共查询到20条相似文献，搜索用时 140 毫秒
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以光能集中度或点列分布图的情况作为衡量大望远镜光学质量的重要指标之一是目前世界广泛采用的方法。本文叙述了用改进的哈特曼法作光能集中度检验的基本原理,介绍了对我台1米RCC望远镜光能集中度检验的具体作法和一个实测结果。给出了在国产TQ—16计算机上计算的源程序。 相似文献
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本文叙述了用改进的哈特曼法作光能集中度检验的基本原理,介绍了云南天文台对1米RCC望远镜光能集中度检验的具体做法和实测结果。 相似文献
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自适应光学技术已经成为现代地基天文光学望远镜的重要部分。在世界各地的天文台中 ,许多大型光学望远镜的自适应光学系统正在建造 ,不少的系统已经投入使用。自适应光学技术经过二十多年的发展 ,取得了越来越多的令人激动的天文观测成果 ,自适应光学正在接近成熟并正向天文实际应用的阶段转化。本文根据近几年来自适应光学望远镜在天文中的应用 ,对其所取得的天文成果给予介绍 ,并讨论了自适应光学系统所能开展的天文研究课题。 相似文献
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简要介绍了我国天文界正在研制的4m大视场光学望远镜项目－LAMOST及其进展情况，LAMOST已进入详细设计阶段，其关键技术的试验仍然在进行中，开工报靠有望在近期批复。 相似文献
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爱好者朋友们的望远镜近年来，我国成人业余天文有了可喜的发展，尤其一部分成人天文爱好者都有了大口径并且光学质量较好的望远镜，可用于寻营和其它项目观测。现介绍几位爱好者朋友给广大同好，希望能对自制天文望远镜的爱好者有所启示。照片１是我国著名天文爱好者厦门... 相似文献
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应用自适应光学望远镜所取得的天文观测成果 总被引：1，自引：0，他引：1
自适应光学技术已经成为现代地基天文学学肓远镜的重要部分。在世界各地的天文台中,许多大型光学望远镜的自适应光学系统正在建造,不少的系统已经投入使用。自适应光学技术经过二十多年的发展,取得了越来越多的令人激动的天文观测成果,自适应光学正在接近成熟并正向天文实际应用的阶段转化。本文根据近几年来自适应光学望远镜在天文中的应用,对其所取得的天文成果给予介绍,并讨论了自适应光学系统所能开展的天文研究课题。 相似文献
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天文光学望远镜轴系驱动方式发展概述 总被引：4，自引：0，他引：4
该文首先介绍了已投入使用的2.5米口径以上的25架地平式光学望远镜和11架赤道式光学望远镜轴系驱动方式,并概述了天文光学望远镜轴系驱动及其相关技术的发展过程;然后对目前国际上在研的6架大型光学望远镜和预研的10架极大光学望远镜轴系所采用的驱动形式进行了归类;最后分析了未来极大光学望远镜轴系驱动的发展趋势和与之相关的研究内容. 相似文献
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A Study of Neutron Star Structure in Strong Magnetic Fields that includes Anomalous Magnetic Moments
Akira Iwamoto 《中国天文和天体物理学报》2003,3(4):359-374
We study the effect of strong magnetic fields on the structure of neutronstar. We find that if the interior field is on the same order as the surface field currently observed, then the influences of the field on the star‘s mass and radius arenegligible; if the field is as large as that estimated from the scalar virial theorem,then considerable effects will be induced. The maximum mass of the star will be increased substantially while the central density is greatly reduced. The radius of a magnetic star can be larger by about 10%～20% than a nonmagnetic star of the same mass. 相似文献
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郑桂棠 《紫金山天文台台刊》1999,18(4):380-384
紫台口径４０ｃｍ（Ｆ／７ ．５） 双筒天体照相仪,一镜筒改用ＣＣＤ 接收器。本文设计了双分离透镜改正镜,符合ＣＣＤ 的光谱响应。试验结果表明,成象质量明显提高。 相似文献
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Jeffrey L. Herfindal Joanna M. Rankin 《Monthly notices of the Royal Astronomical Society》2007,380(2):430-436
Numerous studies of the brightest Cambridge pulsar, B1133+16, have revealed little order in its individual pulses, apart from a weak 30-odd-rotation-period fluctuation feature and that some 15 per cent of the star's pulsars are 'nulls'. New Arecibo observations confirm this fluctuation feature and that it modulates all the emission, not simply the 'saddle' region. By replacing each pulse with a scaled version of the average profile, we were able to quench all subpulse modulation and thereby demonstrate that the star's 'null' pulses exhibit a similar periodicity. A subbeam carousel model with a sparse and irregular 'beamlet' population appears to be compatible with these characteristics. 相似文献
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We present X-ray images from the P78-1 satellite for a long-lasting burst at 20 cm wavelength mapped with the Very Large Array on 19 May, 1979 by Velusamy and Kundu (1981). The decimeter wave observations were originally interpreted in terms of two models, one invoking thermal electrons radiating at low harmonics of the gyrofrequency, and the other invoking mildly relativistic electrons emitting gyrosynchrotron radiation. If indeed the 20 cm source is thermal, it should also be visible in soft X-rays, while if it is nonthermal, the soft X-ray emission should be weak or spatially or temporally distinct from the 20 cm burst. We find that only one of the three 20 cm sources was approximately co-spatial with the soft X-ray source, and that it was only partially thermal. The 20 cm burst is therefore primarily decimeter type IV emission from mildly relativistic electrons of the post-flare phase. The long lifetime (? 2h) and smooth temporal variation of the burst belie its nonthermal nature and suggest continuous acceleration as well as long term storage of energetic electrons. 相似文献
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A. V. Koldoba G. V. Ustyugova M. M. Romanova R. V. E. Lovelace 《Monthly notices of the Royal Astronomical Society》2008,388(1):357-366
This work treats the matter deceleration in a magnetohydrodynamic radiative shock wave at the surface of a star. The problem is relevant to classical T Tauri stars where infalling matter is channelled along the star's magnetic field and stopped in the dense layers of photosphere. A significant new aspect of this work is that the magnetic field has an arbitrary angle with respect to the normal to the star's surface. We consider the limit where the magnetic field at the surface of the star is not very strong in the sense that the inflow is super-Alfvénic. In this limit, the initial deceleration and heating of plasma (at the entrance to the cooling zone) occurs in a fast magnetohydrodynamic shock wave. To calculate the intensity of radiative losses we use 'real' and 'power-law' radiative functions. We determine the stability/instability of the radiative shock wave as a function of parameters of the incoming flow: velocity, strength of the magnetic field, and its inclination to the surface of the star. In a number of simulation runs with the 'real' radiative function, we find a simple criterion for stability of the radiative shock wave. For a wide range of parameters, the periods of oscillation of the shock wave are of the order of 0.02–0.2 s . 相似文献
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Donat G. Wentzel 《Solar physics》1977,52(1):163-177
Hydromagnetic waves are of interest for heating the corona or coronal loops and for accelerating the solar wind. This paper enumerates some of the limitations that must be considered before hydromagnetic waves are taken seriously. In the lowest part of the corona, waves interact so that a significant fraction of the coronal wave flux should have periods as 10 s. If the problem of interest determines either a flux of wave energy or a dissipation rate, the distance that each wave mode can travel can be specified, and for at least one mode it must be consistent with the size and location of the region where the waves are to act. Heating of coronal loops observed by X-rays can be explained if the strength of the magnetic field along the loop lies within a rather narrow range and if the wave period is sufficiently short. In general, Alfvén waves travel furthest and reach high into the corona and into the solar wind. The radial variation of the magnetic field is the most important parameter determining where the waves are dissipated. Heating of coronal helmets by Alfvén waves is probable.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
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The calculation of collision probability is the foundation of collision detection and avoidance maneuver for space objects. Now an assumption of linear relative motion is usually applied in the calculation of collision probability and then the complex 3-dimensional problem can be reduced to a 2-dimensional integral of probability density function over the area of circle. However, if the relative velocity value is very small, the term of linear relative motion is not valid. So it is necessary to consider the calculation of collision probability for nonlinear relative motions. The method used to calculate collision probability for nonlinear relative motion is studied, and test cases are designed to justify the validity of this method. It is applicable to collision probability problems involving relative velocity and error covariance varying with time. The results indicate that it is necessary to calculate collision probability with this nonlinear method under certain circumstances. For example, for elliptical relative motions in Satellite Formation Flying, when the relative velocity is below 100 m/s, the relative error between the linear method and the nonlinear method exceeds 5%; for the problem of conjunction analysis of two satellites with circular orbits, when the relative velocity is below 10 m/s, the relative error is also larger than 1%. Some significant conclusions are obtained for the collision detection system of our country. 相似文献
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Stephen J. Keihm 《Icarus》1984,60(3):568-589
A detailed model of the lunar regolith is analyzed to examine the feasibility of an orbital mapping of heat flow using microwave radiometers. For regolith thermal and electrical properties which are representative of Apollo findings, brightness temperature observations in the bandλ = 5–30 cm would be required for heat flow analysis. Spectral variations shortward of 5 cm are controlled primarily by the temperature dependencies of the thermal conductivity and electrical absorption within the diurnal-varying layer. For wavelengths longer than 30 cm, unwanted emission from high impedance subregolith layers can be significant and size limitations on spacecraft radiometers is a factor. Over the 5- to 30-cm band, lunation-averaged brightness temperature increases of 2–10°K are predicted for heat flow values representative of the Apollo measurements. The magnitude of this increase depends directly on the value of regolith microwave absorption. For absorption values consistent with Apollo laboratory measurements, a spectral increase of 5°K is predicted. This value is considered marginally sufficient for an orbital heat flow measurement. However, important non-heat flow effects must be accounted for. Spectral variations can occur due to surface topography and subsurface scattering. For nadir viewing, surface roughness effects are not expected to be significant and topographic effects are nearly constant with wavelength for λ > 5cm. Volume scattering due to subsurface rock fragments can cause emission darkening of 1–6°K. However, spectral variations will not be large unless the distribution of scatterer sizes is sharply skewed. For the Moon, the most serious spurious effect appears to be emissivity variations due to the near-surface density gradient. A brightness temperature decrease of 10°K is predicted from centimeter to decameter wavelengths. If the transition from porous surface fines to compacted regolith soil occurs rapidly (within the upper 3–5 cm), most of the emissivity decrease will occur in the 5- to 30-cm wavelength band. It is recommended that complementary radar measurements be utilized to augment constraints on regolith emissivity and scattering properties. 相似文献
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《天文和天体物理学研究(英文版)》2017,(9)
The neutrino burst detected during supernova SN 1987A is explained in a strangeon star model, in which it is proposed that a pulsar-like compact object is composed of strangeons(strangeon:an abbreviation for "strange nucleon"). A nascent strangeon star's initial internal energy is calculated,with the inclusion of pion excitation(energy around 10~(53) erg, comparable to the gravitational binding energy of a collapsed core). A liquid-solid phase transition at temperature ~ 1-2MeV may occur only a few tens of seconds after core collapse, and the thermal evolution of a strangeon star is then modeled.It is found that the neutrino burst observed from SN 1987A can be reproduced in such a cooling model. 相似文献