偶见天龙座流星雨

我曾经作多次流星雨的观测,可一直没见过令人兴奋的场面。１９６５年我就曾观测过狮子座流星雨,可就只见到几颗流星。去年的狮子座流星雨,我们在严寒难耐的冬夜坚守观测了４个小时,也只见到１７颗流星。１９９８年６月２７日夜晚,我们偶然和天龙座流星雨相遇,一颗接...     

流星暴的航天定义

定义ZHR^*以每小时穿过1000平方公里天顶截面的，能在铝质表面打出直径不小于1厘米的弹坑的流星体数，作为流星群对航天安全威胁强度的定量标志，给出了从ZHR到ZHR^*的换算公式．用ZHR^*取代ZHR来评价20世纪90年代以来的一些强流星雨，发现1998年的贾可比尼(天龙座)流星雨对航天安全来说，是比公认的1999、2001、2002年3次狮子座流星暴强数倍的更强流星暴．     

广东南沙观狮子座流星雨

2007年11月19日,广东天文学会的刘老师通知我去做天文科普活动的工作人员。这次是观测比较著名的狮子座流星雨,仅三天时间就有130多个同好报名,而且这次参加活动的同好热情很高,没有像上次观测天龙座流星雨一样好多都去睡觉了。     

2009年狮子座流星雨前瞻

在2008年狮子座流星雨出现意想不到的爆发之后,科学家们纷纷上调了对2009年狮子座流星雨的预测规模。在消隐了7年之后,狮子座流星雨是不是又要有大活动了呢？我就不在这里卖关子啦,先天门见山地给出各科学家的预报结果：     

举办2001年狮子座流星雨摄影赛通知

鉴于2001年11月19日前后,在中国东部、中部,有可能观测到每小时标准天顶计数峰值达到一万颗以上流星的狮子座流星暴雨。为促进这一可能的、罕见的流星雨观测和保留珍贵的流星雨资料,我们决定举办《2001狮子座流星雨摄影赛》。我们在全国范围内(包括港、澳、台)征集狮子座流星雨的观测照片。来稿要求为: 1.提供拍摄有狮子座流星的5对以上     

近20年来狮子座流星雨预报进展

对近20年来狮子座流星雨的预报工作，进行了系统的阐述和分析。1998年Tempel-Tuttle彗星的回归，再度带来了狮子座流星雨的观测热，也大大促进了对狮子座流星雨预报工作的研究与验证。有的研究在时间预报准确度方面已显示出其模型的优越性，有的在流星雨的强度方面显示出一定的准确度。指出了两大类不同的方法实际上是在三维空间强调了不同的方面。将不同方法的优势结合起来，可能会使流星雨的预报更加成熟。     

从不让我们失望的双子座流星雨

由于目前正处于狮子座流星雨极大年期,狮子座流星雨自然就成为万众注目的中心。其实可供观测的大流星雨很多,常年都可观测的大流星雨就有象限座流星雨、英仙座流星雨和双子座流星雨,再加上逢极大期的流星雨,可说每年都很有一些流星雨中的“明星”,值得我们去观赏。而今天笔者所介绍的双子座流星雨就是这些“明星”中的佼佼者。 常年可见、全球可见 双子座流星雨是每年都会     

流星雨爆发的反响

2001年11月19日凌晨,曾经让爱好者们悲观失望的狮子座流星雨,出色地表现了一回。其实,几年来有关狮子座流星雨的预报和观测过程就是一个生动的科学探索过程。天文学家在不懈地探索总结流星雨的预报理论,今年又坚定地对狮子座流星雨的爆发作出判断,我们《天文爱好者》也及时作了报导;而广大爱好者中,所有坚持者都饱尝了成功的欢乐。 喜悦的心情总是希望能和大家分享。最近,观测这次流星雨的总结报告、摄影作品、心得体会等等,像雪片一样纷纷飞到我们编辑部。但是由于版面限制,我们只能选择其中的一小部分发表在这里(而且还不得不作了大量的删节)。我们还用“流星雨爆发的反响”为题,写了一篇摘编报导。挂一漏万,不妥之处,只能请求您的谅解了。至于流星雨观测数据,敬请及时上报有关组织。     

狮子座流星暴雨真的来了

根据国际流星组织和狮子座流星雨研究中心的初步统计显示,11月18日在中东和欧洲地区都观测到狮子座流星雨的大规模爆发,极大就发生在预测地球通过坦普尔塔特尔彗星轨道面时的格林尼治时间18日凌晨2点钟。狮子座流星暴雨真的来了。欧洲和中东的观测　天文学家和天文爱好者?..     

五天四夜追狮王——99狮子座流星雨观测札记

1999年的狮子座流星雨已经过去了,每小时5000颗壮观的流星雨暴发在欧洲地中海的上空,相信那里的星友们一定饱了眼福,真让人羡慕啊。位于太平洋西岸的中国大陆,处于此次狮子座流星雨活动极大的前期,有可能看到流星数量增长的过程,因此也吸引了全国各地大量的爱好者和群众观...     

Radiative association of C and P, and Si and P atoms

The rate coefficients for the formation of carbon monophosphide (CP) and silicon monophosphide (SiP) by radiative association are estimated for temperatures ranging from 300 to 14 100 K. In this temperature range, the radiative association rate coefficients are found to vary from  1.14 × 10⁻¹⁸  to  1.62 × 10⁻¹⁸ cm³ s⁻¹  and from  3.73 × 10⁻²⁰  to  7.03 × 10⁻²⁰ cm³ s⁻¹  for CP and SiP, respectively. In both cases, rate coefficients increase slowly with the increase in temperature.     

DDO photometry and metallic abundances of E and SO galaxies and globular clusters of the LMC and SMC

Metallicity of 8 E and SO galaxies as well as that of red globulars of the LMC and SMC were obtained by means of DDO integrated photometry calibrated with galactic globular clusters (Bica and Pastoriza, 1983; hereafter referred to as Paper I). A correction was obtained in order to reduce the colors of the galaxies to zero redshift. The relation metallicity vsM _V for the galaxies is analyzed (adding to our sample the observations of McClure and Van den Bergh, 1968; and Faber, 1973a). For the Magellanic Clouds we found metallicity ranging from intermediate to poor.     

Uranus and Neptune: Shape and rotation

Both Uranus and Neptune are thought to have strong zonal winds with velocities of several 100 m s⁻¹. These wind velocities, however, assume solid-body rotation periods based on Voyager 2 measurements of periodic variations in the planets’ radio signals and of fits to the planets’ magnetic fields; 17.24 h and 16.11 h for Uranus and Neptune, respectively. The realization that the radio period of Saturn does not represent the planet’s deep interior rotation and the complexity of the magnetic fields of Uranus and Neptune raise the possibility that the Voyager 2 radio and magnetic periods might not represent the deep interior rotation periods of the ice giants. Moreover, if there is deep differential rotation within Uranus and Neptune no single solid-body rotation period could characterize the bulk rotation of the planets. We use wind and shape data to investigate the rotation of Uranus and Neptune. The shapes (flattening) of the ice giants are not measured, but only inferred from atmospheric wind speeds and radio occultation measurements at a single latitude. The inferred oblateness values of Uranus and Neptune do not correspond to bodies rotating with the Voyager rotation periods. Minimization of wind velocities or dynamic heights of the 1 bar isosurfaces, constrained by the single occultation radii and gravitational coefficients of the planets, leads to solid-body rotation periods of ∼16.58 h for Uranus and ∼17.46 h for Neptune. Uranus might be rotating faster and Neptune slower than Voyager rotation speeds. We derive shapes for the planets based on these rotation rates. Wind velocities with respect to these rotation periods are essentially identical on Uranus and Neptune and wind speeds are slower than previously thought. Alternatively, if we interpret wind measurements in terms of differential rotation on cylinders there are essentially no residual atmospheric winds.     

Substructure and the cusp and fold relations

Gravitational lensing of a background source by a foreground galaxy lens occasionally produces four images of the source. The cusp and the fold relations impose conditions on the ratios of magnifications of these four-image lenses. In this theoretical investigation, we explore the sensitivity of these relations to the presence of substructure in the lens. Starting with a smooth lens potential, we add varying amounts of substructure, while keeping the source position fixed, and find that the fold relation is a more robust indicator of substructure than the cusp relation for the images. This robustness is independent of the detailed spatial distribution of the substructure, as well as of the ellipticity of the lensing potential and the presence of external shear.     

Gravity and Topography of Moon and Planets

Planetology serves the understanding on the one hand of the solar system and on the other hand, for investigating similarities and differences, of our own planet. While observational evidence about the outer planets is very limited, substantial datasets exist for the terrestrial planets. Radar and optical images and detailed models of gravity and topography give an impressive insight into the history, composition and dynamics of moon and planets. However, there exists still significant lack of data. It is therefore recommended to equip all future satellite missions to the moon and to planets with full tensor gravity gradiometers and radar altimeters.     

Fragmentation and hydration of tektites and microtektites

Abstract— An examination of data collected over the last 30 years indicates that the percent of glass fragments vs. whole splash forms in the Cenozoic microtektite strewn fields increases towards the source crater (or source region). We propose that this is due to thermal stress produced when tektites and larger microtektites fall into water near the source crater while still relatively hot (>1150 °C). We also find evidence (low major oxide totals, frothing when melted) for hydration of most of the North American tektite fragments and microtektites found in marine sediments. High-temperature mass spectrometry indicates that these tektite fragments and microtektites contain up to 3.8 wt% H₂O. The H₂O-release behavior during the high-temperature mass-spectrometric analysis, plus high CI abundances (0.05 wt%), indicate that the North American tektite fragments and microtektites were hydrated in the marine environment (i.e., the H₂O was not trapped solely on quenching from a melt). The younger Ivory Coast and Australasian microtektites do not exhibit much evidence of hydration (at least not in excess of 0.5 wt% H₂O); this suggests that the degree of hydration increases with age. In addition, we find that some glass spherules (with <65 wt% SiO₂) from the upper Eocene clinopyroxene-bearing spherule layer in the Indian Ocean have palagonitized rims. These spherules appear to have been altered in a similar fashion to the splash form K/T boundary spherules. Thus, our data indicate that tektites and microtektites that generally contain >65 wt% SiO₂ can undergo simple hydration in the marine environment, while impact glasses (with <65 wt% SiO₂) can also undergo palagonitization.     

On universal elements,and conversion procedures to and from position and velocity

An element set is advocated that is familiar (in traditional terms), and yet applicable to every type of conic-section orbit without loss of accuracy. It is not free of singularity, but this is not a serious deficiency. Conversion procedures, to and from position and velocity, are outlined, with Fortran-77 listings appended. Tests have indicated that the errors in the pair of procedures are minimal, accuracy being limited only by computer precision and the (fixed) number of iterations used in the Kepler-equation solutions.     

Radii and Albedos of four Trojan asteroids and Jovian satellites 6 and 7

Thermal radiation has been detected from four asteroids of the Trojan group, and J6 and J7, the brightest of the outer satellites of Jupiter. The six objects all have exceedingly low geometric albedos of 0.02 or 0.03 according to calculations based on their known visual brightness and the measured thermal fluxes. 624 Hektor, the largest object studied here, has a radius of 110 ± 20 km, though the exact shape of this body is in question. While the sample observed in this work is small (the total number of Trojans larger than 0.25 km in radius is about 1000), the fact that all four studied have similarly low albedos suggests that this property is characterisic of the Trojans and at least two of the outer members of Jupiter's retinue of satellites. The low surface albedo of the Trojans may preclude the proposed origin of the Jovian group of comets among these bodies according to E. Rabe. Updated tables of the dimensions of all the Jovian satellites are given.