Jupiter and Super-Earth embedded in a gaseous disc

In this paper we investigate the evolution of a pair of interacting planets – a Jupiter-mass planet and a Super-Earth with a mass of  5.5 M _⊕  – orbiting a Solar-type star and embedded in a gaseous protoplanetary disc. We focus on the effects of type I and II orbital migrations, caused by the planet–disc interaction, leading to the capture of the Super-Earth in first-order mean-motion resonances by the Jupiter. The stability of the resulting resonant system in which the Super-Earth is on the internal orbit relative to the Jupiter is studied numerically by means of full 2D hydrodynamical simulations. Our main aim is to determine the Super-Earth behaviour in the presence of the gas giant in the system. It is found that the Jupiter captures the Super-Earth into the interior 3:2 or 4:3 mean-motion resonance, and that the stability of such configurations depends on the initial positions of the planets and on the evolution of the eccentricity. If the initial separation of the orbits of the planets is larger than or close to that required for the exact resonance, the final outcome is the migration of the pair of planets at a rate similar to that of the gas giant, at least for the time of our simulations. Otherwise, we observe a scattering of the Super-Earth from the disc. The evolution of planets immersed in a gaseous disc is compared with their behaviour in the case of the classical three-body problem when the disc is absent.     

Kepler-9b、c的近2:1平运动共振分析

对多行星系统中行星周期比的统计发现,行星周期比在简单整数比2:1、3:2的右侧边缘处有明显聚集,而在其紧邻的左边有明显空缺.针对这一现象有各种不同的动力学解释. Kepler-9系统中已发现的3个行星中,行星b、c周期比约为2.03,是接近2:1共振的一个典型例子.利用关于偏心率的二阶哈密顿方程,针对只考虑长期作用和加入共振摄动两种情况,通过研究当前状态下系统在能量等高线图与相空间截面图中的位置,讨论了两行星可能的近共振状态.     

空间碎片轨道预报中动力学模型基准的选取

在不同的轨道预报场景中, 使用的动力学模型也不同. 例如, 在低轨空间碎片的预报中大气阻力是十分重要的摄动力, 而到了中高轨, 大气阻力就可以忽略不计. 如何为不同轨道类型的空间碎片选择最优(满足精度要求下的最简)动力学模型还没有系统、详尽的研究. 将对不同精度需求、不同轨道类型下的大批量轨道进行预报, 通过比较不同动力学模型下的预报结果, 给出各种预报场景的最优动力学模型建议. 可以为不同轨道类型的空间碎片在轨道预报时选择基准动力学模型提供参考或标准.     

Exoplanetary systems: The role of an equilibrium at high mutual inclination in shaping the global behavior of the 3-D secular planetary three-body problem

On the basis of a high-order (order 12) expansion of the perturbative potential in powers of the eccentricities and the inclinations, we analyze the secular interactions of two non-coplanar planets which are not in mean-motion resonance. The model is based on the planetary three-body problem which can be reduced to two degrees of freedom by the well-known elimination of the nodes [Jacobi, C.G.J., 1842. Astron. Nachr. XX, 81-102]. We introduce non-singular canonical variables which bring forward the symmetries of the problem. The main dynamical features depend on the location and stability of the equilibria which are easily found with our analytical model. We find that there exists an equilibrium when both eccentricities are zero. When the mutual inclination is small, this equilibrium is stable, but for larger mutual inclination it becomes unstable, generating a large chaotic zone and, by bifurcation, two regular regions, the so-called Kozai resonances. This analytical study which depends on only two parameters (the ratio of the semi-major axes and the mass ratio of the planets) makes possible a large survey of the problem and enables us to identify and quantify its main dynamical features, periodic orbits, regular and chaotic zones, etc. The results of our analytical model are illustrated and confirmed by numerical integrations.     

Beobachtungen Kleiner Planeten. XIII

Es wird eine Übersicht gegeben über die im Jahr 1992 auf Tautenburger Schmidtplatten gefundenen Kleinen Planeten. Es wurden 518 Objekte beobachtet und für diese 2396 Positionen gerechnet. Es handelt sich um 408 Planetoiden mit provisorischer Bezeichnung, unter denen 274 neu vergebene Bezeichnungen sind, sowie um 110 numerierte Objekte. Für 172 Tautenburger Objekte wurden Bahnen aus einer Opposition gerechnet. Für 55 im Berichtszeitraum numerierte Planeten haben Tautenburger Positionen einen Beitrag geleistet. Acht Tautenburger Planetoiden wurden numeriert (Tab. 3). A summary is given about the Minor Planet survey performed in 1992 on Tautenburg Schmidt plates. 518 asteroids were observed and 2396 positions are calculated for them. These are 408 asteroids with provisional designations (274 of them have new designations) and 110 numbered objects. One-opposition orbits have been computed for 172 Tautenburg asteroids. Tautenburg observations could give a contribution to 55 planets numbered in the period of this report. Eight Tautenburg asteroids have been numbered (Tab. 3).     

Convective radiation fluid‐dynamics: formation and early evolution of ultra low‐mass objects

The formation process of ultra low‐mass objects is some kind of extension of the star formation process. The physical changes towards lower mass are discussed by investigating the collapse of cloud cores that are modelled as Bonnor‐Ebert spheres. Their collapse is followed by solving the equations of fluid dynamics with radiation and a model of time‐dependent convection that has been calibrated to the Sun. For a sequence of cloud‐cores with 1 to 0.01 solar masses, evolutionary tracks and isochrones are shown in the mass‐radius diagram, the Hertzsprung‐Russel diagram and the effective temperaturesurface gravity or Kiel diagram. The collapse and the early hydrostatic evolution to ages of few Ma are briefly discussed and compared to observations of objects in Upper Scorpius and the low‐mass components of GG Tau. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Photographic positions of Minor Planets

Photographic precise positions of 13 minor planets obtained with the G.P.O. astrograph at E.S.O. (La Silla, Chile) in September 1987 are given.     

An infrared imaging search for low‐mass companions to members of the young nearby β Pic and Tucana/Horologium associations

We present deep high dynamic range infrared images of young nearby stars in the Tucana/Horologium and β Pic associations, all ∼10 to 35 Myrs young and at ∼10 to 60 pc distance. Such young nearby stars are well‐suited for direct imaging searches for brown dwarf and even planetary companions, because young sub‐stellar objects are still self‐luminous due to contraction and accretion. We performed our observations at the ESO 3.5m NTT with the normal infrared imaging detector SofI and the MPE speckle camera Sharp‐I. Three arc sec north of GSC 8047‐0232 in Horologium a promising brown dwarf companion candidate is detected, which needs to be confirmed by proper motion and/or spectroscopy. Several other faint companion candidates are already rejected by second epoch imaging. Among 21 stars observed in Tucana/Horologium, there are not more than one to five brown dwarf companions outside of 75 AU (1.5″ at 50 pc); most certainly only ≤5% of the Tuc/HorA stars have brown dwarf companions (13 to 78 Jupiter masses) outside of 75 AU. For the first time, we can report an upper limit for the frequency of massive planets (∼10 M_jup) at wide separations (∼100 AU) using a meaningfull and homogeneous sample: Of 11 stars observed sufficiently deep in β Pic (12 Myrs), not more than one has a massive planet outside of ∼100 AU, i.e. massive planets at large separations are rare (≤9%). (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Photographic positions of Minor Planets

Photographic precise positions of 16 minor planets obtained with the G.P.O. astrograph at E.S.O. (La Silla - Chile) in January 1988 are given.     

Revised orbital elements of minor planets

Revised orbital elements of minor planets 702 Alauda, 946 Poesia, 2395 Aho, 3051 Nantong, 3086 Kalbaugh and 4218 Demottoni are given.