetary and Space Science》2002,50(9):889-894
In the context of dust samples collections in space, the COMET experiment (Collecte en Orbite de Matière ExtraTerrestre) was proposed for the first time in 1982. The idea of such an experiment was to collect grains with identified cometary parent body, instead of mixing all extraterrestrial contributions present in low Earth orbit. It was thus proposed to install collectors inside hermetic boxes, to have these boxes mounted outside a space station, orbiting the Earth and to have the capability of choosing the time and duration of the collection. Since 1985, the COMET experiment has been exposed three times to space (COMET-1, in October 1985 during the encounter of the Earth with the Draconid meteor stream; the EUROMIR-95 instrument, exposing collectors, during the crossing by the Earth of the Orionid meteor stream associated to comet P/Halley and, in November 1998, during the crossing by the Earth of the Leonid meteor stream associated to comet Temple-Tuttle, COMET-99). Specific collection techniques, and corresponding analytical procedures have been developed. The collected particles are the only ones accessible in the laboratory with a known cometary origin, before the return to Earth (2006) of the Stardust mission, which will collect cometary grains in the tails of comet Wild 2. Such a challenge justifies the tremendous efforts brought into play, and that are summarized here. 相似文献
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The cometary meteoroid ejection model of Jones and Brown [Physics, Chemistry, and Dynamics of Interplanetary Dust, ASP Conference Series
104 (1996b) 137] was used to simulate ejection from comets 55P/Tempel-Tuttle during the last 12 revolutions, and the last 9 apparitions
of 109P/Swift-Tuttle. Using cometary ephemerides generated by the Jet Propulsion Laboratory’s (JPL) HORIZONS Solar System
Data and Ephemeris Computation Service, two independent ejection schemes were simulated. In the first case, ejection was simulated
in 1 h time steps along the comet’s orbit while it was within 2.5 AU of the Sun. In the second case, ejection was simulated
to occur at the hour the comet reached perihelion. A 4th order variable step-size Runge–Kutta integrator was then used to
integrate meteoroid position and velocity forward in time, accounting for the effects of radiation pressure, Poynting–Robertson
drag, and the gravitational forces of the planets, which were computed using JPL’s DE406 planetary ephemerides. An impact
parameter (IP) was computed for each particle approaching the Earth to create a flux profile, and the results compared to
observations of the 1998 and 1999 Leonid showers, and the 1993 and 2004 Perseids. 相似文献
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The structures of the meteor streams of cometary origin—Draconids, Ursids, Perseids, and Lyrids—and the streams presumably connected with asteroids—Taurids and α-Capricornids—are compared. The comparative analysis was performed by the mass distribution of meteoroids in the stream and the activity profile for the meteors with the maximum recorded stellar magnitude +3 m and brighter. Visual observations of 1987–2008 from the database of the International Meteor Organization (IMO) and earlier sources were considered. It has been shown that the structures of the meteor streams of cometary and, presumably, asteroidal origin differ somewhat by the activity profile and the mass distribution of meteoroids in the cross-section of a stream along the Earth’s orbit. 相似文献
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In the paper, the accelerated effect of ions has been discussed. The transversal magnetic disturbance is able to bring about the magnetic annihilation and merge in some cometary area. The non-steady-state reconnection process can transform the magnetic energy of some cometary area into the kinetic energy of plasma. In addition, the two stream instability caused by both solar wind and cometary plasmas exists in Type-I tail, it can also lead the paticles to be accelerated and heated in the plasma tail. 相似文献
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Using the anchoring device of a comet lander to determine surface mechanical properties 总被引：3，自引：0，他引：3
Norbert I. Kömle Andrew J. Ball Günter Kargl Jakob Stöcker Markus Thiel Harjinder S. Jolly Masarapauya Dziruni John C. Zarnecki 《Planetary and Space Science》1997,45(12):1515-1538
Owing to the low surface gravity of the Rosetta target comet 46P/Wirtanen, a means of anchoring the Rosetta Lander to the cometary surface will be necessary. This task can be accomplished by firing an anchor into the cometary soil immediately after touchdown to prevent a rebound of the spacecraft from the surface or subsequent ejection by other forces, and to allow for mechanical activities (drilling, etc.) at the landing site.
The rationale for anchoring is examined, based on estimates of the main forces likely to act on the spacecraft after landing. We report on the development of an anchoring device using a pyrotechnic gas generator as a power source and an instrumented anchor.
In addition to the anchoring function, which is the primary purpose of this system, the integration of acceleration and temperature sensors into the tip offers the possibility to determine some important material properties of the cometary surface layer. The accelerometer is designed to measure the deceleration history of the projectile and is thus expected to give information on how the material properties (in particular strength) change within the penetrated layer(s), while the temperature sensor will measure temperature variations at the depth at which the anchor finally comes to rest. As the mechanical properties of the material are not known, it is difficult to predict the final depth of the anchor with any great certainty, but it may well be greater than that reached by any other of the lander's instruments.
The instrumented anchor will be part of the MUPUS experiment, selected to form part of the Rosetta Lander payload. We report on results of laboratory simulations of anchor penetration performed at the Institut für Weltraumforschung, Graz, and compare these with models of projectile penetration. The value of the results expected from the penetrometry experiment in the context of an improved understanding of cometary processes is discussed. 相似文献
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D. J. Asher 《Earth, Moon, and Planets》2008,102(1-4):27-33
The spatial structure of meteor streams, and the activity profiles of their corresponding meteor showers, depend firstly on
the distribution of meteoroid orbits soon after ejection from the parent comet nucleus, and secondly on the subsequent dynamical
evolution. The latter increases in importance as more time elapses. For younger structures within streams, notably the dust
trails that cause sharp meteor outbursts, it is the cometary ejection model (meteoroid production rate as a function of time
through the several months of the comet’s perihelion return, and velocity distribution of the meteoroids released) that primarily
determines the shape and width of the trail structure. This paper describes how a trail cross section can be calculated once
an ejection model has been assumed. Such calculations, if made for a range of ejection model parameters and compared with
observed parameters of storms and outbursts, can be used to constrain quantitatively the process of meteoroid ejection from
the nucleus, including the mass distribution of ejected meteoroids. 相似文献