The Earth as a planet

A comparison of the Earth with the Moon and other planets can help considerably in the solving of geophysical problems. Professor Cook deals with some of these problems in this article, which is a summary of the inaugural lecture he gave as professor of geophysics at Edinburgh on January 15.     

Images of a fourth planet orbiting HR 8799

High-contrast near-infrared imaging of the nearby star HR 8799 has shown three giant planets. Such images were possible because of the wide orbits (>25?astronomical units, where 1?au is the Earth-Sun distance) and youth (<100?Myr) of the imaged planets, which are still hot and bright as they radiate away gravitational energy acquired during their formation. An important area of contention in the exoplanet community is whether outer planets (>10?au) more massive than Jupiter form by way of one-step gravitational instabilities or, rather, through a two-step process involving accretion of a core followed by accumulation of a massive outer envelope composed primarily of hydrogen and helium. Here we report the presence of a fourth planet, interior to and of about the same mass as the other three. The system, with this additional planet, represents a challenge for current planet formation models as none of them can explain the in situ formation of all four planets. With its four young giant planets and known cold/warm debris belts, the HR 8799 planetary system is a unique laboratory in which to study the formation and evolution of giant planets at wide (>10?au) separations.     

Water vapour in the atmosphere of a transiting extrasolar planet

Water is predicted to be among the most abundant (if not the most abundant) molecular species after hydrogen in the atmospheres of close-in extrasolar giant planets ('hot Jupiters'). Several attempts have been made to detect water on such planets, but have either failed to find compelling evidence for it or led to claims that should be taken with caution. Here we report an analysis of recent observations of the hot Jupiter HD 189733b (ref. 6) taken during the transit, when the planet passed in front of its parent star. We find that absorption by water vapour is the most likely cause of the wavelength-dependent variations in the effective radius of the planet at the infrared wavelengths 3.6 mum, 5.8 mum (both ref. 7) and 8 mum (ref. 8). The larger effective radius observed at visible wavelengths may arise from either stellar variability or the presence of clouds/hazes. We explain the report of a non-detection of water on HD 189733b (ref. 4) as being a consequence of the nearly isothermal vertical profile of the planet's atmosphere.     

关于建立涡旋引力场及“水星进动”与“岁差”运行机制的统一

依据引力场与电磁场应具有的对称性,以及引力场理论应具有的完备性,即以库仑力静电场与万有引力场的对称性,以及电流产生磁场与运动物体产生涡旋引力场的对称性,建立了涡旋引力场.将万有引力与涡旋引力对行星运动的综合作用,对水星进动和地球岁差运行机制的统一性作了论证;对静止卫星轨道摄动作了分析;对太阳系多个行星的岁差作了推算;对章动的物理意义和定义作了新的探讨;并解释了涡旋引力场与旋涡星系蝶形结构形成的关系.经对涡旋引力场理论建立及与实际结合的一致性的论证表明:运动物体将产生涡旋引力场,以万有引力和涡旋引力场组成的引力系统更符合太阳系行星运行的实际,以及本文涡旋引力场理论的建立过程及结论的合理性.并在此基础上,建立了由万有引力和涡旋引力综合作用下的行星轨道模型.     

Structure of a bacterial 30S ribosomal subunit at 5.5 A resolution.

The 30S ribosomal subunit binds messenger RNA and the anticodon stem-loop of transfer RNA during protein synthesis. A crystallographic analysis of the structure of the subunit from the bacterium Thermus thermophilus is presented. At a resolution of 5.5 A, the phosphate backbone of the ribosomal RNA is visible, as are the alpha-helices of the ribosomal proteins, enabling double-helical regions of RNA to be identified throughout the subunit, all seven of the small-subunit proteins of known crystal structure to be positioned in the electron density map, and the fold of the entire central domain of the small-subunit ribosomal RNA to be determined.     

双星引力辐射的电磁学模拟

爱因斯坦的广义相对论预言了引力波的存在.根据广义相对论,引力辐射是一种四极辐射.建立一个电学模型,将电四极辐射和引力辐射进行类比,得到双星系统引力辐射功率.所得结果与广义相对论的结论只差1/4的数值因子.     

Schwarzschild外场中Proca光子的短程线方程

回顾光子静止质量上限的探测结果,得出重光子（Proca光）所遵守的电磁场方程．根据引力场中有质量粒子的短程线方程,以球对称质量外部引力场（Schwarzschild外场）为例,讨论处于其中的重光子的短程线方程,得出各方程对应的物理意义．     

转动潮汐变形双星表面重力加速度的数值模拟

转动和潮汐效应是影响双星结构演化非常重要的物理因素。在转动双星系统中,根据考虑转动潮汐变形的高阶扰动势数值计算了主星表面的重力加速度的分布,并与洛希模型计算的表面重力加速度分布做了对比。结果发现:转动和潮汐对恒星表面的重力加速度的大小和分布有重要影响,采用本文中的初始参数进行演化计算,最大影响可达到103～104 cm/s2。因此在讨论恒星结构和演化时,转动和潮汐变形是不可忽略的重要因素。     

Neptune's capture of its moon Triton in a binary-planet gravitational encounter

Triton is Neptune's principal satellite and is by far the largest retrograde satellite in the Solar System (its mass is approximately 40 per cent greater than that of Pluto). Its inclined and circular orbit lies between a group of small inner prograde satellites and a number of exterior irregular satellites with both prograde and retrograde orbits. This unusual configuration has led to the belief that Triton originally orbited the Sun before being captured in orbit around Neptune. Existing models for its capture, however, all have significant bottlenecks that make their effectiveness doubtful. Here we report that a three-body gravitational encounter between a binary system (of approximately 10(3)-kilometre-sized bodies) and Neptune is a far more likely explanation for Triton's capture. Our model predicts that Triton was once a member of a binary with a range of plausible characteristics, including ones similar to the Pluto-Charon pair.     

一个翡翠新品种的发现

在缅甸发现一个翡翠新品种——榴辉翠,其主要组成矿物为石榴石和绿辉石,是绿辉石质翡翠类的新成员,也是榴辉岩的新类型。它呈深绿色,有淡黄绿色斑点,其他宝石学特征与绿辉石质翡翠相似。用电子探针、X射线粉晶分析、红外光谱等测试手段对榴辉翠进行了详细研究。     

Discovery of a bright quasar without a massive host galaxy

A quasar is thought to be powered by the infall of matter onto a supermassive black hole at the centre of a massive galaxy. Because the optical luminosity of quasars exceeds that of their host galaxy, disentangling the two components can be difficult. This led in the 1990s to the controversial claim of the discovery of 'naked' quasars. Since then, the connection between quasars and galaxies has been well established. Here we report the discovery of a quasar lying at the edge of a gas cloud, whose size is comparable to that of a small galaxy, but whose spectrum shows no evidence for stars. The gas in the cloud is excited by the quasar itself. If a host galaxy is present, it is at least six times fainter than would normally be expected for such a bright quasar. The quasar is interacting dynamically with a neighbouring galaxy, whose gas might be feeding the black hole.     

Discovery of a comet by its Lyman-alpha emission

Several searches for near-Earth objects have recently been initiated, as a result of increased awareness of the hazard of impacts on the Earth. These programs mainly search for asteroids, so amateur astronomers can still contribute to the discovery of comets, especially out of the orbital plane of the Solar System. An ideal way to search for comets would be to use a spaceborne instrument capable of imaging the whole sky on a daily basis in a systematic and repeatable way. Such an instrument already exists on the solar observatory SOHO; it operates at the Lyman-alpha wavelength of neutral hydrogen, which is the main component of the emission cloud of a comet. Here we report the discovery, using archival data from this satellite, of a hitherto unnoticed comet which reached a perihelion of 1.546 a.u. on 26 June 1997. We derive the water production rate of the comet as a function of time and find that it increases after perihelion, like that of comet Halley.     

甘肃省首次发现泥炭藓科(Sphagnaceae)植物

Previously,more than 400 species of bryophytes in Gansu Province were reported;however,there was no any species of the moss family Sphagnaceae[1-5].In 2006,we collected a specimen of the family Sphag naceae from Baishuijiang National Nature Reserve in Gansu Province.Then three specimens of diferentcommunities were gathered again from this area in 2007.We provide the picture concerning its natural habitat in the paper(Fig.1).     

稀土-碱土金属异核配合物的合成及晶体结构

在溶剂热条件下,一种新的稀土-碱土金属异核配合物｛[Pr2（oda）6Mg2][Mg（H2O）6]·6H2O｝n （1）（H2oda=oxydiacetic acid）被成功合成,并通过X-射线单晶衍射,元素分析,红外光谱等对该配合物结构进行表征. X-射线单晶结构解析表明,该化合物属于立方晶系,Fd3ˉc空间群,晶胞参数：a=b=c=2.5967（3）nm,α=β=γ=90°,V=1.7509（4） nm3,可观测衍射点数总数为36371,独立衍射点数为840,R（int）值为0.0632,Z=8,R1=0.0262,wR2=0.0731. CCDC号为：757812.有趣的是该配合物是由两种类型的孔洞构成的离子型框架结构,两种类型孔洞分别被水合镁离子及自由水分子填充.     

含曲率平方项的引力理论的行星结构方程

建立拉格朗日密度函数为L＝根号－g(λR αRuyR^uv βR2-m)的R＋R2引力理论的多层球行星结构方程，即修正的Lane-Emden方程，并分别在多方指数N取0和1的情况下，求得结构方程的解析解，研究R＋R2引力理论对牛顿行星结构的修正。     

Clustering of the collisionless particles in a gravitational field and rotation curve

The problem of dark matter in present astrophysics has been disputed for a long time and has not been solved yet. More and more evidence shoves that mostly the dark matter is probably not baryonic, but the collisionless particles which only participate in the gravitational interaction. These collisionless particles can condense in any potential well and provide the "missing mass".