他结束了人类肉眼观天的时代——谈谈科学大师伽利略与2009国际天文年

意大利科学家伽利略是历史上一位重量级的科学大师。他不仅通过一系列有关运动物体的实验,推翻了以亚里士多德为代表的传统运动观念,还自己动手制造望远镜,并第一次用它观察星空。自古以来,日月星辰像磁石吸铁一样始终吸引着人类的目光,伽利略使用望远镜观天是科学史上非同小可的事,一方面是他获得了一系列激动人心的天文新发现,以观测事实证明哥白尼“日心地动说”的正确性,另一方面,是他由此彻底结束了人类仅用肉眼观天的时代,开创了宇宙探索的历史新纪元!     

2009国际天文年(IYA)让人类和宇宙紧密相连

早在千年之前,当人们惊异于头顶那繁星浩渺的夜空时,天文学在人类强烈的求知欲望下孕育而生,成为人类文明史上最古老的科学。它伴随着人类文明的成长,并不断影响着人类文明史的发展。1609年,伽利略首次把望远镜指向天     

探索我们的宇宙——2009国际天文年

[2009年1月10日,北京]从1609年到2009年,历史从伽利略第一次将望远镜用于天文观测至今已走过了四百年。这是望远镜光荣与梦想的四百年,是人类宇宙观不断发展的四百年,是人类的目光走向137亿光年的四百年。为纪念望远镜用于天文观测这一事件,联合国宣布将2009年定为国际天文年。这是一次天文学及其对社会、文化贡献的全球庆典。     

国际天文年与天文馆

自从1609年伽利略首次将望远镜指向太空,400年来人类对宇宙的探索,让我们的世界观在这场科技变革中深受影响。2009年国际天文年的到来,无疑给世界各地的天文馆一个千载难逢的好机会。伽利略用望远镜了解星空,天文馆把伽利略了解的星空告诉观众。天文馆在国际天文年为公众建立了一个平台,国际天文年的11项基础活动,几乎都与天文馆的活动息息相关。这里,我们为大家介绍一下印度、日本和瑞典等地的活动。     

太阳系究竟有多少颗卫星

自１６０９年伽利略首次用望远镜观测天象以来,人类开始不断发现太阳系其他行星周围的卫星。木星的４颗大卫星（木卫一至四）,其亮度在５１～６３星等之间,是太阳系内除月亮以外最亮的四颗卫星,用伽利略时代的小望远镜就能清晰地看到,因此是首批确认的卫星,称为...     

望远镜有多重要（三）

伽利略在1609年制造出天文望远镜后不久,消息就传到了中国。1618年,传教士汤若望和李祖白率先翻译了《远镜说》一书,介绍了望远镜的使用、原理、构造和制作方法。根据中德科技交流中心的说法,望远镜是在1619年由德国人邓玉函首次带入中国的。另外也可见到一种说法是,1622年汤若望首次把望远镜携入了中国。     

望远镜有多重要（一）

今年是国际天文年,据说这最早是伽利略的故乡意大利提出来的,以兹纪念伽利略在四百年前首次将望远镜指向了夜空。     

“伽利略”发现木星周围的岩石小卫星

当地基望远镜使木卫的数目达到60,并可能还会增加时,伽利略木星探测器拍摄到木星一些更小卫星的图像。在“伽利略”2002年11月飞掠木卫五期间,它的恒星跟踪器——飞船上用于瞄准某颗导航星为飞船定位的望远镜发现了9个亮闪光。飞掠期间恒星跟踪器     

揭开国际天文年的序幕到北京天文馆探索宇宙

为纪念伽利略将望远镜用于天文观测400周年,联合国正式宣布2009年为国际天文年。 北京天文馆近期隆重推出由德国蔡司公司制作的“探索宇宙”节目——和伽利略一起领略宇宙魅力。同时,在老馆的东展厅引进了由意大利佛罗伦萨科学史博物馆策划主办的《伽利略望远镜》展览。为使广大读者能分享与伽利略一同探索宇宙的乐趣,我们特别邀请北京天文馆信息中心郭霞女士撰文介绍“探索宇宙”节目。同时,我们得到展览部全体同事的大力支持,将意大利《伽利略望远镜》展览画册刊印在杂志里。而《天上宫阙》一文更详细介绍了首次亮相在老馆西展厅《玩转星空》展览中的中、西星空图。百闻不如一见,若想真正体验冬月北京天文馆的热度,请到天文馆来吧？     

IPS推荐的国际天文年节目

两小片玻璃——神奇的望远镜 望远镜的历史中包含着与天文馆密切的联系。为此,在纪念伽利略使用望远镜观天400周年之际,一个献给国际天文年的天文馆节目：“两小片玻璃——神奇的望远镜”应运而生。这个节目同时制作了两种版本,分别用于传统天文馆和数字球幕天文馆。2008年在芝加哥举行的IPS大会上,该节目正式发布。     

How to compare the surface of Io to laboratory samples

Since one does not know the photometric functions of various parts of Io, one cannot convert the observed geometric albedo of the satellite to a parameter more directly measurable in the laboratory. One must therefore convert laboratory reflectances to geometric albedos before quantitative comparisons between Io's surface and a laboratory sample are made. This procedure involves determining the wavelength dependence of the sample's photometric function. For substances such as sulfur, whose reflectance varies strongly with wavelength, it is incorrect to assume that the photometric function, and hence the ratio (laboratory reflectance/geometric albedo) is independent of wavelength. To illustrate this point, measurements of the color dependence of this ratio for sulfur are presented for the specific case in which the measured laboratory reflectance is the sample's normal reflectance. In general, unless the laboratory reflectance is precisely the geometric albedo, a wavelength-dependent correction factor must be determined before the laboratory sample can be compared quantitatively with Io's surface.     

Contribution of the mantle to the lunar asymmetry

Evidence of three kinds indicates a lunar compositional asymmetry: (1) mare basalts are much more abundant on the near side; (2) the incompatible rich KREEP component is mainly observed in near-side soils; and (3) materials on the far side are less dense than those of the near side, as indicated by the 2-km offset between the center of mass and center of figure. Recent models to explain the 2-km offset are based on near-side-far-side differences in the thickness of crustal units. The most widely discussed model calls for a thickness of anorthosite ～ 24 km greater on the far side than on the near side, but no satisfactory method of generating such a large difference has been proposed. We suggest that much of the offset reflects longitudinal differences in mantle composition primarily resulting from earlier (or more rapid) crystallization of the magma ocean on what is now the far-side hemisphere. As a result, the far-side mantle would be more magnesian and thus less dense than the near-side mantle. Differences in the amount of anorthosite or the amount of crustal porosity probably make relatively small contributions to the offset. We have evaluated four scenarios: (a) If the anorthositic crust initially formed a floating continent over what is now the near side, this would have provided thermal insulation that would have reduced the near-side cooling rate. (b) Crystallization of the magma ocean while the Moon was near the Earth would have resulted in heating by earthshine, thus reducing the near-side cooling rate. (c) An asymmetric bombardment could have preferentially heated the near side. (d) A suggestion by D. Stevenson, collection of metal from the magma ocean in one hemisphere would have pushed the unmelted “core” into an asymmetric position, and resulted in earlier magma ocean crystallization in the deeper hemisphere. Our assessment is that the asymmetric “core” hypothesis is the most plausible, that the floating continent mechanism is possible, and that the Earthshine and symmetric bombardment mechanisms are not viable. An attractive feature of the asymmetric- mantle model is that it also accounts for the asymmetries in the distribution of KREEP and mare basalts. More rapid crystallization of the far side would leave urKREEP, the last dregs of the magma ocean, concentrated under the near-side crust, thus leading to the observed tendency for KREEP to be found on the near side surface. Further, the concentration of urKREEP-associated radiactive elements on the near side would result in a much lower rate of conductive cooling of the near-side mantle and thus a much longer period of basalt extrusion on the near side. The formation of basalts would also be enhanced by the presence of more fusible materials in the near-side mantle.     

Contribution to the observation of the photospheric oscillations

Observations of the 300 s photospheric oscillation on large solar surfaces (up to 520 in diameter) using a sodium optical resonance cell seem to show that the power at long horizontal wavelengths is larger than previous results would indicate. In order to get more information about the spatial distribution of the energy, a new observational method has been perfected, which will allow us to obtain the spatiotemporal power spectrum.In some of our observations, a long-period oscillation (about 40 min) appears, with an amplitude comparable to that of the 300-s oscillation, and which seems to be correlated with the occurence of chromospheric flares.     

Additions to the Theory of the Rotation of Europa

In a previous paper (The Rotation of Europa, Henrard, Celest. Mech. Dyn. Astr., 91, 131–149, 2005) we have developed a semi-analytical theory of Europa, one of the Galilean satellites of Jupiter. It is based on a synthetic theory of the orbit of Europa and is developed in the framework of Hamiltonian formalism. It was assumed that Europa is a rigid body and Jupiter a point mass. Several additional effects should be investigated in order to complete the theory. The present contribution considers the effect of the shape of Jupiter and of the gravitational pull of Io. The sensitivity of the main theory to a change in the values of the moments of inertia of Europa is also considered.     

Project of the mission to Phobos

This article provides the main scientific objectives and characteristics of the Phobos-Soil project, intended to fly to the Martian satellite Phobos, deliver its soil samples to the Earth, as well as explore Phobos, Mars, and the Martian environment with onboard scientific instruments. We give the basic parameters of the ballistic scenario of the mission, spacecraft, and some scientific problems to be solved with the help of the scientific instruments installed on the spacecraft.     

UV Capabilities to Probe the Formation of Planetary Systems: From the ISM to Planets

Planetary systems are angular momentum reservoirs generated during star formation. Solutions to three of the most important problems in contemporary astrophysics are needed to understand the entire process of planetary system formation: The physics of the ISM. Stars form from dense molecular clouds that contain ∼ 30% of the total interstellar medium (ISM) mass. The structure, properties and lifetimes of molecular clouds are determined by the overall dynamics and evolution of a very complex system – the ISM. Understanding the physics of the ISM is of prime importance not only for Galactic but also for extragalactic and cosmological studies. Most of the ISM volume (∼ 65%) is filled with diffuse gas at temperatures between 3000 and 300 000 K, representing about 50% of the ISM mass. The physics of accretion and outflow. Powerful outflows are known to regulate angular momentum transport during star formation, the so-called accretion–outflow engine. Elementary physical considerations show that, to be efficient, the acceleration region for the outflows must be located close to the star (within 1 AU) where the gravitational field is strong. According to recent numerical simulations, this is also the region where terrestrial planets could form after 1 Myr. One should keep in mind that today the only evidence for life in the Universe comes from a planet located in this inner disk region (at 1 AU) from its parent star. The temperature of the accretion–outflow engine is between 3000 and 10 ⁷ K. After 1 Myr, during the classical T Tauri stage, extinction is small and the engine becomes naked and can be observed at ultraviolet wavelengths. The physics of planet formation. Observations of volatiles released by dust, planetesimals and comets provide an extremely powerful tool for determining the relative abundances of the vaporizing species and for studying the photochemical and physical processes acting in the inner parts of young planetary systems. This region is illuminated by the strong UV radiation field produced by the star and the accretion–outflow engine. Absorption spectroscopy provides the most sensitive tool for determining the properties of the circumstellar gas as well as the characteristics of the atmospheres of the inner planets transiting the stellar disk. UV radiation also pumps the electronic transitions of the most abundant molecules (H ₂, CO, etc.) that are observed in the UV.Here we argue that access to the UV spectral range is essential for making progress in this field, since the resonance lines of the most abundant atoms and ions at temperatures between 3000 and 300 000 K, together with the electronic transitions of the most abundant molecules (H ₂, CO, OH, CS, S ₂, CO ₂ ⁺, C ₂, O ₂, O₃, etc.) are at UV wavelengths. A powerful UV-optical instrument would provide an efficient mean for measuring the abundance of ozone in the atmosphere of the thousands of transiting planets expected to be detected by the next space missions (GAIA, Corot, Kepler, etc.). Thus, a follow-up UV mission would be optimal for identifying Earth-like candidates.     

Reply to the paper

Leblanc and de la Noë used the set of data published by Mercier and Rosenberg (1974) on the type III burst at 169 MHz. They conclude that type III bursts are associated with low density coronal structures and occur in low density regions.We show that their methods cannot lead to firm conclusions; we point out some inconsistencies in their results.